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d2d6c096f6
This adds two new settings BindPaths= and BindReadOnlyPaths=. They allow defining arbitrary bind mounts specific to particular services. This is particularly useful for services with RootDirectory= set as this permits making specific bits of the host directory available to chrooted services. The two new settings follow the concepts nspawn already possess in --bind= and --bind-ro=, as well as the .nspawn settings Bind= and BindReadOnly= (and these latter options should probably be renamed to BindPaths= and BindReadOnlyPaths= too). Fixes: #3439
1953 lines
114 KiB
XML
1953 lines
114 KiB
XML
<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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||
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="systemd.exec">
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<refentryinfo>
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<title>systemd.exec</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd.exec</refentrytitle>
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<manvolnum>5</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd.exec</refname>
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<refpurpose>Execution environment configuration</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename><replaceable>service</replaceable>.service</filename>,
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<filename><replaceable>socket</replaceable>.socket</filename>,
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<filename><replaceable>mount</replaceable>.mount</filename>,
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<filename><replaceable>swap</replaceable>.swap</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>Unit configuration files for services, sockets, mount
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points, and swap devices share a subset of configuration options
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which define the execution environment of spawned
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processes.</para>
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<para>This man page lists the configuration options shared by
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these four unit types. See
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<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for the common options of all unit configuration files, and
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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and
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<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for more information on the specific unit configuration files. The
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execution specific configuration options are configured in the
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[Service], [Socket], [Mount], or [Swap] sections, depending on the
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unit type.</para>
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<para>In addition, options which control resources through Linux Control Groups (cgroups) are listed in
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<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
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Those options complement options listed here.</para>
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</refsect1>
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<refsect1>
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<title>Automatic Dependencies</title>
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<para>A few execution parameters result in additional, automatic
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dependencies to be added.</para>
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<para>Units with <varname>WorkingDirectory=</varname> or
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<varname>RootDirectory=</varname> set automatically gain
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dependencies of type <varname>Requires=</varname> and
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<varname>After=</varname> on all mount units required to access
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the specified paths. This is equivalent to having them listed
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explicitly in <varname>RequiresMountsFor=</varname>.</para>
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<para>Similar, units with <varname>PrivateTmp=</varname> enabled
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automatically get mount unit dependencies for all mounts
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required to access <filename>/tmp</filename> and
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<filename>/var/tmp</filename>.</para>
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<para>Units whose standard output or error output is connected to <option>journal</option>, <option>syslog</option>
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or <option>kmsg</option> (or their combinations with console output, see below) automatically acquire dependencies
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of type <varname>After=</varname> on <filename>systemd-journald.socket</filename>.</para>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<variablelist class='unit-directives'>
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<varlistentry>
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<term><varname>WorkingDirectory=</varname></term>
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<listitem><para>Takes a directory path relative to the service's root directory specified by
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<varname>RootDirectory=</varname>, or the special value <literal>~</literal>. Sets the working directory for
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executed processes. If set to <literal>~</literal>, the home directory of the user specified in
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<varname>User=</varname> is used. If not set, defaults to the root directory when systemd is running as a
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system instance and the respective user's home directory if run as user. If the setting is prefixed with the
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<literal>-</literal> character, a missing working directory is not considered fatal. If
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<varname>RootDirectory=</varname> is not set, then <varname>WorkingDirectory=</varname> is relative to the root
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of the system running the service manager. Note that setting this parameter might result in additional
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dependencies to be added to the unit (see above).</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>RootDirectory=</varname></term>
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<listitem><para>Takes a directory path relative to the host's root directory (i.e. the root of the system
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running the service manager). Sets the root directory for executed processes, with the <citerefentry
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project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>2</manvolnum></citerefentry> system
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call. If this is used, it must be ensured that the process binary and all its auxiliary files are available in
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the <function>chroot()</function> jail. Note that setting this parameter might result in additional
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dependencies to be added to the unit (see above).</para>
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<para>The <varname>PrivateUsers=</varname> setting is particularly useful in conjunction with
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<varname>RootDirectory=</varname>. For details, see below.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>User=</varname></term>
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<term><varname>Group=</varname></term>
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<listitem><para>Set the UNIX user or group that the processes are executed as, respectively. Takes a single
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user or group name, or numeric ID as argument. For system services (services run by the system service manager,
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i.e. managed by PID 1) and for user services of the root user (services managed by root's instance of
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<command>systemd --user</command>), the default is <literal>root</literal>, but <varname>User=</varname> may be
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used to specify a different user. For user services of any other user, switching user identity is not
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permitted, hence the only valid setting is the same user the user's service manager is running as. If no group
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is set, the default group of the user is used. This setting does not affect commands whose command line is
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prefixed with <literal>+</literal>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>DynamicUser=</varname></term>
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<listitem><para>Takes a boolean parameter. If set, a UNIX user and group pair is allocated dynamically when the
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unit is started, and released as soon as it is stopped. The user and group will not be added to
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<filename>/etc/passwd</filename> or <filename>/etc/group</filename>, but are managed transiently during
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runtime. The <citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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glibc NSS module provides integration of these dynamic users/groups into the system's user and group
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databases. The user and group name to use may be configured via <varname>User=</varname> and
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<varname>Group=</varname> (see above). If these options are not used and dynamic user/group allocation is
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enabled for a unit, the name of the dynamic user/group is implicitly derived from the unit name. If the unit
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name without the type suffix qualifies as valid user name it is used directly, otherwise a name incorporating a
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hash of it is used. If a statically allocated user or group of the configured name already exists, it is used
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and no dynamic user/group is allocated. Dynamic users/groups are allocated from the UID/GID range
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61184…65519. It is recommended to avoid this range for regular system or login users. At any point in time
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each UID/GID from this range is only assigned to zero or one dynamically allocated users/groups in
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use. However, UID/GIDs are recycled after a unit is terminated. Care should be taken that any processes running
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as part of a unit for which dynamic users/groups are enabled do not leave files or directories owned by these
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users/groups around, as a different unit might get the same UID/GID assigned later on, and thus gain access to
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these files or directories. If <varname>DynamicUser=</varname> is enabled, <varname>RemoveIPC=</varname>,
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<varname>PrivateTmp=</varname> are implied. This ensures that the lifetime of IPC objects and temporary files
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created by the executed processes is bound to the runtime of the service, and hence the lifetime of the dynamic
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user/group. Since <filename>/tmp</filename> and <filename>/var/tmp</filename> are usually the only
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world-writable directories on a system this ensures that a unit making use of dynamic user/group allocation
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cannot leave files around after unit termination. Moreover <varname>ProtectSystem=strict</varname> and
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<varname>ProtectHome=read-only</varname> are implied, thus prohibiting the service to write to arbitrary file
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system locations. In order to allow the service to write to certain directories, they have to be whitelisted
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using <varname>ReadWritePaths=</varname>, but care must be taken so that UID/GID recycling doesn't
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create security issues involving files created by the service. Use <varname>RuntimeDirectory=</varname> (see
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below) in order to assign a writable runtime directory to a service, owned by the dynamic user/group and
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removed automatically when the unit is terminated. Defaults to off.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>SupplementaryGroups=</varname></term>
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<listitem><para>Sets the supplementary Unix groups the
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processes are executed as. This takes a space-separated list
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of group names or IDs. This option may be specified more than
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once, in which case all listed groups are set as supplementary
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groups. When the empty string is assigned, the list of
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supplementary groups is reset, and all assignments prior to
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this one will have no effect. In any way, this option does not
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override, but extends the list of supplementary groups
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configured in the system group database for the
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user. This does not affect commands prefixed with <literal>+</literal>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>RemoveIPC=</varname></term>
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<listitem><para>Takes a boolean parameter. If set, all System V and POSIX IPC objects owned by the user and
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group the processes of this unit are run as are removed when the unit is stopped. This setting only has an
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effect if at least one of <varname>User=</varname>, <varname>Group=</varname> and
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<varname>DynamicUser=</varname> are used. It has no effect on IPC objects owned by the root user. Specifically,
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this removes System V semaphores, as well as System V and POSIX shared memory segments and message queues. If
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multiple units use the same user or group the IPC objects are removed when the last of these units is
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stopped. This setting is implied if <varname>DynamicUser=</varname> is set.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>Nice=</varname></term>
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<listitem><para>Sets the default nice level (scheduling
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priority) for executed processes. Takes an integer between -20
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(highest priority) and 19 (lowest priority). See
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<citerefentry><refentrytitle>setpriority</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for details.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>OOMScoreAdjust=</varname></term>
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<listitem><para>Sets the adjustment level for the
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Out-Of-Memory killer for executed processes. Takes an integer
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between -1000 (to disable OOM killing for this process) and
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1000 (to make killing of this process under memory pressure
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very likely). See <ulink
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url="https://www.kernel.org/doc/Documentation/filesystems/proc.txt">proc.txt</ulink>
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for details.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>IOSchedulingClass=</varname></term>
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<listitem><para>Sets the I/O scheduling class for executed
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processes. Takes an integer between 0 and 3 or one of the
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strings <option>none</option>, <option>realtime</option>,
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<option>best-effort</option> or <option>idle</option>. See
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<citerefentry><refentrytitle>ioprio_set</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for details.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>IOSchedulingPriority=</varname></term>
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<listitem><para>Sets the I/O scheduling priority for executed
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processes. Takes an integer between 0 (highest priority) and 7
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(lowest priority). The available priorities depend on the
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selected I/O scheduling class (see above). See
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<citerefentry><refentrytitle>ioprio_set</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for details.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>CPUSchedulingPolicy=</varname></term>
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<listitem><para>Sets the CPU scheduling policy for executed
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processes. Takes one of
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<option>other</option>,
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<option>batch</option>,
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<option>idle</option>,
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<option>fifo</option> or
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<option>rr</option>. See
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<citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for details.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>CPUSchedulingPriority=</varname></term>
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<listitem><para>Sets the CPU scheduling priority for executed
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processes. The available priority range depends on the
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selected CPU scheduling policy (see above). For real-time
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scheduling policies an integer between 1 (lowest priority) and
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99 (highest priority) can be used. See
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<citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for details. </para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>CPUSchedulingResetOnFork=</varname></term>
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<listitem><para>Takes a boolean argument. If true, elevated
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CPU scheduling priorities and policies will be reset when the
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executed processes fork, and can hence not leak into child
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processes. See
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<citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for details. Defaults to false.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>CPUAffinity=</varname></term>
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<listitem><para>Controls the CPU affinity of the executed
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processes. Takes a list of CPU indices or ranges separated by
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either whitespace or commas. CPU ranges are specified by the
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lower and upper CPU indices separated by a dash.
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This option may be specified more than once, in which case the
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specified CPU affinity masks are merged. If the empty string
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is assigned, the mask is reset, all assignments prior to this
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will have no effect. See
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<citerefentry><refentrytitle>sched_setaffinity</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for details.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>UMask=</varname></term>
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<listitem><para>Controls the file mode creation mask. Takes an
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access mode in octal notation. See
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<citerefentry><refentrytitle>umask</refentrytitle><manvolnum>2</manvolnum></citerefentry>
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for details. Defaults to 0022.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>Environment=</varname></term>
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<listitem><para>Sets environment variables for executed
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processes. Takes a space-separated list of variable
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assignments. This option may be specified more than once, in
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which case all listed variables will be set. If the same
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variable is set twice, the later setting will override the
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earlier setting. If the empty string is assigned to this
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option, the list of environment variables is reset, all prior
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assignments have no effect. Variable expansion is not
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performed inside the strings, however, specifier expansion is
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||
possible. The $ character has no special meaning. If you need
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||
to assign a value containing spaces to a variable, use double
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||
quotes (") for the assignment.</para>
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||
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||
<para>Example:
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||
<programlisting>Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"</programlisting>
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||
gives three variables <literal>VAR1</literal>,
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<literal>VAR2</literal>, <literal>VAR3</literal>
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||
with the values <literal>word1 word2</literal>,
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<literal>word3</literal>, <literal>$word 5 6</literal>.
|
||
</para>
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||
|
||
<para>
|
||
See
|
||
<citerefentry project='man-pages'><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>
|
||
for details about environment variables.</para></listitem>
|
||
</varlistentry>
|
||
<varlistentry>
|
||
<term><varname>EnvironmentFile=</varname></term>
|
||
<listitem><para>Similar to <varname>Environment=</varname> but
|
||
reads the environment variables from a text file. The text
|
||
file should contain new-line-separated variable assignments.
|
||
Empty lines, lines without an <literal>=</literal> separator,
|
||
or lines starting with ; or # will be ignored,
|
||
which may be used for commenting. A line ending with a
|
||
backslash will be concatenated with the following one,
|
||
allowing multiline variable definitions. The parser strips
|
||
leading and trailing whitespace from the values of
|
||
assignments, unless you use double quotes (").</para>
|
||
|
||
<para>The argument passed should be an absolute filename or
|
||
wildcard expression, optionally prefixed with
|
||
<literal>-</literal>, which indicates that if the file does
|
||
not exist, it will not be read and no error or warning message
|
||
is logged. This option may be specified more than once in
|
||
which case all specified files are read. If the empty string
|
||
is assigned to this option, the list of file to read is reset,
|
||
all prior assignments have no effect.</para>
|
||
|
||
<para>The files listed with this directive will be read
|
||
shortly before the process is executed (more specifically,
|
||
after all processes from a previous unit state terminated.
|
||
This means you can generate these files in one unit state, and
|
||
read it with this option in the next).</para>
|
||
|
||
<para>Settings from these
|
||
files override settings made with
|
||
<varname>Environment=</varname>. If the same variable is set
|
||
twice from these files, the files will be read in the order
|
||
they are specified and the later setting will override the
|
||
earlier setting.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>PassEnvironment=</varname></term>
|
||
|
||
<listitem><para>Pass environment variables from the systemd system
|
||
manager to executed processes. Takes a space-separated list of variable
|
||
names. This option may be specified more than once, in which case all
|
||
listed variables will be set. If the empty string is assigned to this
|
||
option, the list of environment variables is reset, all prior
|
||
assignments have no effect. Variables that are not set in the system
|
||
manager will not be passed and will be silently ignored.</para>
|
||
|
||
<para>Variables passed from this setting are overridden by those passed
|
||
from <varname>Environment=</varname> or
|
||
<varname>EnvironmentFile=</varname>.</para>
|
||
|
||
<para>Example:
|
||
<programlisting>PassEnvironment=VAR1 VAR2 VAR3</programlisting>
|
||
passes three variables <literal>VAR1</literal>,
|
||
<literal>VAR2</literal>, <literal>VAR3</literal>
|
||
with the values set for those variables in PID1.</para>
|
||
|
||
<para>
|
||
See
|
||
<citerefentry project='man-pages'><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>
|
||
for details about environment variables.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>StandardInput=</varname></term>
|
||
<listitem><para>Controls where file descriptor 0 (STDIN) of
|
||
the executed processes is connected to. Takes one of
|
||
<option>null</option>,
|
||
<option>tty</option>,
|
||
<option>tty-force</option>,
|
||
<option>tty-fail</option>,
|
||
<option>socket</option> or
|
||
<option>fd</option>.</para>
|
||
|
||
<para>If <option>null</option> is selected, standard input
|
||
will be connected to <filename>/dev/null</filename>, i.e. all
|
||
read attempts by the process will result in immediate
|
||
EOF.</para>
|
||
|
||
<para>If <option>tty</option> is selected, standard input is
|
||
connected to a TTY (as configured by
|
||
<varname>TTYPath=</varname>, see below) and the executed
|
||
process becomes the controlling process of the terminal. If
|
||
the terminal is already being controlled by another process,
|
||
the executed process waits until the current controlling
|
||
process releases the terminal.</para>
|
||
|
||
<para><option>tty-force</option> is similar to
|
||
<option>tty</option>, but the executed process is forcefully
|
||
and immediately made the controlling process of the terminal,
|
||
potentially removing previous controlling processes from the
|
||
terminal.</para>
|
||
|
||
<para><option>tty-fail</option> is similar to
|
||
<option>tty</option> but if the terminal already has a
|
||
controlling process start-up of the executed process
|
||
fails.</para>
|
||
|
||
<para>The <option>socket</option> option is only valid in
|
||
socket-activated services, and only when the socket
|
||
configuration file (see
|
||
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
||
for details) specifies a single socket only. If this option is
|
||
set, standard input will be connected to the socket the
|
||
service was activated from, which is primarily useful for
|
||
compatibility with daemons designed for use with the
|
||
traditional
|
||
<citerefentry project='freebsd'><refentrytitle>inetd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
||
daemon.</para>
|
||
|
||
<para>The <option>fd</option> option connects
|
||
the input stream to a single file descriptor provided by a socket unit.
|
||
A custom named file descriptor can be specified as part of this option,
|
||
after a <literal>:</literal> (e.g. <literal>fd:<replaceable>foobar</replaceable></literal>).
|
||
If no name is specified, <literal>stdin</literal> is assumed
|
||
(i.e. <literal>fd</literal> is equivalent to <literal>fd:stdin</literal>).
|
||
At least one socket unit defining such name must be explicitly provided via the
|
||
<varname>Sockets=</varname> option, and file descriptor name may differ
|
||
from the name of its containing socket unit.
|
||
If multiple matches are found, the first one will be used.
|
||
See <varname>FileDescriptorName=</varname> in
|
||
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
||
for more details about named descriptors and ordering.</para>
|
||
|
||
<para>This setting defaults to
|
||
<option>null</option>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>StandardOutput=</varname></term>
|
||
<listitem><para>Controls where file descriptor 1 (STDOUT) of
|
||
the executed processes is connected to. Takes one of
|
||
<option>inherit</option>,
|
||
<option>null</option>,
|
||
<option>tty</option>,
|
||
<option>journal</option>,
|
||
<option>syslog</option>,
|
||
<option>kmsg</option>,
|
||
<option>journal+console</option>,
|
||
<option>syslog+console</option>,
|
||
<option>kmsg+console</option>,
|
||
<option>socket</option> or
|
||
<option>fd</option>.</para>
|
||
|
||
<para><option>inherit</option> duplicates the file descriptor
|
||
of standard input for standard output.</para>
|
||
|
||
<para><option>null</option> connects standard output to
|
||
<filename>/dev/null</filename>, i.e. everything written to it
|
||
will be lost.</para>
|
||
|
||
<para><option>tty</option> connects standard output to a tty
|
||
(as configured via <varname>TTYPath=</varname>, see below). If
|
||
the TTY is used for output only, the executed process will not
|
||
become the controlling process of the terminal, and will not
|
||
fail or wait for other processes to release the
|
||
terminal.</para>
|
||
|
||
<para><option>journal</option> connects standard output with
|
||
the journal which is accessible via
|
||
<citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
|
||
Note that everything that is written to syslog or kmsg (see
|
||
below) is implicitly stored in the journal as well, the
|
||
specific two options listed below are hence supersets of this
|
||
one.</para>
|
||
|
||
<para><option>syslog</option> connects standard output to the
|
||
<citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
system syslog service, in addition to the journal. Note that
|
||
the journal daemon is usually configured to forward everything
|
||
it receives to syslog anyway, in which case this option is no
|
||
different from <option>journal</option>.</para>
|
||
|
||
<para><option>kmsg</option> connects standard output with the
|
||
kernel log buffer which is accessible via
|
||
<citerefentry project='man-pages'><refentrytitle>dmesg</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
||
in addition to the journal. The journal daemon might be
|
||
configured to send all logs to kmsg anyway, in which case this
|
||
option is no different from <option>journal</option>.</para>
|
||
|
||
<para><option>journal+console</option>,
|
||
<option>syslog+console</option> and
|
||
<option>kmsg+console</option> work in a similar way as the
|
||
three options above but copy the output to the system console
|
||
as well.</para>
|
||
|
||
<para><option>socket</option> connects standard output to a
|
||
socket acquired via socket activation. The semantics are
|
||
similar to the same option of
|
||
<varname>StandardInput=</varname>.</para>
|
||
|
||
<para>The <option>fd</option> option connects
|
||
the output stream to a single file descriptor provided by a socket unit.
|
||
A custom named file descriptor can be specified as part of this option,
|
||
after a <literal>:</literal> (e.g. <literal>fd:<replaceable>foobar</replaceable></literal>).
|
||
If no name is specified, <literal>stdout</literal> is assumed
|
||
(i.e. <literal>fd</literal> is equivalent to <literal>fd:stdout</literal>).
|
||
At least one socket unit defining such name must be explicitly provided via the
|
||
<varname>Sockets=</varname> option, and file descriptor name may differ
|
||
from the name of its containing socket unit.
|
||
If multiple matches are found, the first one will be used.
|
||
See <varname>FileDescriptorName=</varname> in
|
||
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
||
for more details about named descriptors and ordering.</para>
|
||
|
||
<para>If the standard output (or error output, see below) of a unit is connected to the journal, syslog or the
|
||
kernel log buffer, the unit will implicitly gain a dependency of type <varname>After=</varname> on
|
||
<filename>systemd-journald.socket</filename> (also see the automatic dependencies section above).</para>
|
||
|
||
<para>This setting defaults to the value set with
|
||
<option>DefaultStandardOutput=</option> in
|
||
<citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
||
which defaults to <option>journal</option>. Note that setting
|
||
this parameter might result in additional dependencies to be
|
||
added to the unit (see above).</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>StandardError=</varname></term>
|
||
<listitem><para>Controls where file descriptor 2 (STDERR) of
|
||
the executed processes is connected to. The available options
|
||
are identical to those of <varname>StandardOutput=</varname>,
|
||
with some exceptions: if set to <option>inherit</option> the
|
||
file descriptor used for standard output is duplicated for
|
||
standard error, while <option>fd</option> operates on the error
|
||
stream and will look by default for a descriptor named
|
||
<literal>stderr</literal>.</para>
|
||
|
||
<para>This setting defaults to the value set with
|
||
<option>DefaultStandardError=</option> in
|
||
<citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
||
which defaults to <option>inherit</option>. Note that setting
|
||
this parameter might result in additional dependencies to be
|
||
added to the unit (see above).</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>TTYPath=</varname></term>
|
||
<listitem><para>Sets the terminal device node to use if
|
||
standard input, output, or error are connected to a TTY (see
|
||
above). Defaults to
|
||
<filename>/dev/console</filename>.</para></listitem>
|
||
</varlistentry>
|
||
<varlistentry>
|
||
<term><varname>TTYReset=</varname></term>
|
||
<listitem><para>Reset the terminal device specified with
|
||
<varname>TTYPath=</varname> before and after execution.
|
||
Defaults to <literal>no</literal>.</para></listitem>
|
||
</varlistentry>
|
||
<varlistentry>
|
||
<term><varname>TTYVHangup=</varname></term>
|
||
<listitem><para>Disconnect all clients which have opened the
|
||
terminal device specified with <varname>TTYPath=</varname>
|
||
before and after execution. Defaults to
|
||
<literal>no</literal>.</para></listitem>
|
||
</varlistentry>
|
||
<varlistentry>
|
||
<term><varname>TTYVTDisallocate=</varname></term>
|
||
<listitem><para>If the terminal device specified with
|
||
<varname>TTYPath=</varname> is a virtual console terminal, try
|
||
to deallocate the TTY before and after execution. This ensures
|
||
that the screen and scrollback buffer is cleared. Defaults to
|
||
<literal>no</literal>.</para></listitem>
|
||
</varlistentry>
|
||
<varlistentry>
|
||
<term><varname>SyslogIdentifier=</varname></term>
|
||
<listitem><para>Sets the process name to prefix log lines sent
|
||
to the logging system or the kernel log buffer with. If not
|
||
set, defaults to the process name of the executed process.
|
||
This option is only useful when
|
||
<varname>StandardOutput=</varname> or
|
||
<varname>StandardError=</varname> are set to
|
||
<option>syslog</option>, <option>journal</option> or
|
||
<option>kmsg</option> (or to the same settings in combination
|
||
with <option>+console</option>).</para></listitem>
|
||
</varlistentry>
|
||
<varlistentry>
|
||
<term><varname>SyslogFacility=</varname></term>
|
||
<listitem><para>Sets the syslog facility to use when logging
|
||
to syslog. One of <option>kern</option>,
|
||
<option>user</option>, <option>mail</option>,
|
||
<option>daemon</option>, <option>auth</option>,
|
||
<option>syslog</option>, <option>lpr</option>,
|
||
<option>news</option>, <option>uucp</option>,
|
||
<option>cron</option>, <option>authpriv</option>,
|
||
<option>ftp</option>, <option>local0</option>,
|
||
<option>local1</option>, <option>local2</option>,
|
||
<option>local3</option>, <option>local4</option>,
|
||
<option>local5</option>, <option>local6</option> or
|
||
<option>local7</option>. See
|
||
<citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
for details. This option is only useful when
|
||
<varname>StandardOutput=</varname> or
|
||
<varname>StandardError=</varname> are set to
|
||
<option>syslog</option>. Defaults to
|
||
<option>daemon</option>.</para></listitem>
|
||
</varlistentry>
|
||
<varlistentry>
|
||
<term><varname>SyslogLevel=</varname></term>
|
||
<listitem><para>The default syslog level to use when logging to
|
||
syslog or the kernel log buffer. One of
|
||
<option>emerg</option>,
|
||
<option>alert</option>,
|
||
<option>crit</option>,
|
||
<option>err</option>,
|
||
<option>warning</option>,
|
||
<option>notice</option>,
|
||
<option>info</option>,
|
||
<option>debug</option>. See
|
||
<citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
for details. This option is only useful when
|
||
<varname>StandardOutput=</varname> or
|
||
<varname>StandardError=</varname> are set to
|
||
<option>syslog</option> or <option>kmsg</option>. Note that
|
||
individual lines output by the daemon might be prefixed with a
|
||
different log level which can be used to override the default
|
||
log level specified here. The interpretation of these prefixes
|
||
may be disabled with <varname>SyslogLevelPrefix=</varname>,
|
||
see below. For details, see
|
||
<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
||
|
||
Defaults to
|
||
<option>info</option>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>SyslogLevelPrefix=</varname></term>
|
||
<listitem><para>Takes a boolean argument. If true and
|
||
<varname>StandardOutput=</varname> or
|
||
<varname>StandardError=</varname> are set to
|
||
<option>syslog</option>, <option>kmsg</option> or
|
||
<option>journal</option>, log lines written by the executed
|
||
process that are prefixed with a log level will be passed on
|
||
to syslog with this log level set but the prefix removed. If
|
||
set to false, the interpretation of these prefixes is disabled
|
||
and the logged lines are passed on as-is. For details about
|
||
this prefixing see
|
||
<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
||
Defaults to true.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>TimerSlackNSec=</varname></term>
|
||
<listitem><para>Sets the timer slack in nanoseconds for the
|
||
executed processes. The timer slack controls the accuracy of
|
||
wake-ups triggered by timers. See
|
||
<citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
|
||
for more information. Note that in contrast to most other time
|
||
span definitions this parameter takes an integer value in
|
||
nano-seconds if no unit is specified. The usual time units are
|
||
understood too.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>LimitCPU=</varname></term>
|
||
<term><varname>LimitFSIZE=</varname></term>
|
||
<term><varname>LimitDATA=</varname></term>
|
||
<term><varname>LimitSTACK=</varname></term>
|
||
<term><varname>LimitCORE=</varname></term>
|
||
<term><varname>LimitRSS=</varname></term>
|
||
<term><varname>LimitNOFILE=</varname></term>
|
||
<term><varname>LimitAS=</varname></term>
|
||
<term><varname>LimitNPROC=</varname></term>
|
||
<term><varname>LimitMEMLOCK=</varname></term>
|
||
<term><varname>LimitLOCKS=</varname></term>
|
||
<term><varname>LimitSIGPENDING=</varname></term>
|
||
<term><varname>LimitMSGQUEUE=</varname></term>
|
||
<term><varname>LimitNICE=</varname></term>
|
||
<term><varname>LimitRTPRIO=</varname></term>
|
||
<term><varname>LimitRTTIME=</varname></term>
|
||
<listitem><para>Set soft and hard limits on various resources for executed processes. See
|
||
<citerefentry><refentrytitle>setrlimit</refentrytitle><manvolnum>2</manvolnum></citerefentry> for details on
|
||
the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
|
||
specific soft and hard limit to the same value, or as colon-separated pair <option>soft:hard</option> to set
|
||
both limits individually (e.g. <literal>LimitAS=4G:16G</literal>). Use the string <varname>infinity</varname>
|
||
to configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base
|
||
1024) may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time
|
||
values, the usual time units ms, s, min, h and so on may be used (see
|
||
<citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
|
||
details). Note that if no time unit is specified for <varname>LimitCPU=</varname> the default unit of seconds
|
||
is implied, while for <varname>LimitRTTIME=</varname> the default unit of microseconds is implied. Also, note
|
||
that the effective granularity of the limits might influence their enforcement. For example, time limits
|
||
specified for <varname>LimitCPU=</varname> will be rounded up implicitly to multiples of 1s. For
|
||
<varname>LimitNICE=</varname> the value may be specified in two syntaxes: if prefixed with <literal>+</literal>
|
||
or <literal>-</literal>, the value is understood as regular Linux nice value in the range -20..19. If not
|
||
prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
|
||
equivalent to 1).</para>
|
||
|
||
<para>Note that most process resource limits configured with
|
||
these options are per-process, and processes may fork in order
|
||
to acquire a new set of resources that are accounted
|
||
independently of the original process, and may thus escape
|
||
limits set. Also note that <varname>LimitRSS=</varname> is not
|
||
implemented on Linux, and setting it has no effect. Often it
|
||
is advisable to prefer the resource controls listed in
|
||
<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
||
over these per-process limits, as they apply to services as a
|
||
whole, may be altered dynamically at runtime, and are
|
||
generally more expressive. For example,
|
||
<varname>MemoryLimit=</varname> is a more powerful (and
|
||
working) replacement for <varname>LimitRSS=</varname>.</para>
|
||
|
||
<para>For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
|
||
per-user instance of
|
||
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>), these limits are
|
||
bound by (possibly more restrictive) per-user limits enforced by the OS.</para>
|
||
|
||
<para>Resource limits not configured explicitly for a unit default to the value configured in the various
|
||
<varname>DefaultLimitCPU=</varname>, <varname>DefaultLimitFSIZE=</varname>, … options available in
|
||
<citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, and –
|
||
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
|
||
services, see above).</para>
|
||
|
||
<table>
|
||
<title>Resource limit directives, their equivalent <command>ulimit</command> shell commands and the unit used</title>
|
||
|
||
<tgroup cols='3'>
|
||
<colspec colname='directive' />
|
||
<colspec colname='equivalent' />
|
||
<colspec colname='unit' />
|
||
<thead>
|
||
<row>
|
||
<entry>Directive</entry>
|
||
<entry><command>ulimit</command> equivalent</entry>
|
||
<entry>Unit</entry>
|
||
</row>
|
||
</thead>
|
||
<tbody>
|
||
<row>
|
||
<entry>LimitCPU=</entry>
|
||
<entry>ulimit -t</entry>
|
||
<entry>Seconds</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitFSIZE=</entry>
|
||
<entry>ulimit -f</entry>
|
||
<entry>Bytes</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitDATA=</entry>
|
||
<entry>ulimit -d</entry>
|
||
<entry>Bytes</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitSTACK=</entry>
|
||
<entry>ulimit -s</entry>
|
||
<entry>Bytes</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitCORE=</entry>
|
||
<entry>ulimit -c</entry>
|
||
<entry>Bytes</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitRSS=</entry>
|
||
<entry>ulimit -m</entry>
|
||
<entry>Bytes</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitNOFILE=</entry>
|
||
<entry>ulimit -n</entry>
|
||
<entry>Number of File Descriptors</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitAS=</entry>
|
||
<entry>ulimit -v</entry>
|
||
<entry>Bytes</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitNPROC=</entry>
|
||
<entry>ulimit -u</entry>
|
||
<entry>Number of Processes</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitMEMLOCK=</entry>
|
||
<entry>ulimit -l</entry>
|
||
<entry>Bytes</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitLOCKS=</entry>
|
||
<entry>ulimit -x</entry>
|
||
<entry>Number of Locks</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitSIGPENDING=</entry>
|
||
<entry>ulimit -i</entry>
|
||
<entry>Number of Queued Signals</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitMSGQUEUE=</entry>
|
||
<entry>ulimit -q</entry>
|
||
<entry>Bytes</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitNICE=</entry>
|
||
<entry>ulimit -e</entry>
|
||
<entry>Nice Level</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitRTPRIO=</entry>
|
||
<entry>ulimit -r</entry>
|
||
<entry>Realtime Priority</entry>
|
||
</row>
|
||
<row>
|
||
<entry>LimitRTTIME=</entry>
|
||
<entry>No equivalent</entry>
|
||
<entry>Microseconds</entry>
|
||
</row>
|
||
</tbody>
|
||
</tgroup>
|
||
</table></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>PAMName=</varname></term>
|
||
<listitem><para>Sets the PAM service name to set up a session
|
||
as. If set, the executed process will be registered as a PAM
|
||
session under the specified service name. This is only useful
|
||
in conjunction with the <varname>User=</varname> setting. If
|
||
not set, no PAM session will be opened for the executed
|
||
processes. See
|
||
<citerefentry project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
||
for details.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>CapabilityBoundingSet=</varname></term>
|
||
|
||
<listitem><para>Controls which capabilities to include in the capability bounding set for the executed
|
||
process. See <citerefentry
|
||
project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
|
||
details. Takes a whitespace-separated list of capability names, e.g. <constant>CAP_SYS_ADMIN</constant>,
|
||
<constant>CAP_DAC_OVERRIDE</constant>, <constant>CAP_SYS_PTRACE</constant>. Capabilities listed will be
|
||
included in the bounding set, all others are removed. If the list of capabilities is prefixed with
|
||
<literal>~</literal>, all but the listed capabilities will be included, the effect of the assignment
|
||
inverted. Note that this option also affects the respective capabilities in the effective, permitted and
|
||
inheritable capability sets. If this option is not used, the capability bounding set is not modified on process
|
||
execution, hence no limits on the capabilities of the process are enforced. This option may appear more than
|
||
once, in which case the bounding sets are merged. If the empty string is assigned to this option, the bounding
|
||
set is reset to the empty capability set, and all prior settings have no effect. If set to
|
||
<literal>~</literal> (without any further argument), the bounding set is reset to the full set of available
|
||
capabilities, also undoing any previous settings. This does not affect commands prefixed with
|
||
<literal>+</literal>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>AmbientCapabilities=</varname></term>
|
||
|
||
<listitem><para>Controls which capabilities to include in the ambient capability set for the executed
|
||
process. Takes a whitespace-separated list of capability names, e.g. <constant>CAP_SYS_ADMIN</constant>,
|
||
<constant>CAP_DAC_OVERRIDE</constant>, <constant>CAP_SYS_PTRACE</constant>. This option may appear more than
|
||
once in which case the ambient capability sets are merged. If the list of capabilities is prefixed with
|
||
<literal>~</literal>, all but the listed capabilities will be included, the effect of the assignment
|
||
inverted. If the empty string is assigned to this option, the ambient capability set is reset to the empty
|
||
capability set, and all prior settings have no effect. If set to <literal>~</literal> (without any further
|
||
argument), the ambient capability set is reset to the full set of available capabilities, also undoing any
|
||
previous settings. Note that adding capabilities to ambient capability set adds them to the process's inherited
|
||
capability set. </para><para> Ambient capability sets are useful if you want to execute a process as a
|
||
non-privileged user but still want to give it some capabilities. Note that in this case option
|
||
<constant>keep-caps</constant> is automatically added to <varname>SecureBits=</varname> to retain the
|
||
capabilities over the user change. <varname>AmbientCapabilities=</varname> does not affect commands prefixed
|
||
with <literal>+</literal>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>SecureBits=</varname></term>
|
||
<listitem><para>Controls the secure bits set for the executed
|
||
process. Takes a space-separated combination of options from
|
||
the following list:
|
||
<option>keep-caps</option>,
|
||
<option>keep-caps-locked</option>,
|
||
<option>no-setuid-fixup</option>,
|
||
<option>no-setuid-fixup-locked</option>,
|
||
<option>noroot</option>, and
|
||
<option>noroot-locked</option>.
|
||
This option may appear more than once, in which case the secure
|
||
bits are ORed. If the empty string is assigned to this option,
|
||
the bits are reset to 0. This does not affect commands prefixed with <literal>+</literal>.
|
||
See <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
|
||
for details.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>ReadWritePaths=</varname></term>
|
||
<term><varname>ReadOnlyPaths=</varname></term>
|
||
<term><varname>InaccessiblePaths=</varname></term>
|
||
|
||
<listitem><para>Sets up a new file system namespace for executed processes. These options may be used to limit
|
||
access a process might have to the file system hierarchy. Each setting takes a space-separated list of paths
|
||
relative to the host's root directory (i.e. the system running the service manager). Note that if paths
|
||
contain symlinks, they are resolved relative to the root directory set with
|
||
<varname>RootDirectory=</varname>.</para>
|
||
|
||
<para>Paths listed in <varname>ReadWritePaths=</varname> are accessible from within the namespace with the same
|
||
access modes as from outside of it. Paths listed in <varname>ReadOnlyPaths=</varname> are accessible for
|
||
reading only, writing will be refused even if the usual file access controls would permit this. Nest
|
||
<varname>ReadWritePaths=</varname> inside of <varname>ReadOnlyPaths=</varname> in order to provide writable
|
||
subdirectories within read-only directories. Use <varname>ReadWritePaths=</varname> in order to whitelist
|
||
specific paths for write access if <varname>ProtectSystem=strict</varname> is used. Paths listed in
|
||
<varname>InaccessiblePaths=</varname> will be made inaccessible for processes inside the namespace (along with
|
||
everything below them in the file system hierarchy).</para>
|
||
|
||
<para>Note that restricting access with these options does not extend to submounts of a directory that are
|
||
created later on. Non-directory paths may be specified as well. These options may be specified more than once,
|
||
in which case all paths listed will have limited access from within the namespace. If the empty string is
|
||
assigned to this option, the specific list is reset, and all prior assignments have no effect.</para>
|
||
|
||
<para>Paths in <varname>ReadWritePaths=</varname>, <varname>ReadOnlyPaths=</varname> and
|
||
<varname>InaccessiblePaths=</varname> may be prefixed with <literal>-</literal>, in which case they will be
|
||
ignored when they do not exist. If prefixed with <literal>+</literal> the paths are taken relative to the root
|
||
directory of the unit, as configured with <varname>RootDirectory=</varname>, instead of relative to the root
|
||
directory of the host (see above). When combining <literal>-</literal> and <literal>+</literal> on the same
|
||
path make sure to specify <literal>-</literal> first, and <literal>+</literal> second.</para>
|
||
|
||
<para>Note that using this setting will disconnect propagation of mounts from the service to the host
|
||
(propagation in the opposite direction continues to work). This means that this setting may not be used for
|
||
services which shall be able to install mount points in the main mount namespace. Note that the effect of these
|
||
settings may be undone by privileged processes. In order to set up an effective sandboxed environment for a
|
||
unit it is thus recommended to combine these settings with either
|
||
<varname>CapabilityBoundingSet=~CAP_SYS_ADMIN</varname> or
|
||
<varname>SystemCallFilter=~@mount</varname>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>BindPaths=</varname></term>
|
||
<term><varname>BindReadOnlyPaths=</varname></term>
|
||
|
||
<listitem><para>Configures unit-specific bind mounts. A bind mount makes a particular file or directory
|
||
available at an additional place in the unit's view of the file system. Any bind mounts created with this
|
||
option are specific to the unit, and are not visible in the host's mount table. This option expects a
|
||
whitespace separated list of bind mount definitions. Each definition consists of a colon-separated triple of
|
||
source path, destination path and option string, where the latter two are optional. If only a source path is
|
||
specified the source and destination is taken to be the same. The option string may be either
|
||
<literal>rbind</literal> or <literal>norbind</literal> for configuring a recursive or non-recursive bind
|
||
mount. If the destination parth is omitted, the option string must be omitted too.</para>
|
||
|
||
<para><varname>BindPaths=</varname> creates regular writable bind mounts (unless the source file system mount
|
||
is already marked read-only), while <varname>BindReadOnlyPaths=</varname> creates read-only bind mounts. These
|
||
settings may be used more than once, each usage appends to the unit's list of bind mounts. If the empty string
|
||
is assigned to either of these two options the entire list of bind mounts defined prior to this is reset. Note
|
||
that in this case both read-only and regular bind mounts are reset, regardless which of the two settings is
|
||
used.</para>
|
||
|
||
<para>This option is particularly useful when <varname>RootDirectory=</varname> is used. In this case the
|
||
source path refers to a path on the host file system, while the destination path referes to a path below the
|
||
root directory of the unit.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>PrivateTmp=</varname></term>
|
||
|
||
<listitem><para>Takes a boolean argument. If true, sets up a new file system namespace for the executed
|
||
processes and mounts private <filename>/tmp</filename> and <filename>/var/tmp</filename> directories inside it
|
||
that is not shared by processes outside of the namespace. This is useful to secure access to temporary files of
|
||
the process, but makes sharing between processes via <filename>/tmp</filename> or <filename>/var/tmp</filename>
|
||
impossible. If this is enabled, all temporary files created by a service in these directories will be removed
|
||
after the service is stopped. Defaults to false. It is possible to run two or more units within the same
|
||
private <filename>/tmp</filename> and <filename>/var/tmp</filename> namespace by using the
|
||
<varname>JoinsNamespaceOf=</varname> directive, see
|
||
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
|
||
details. This setting is implied if <varname>DynamicUser=</varname> is set. For this setting the same
|
||
restrictions regarding mount propagation and privileges apply as for <varname>ReadOnlyPaths=</varname> and
|
||
related calls, see above.</para></listitem>
|
||
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>PrivateDevices=</varname></term>
|
||
|
||
<listitem><para>Takes a boolean argument. If true, sets up a new /dev namespace for the executed processes and
|
||
only adds API pseudo devices such as <filename>/dev/null</filename>, <filename>/dev/zero</filename> or
|
||
<filename>/dev/random</filename> (as well as the pseudo TTY subsystem) to it, but no physical devices such as
|
||
<filename>/dev/sda</filename>, system memory <filename>/dev/mem</filename>, system ports
|
||
<filename>/dev/port</filename> and others. This is useful to securely turn off physical device access by the
|
||
executed process. Defaults to false. Enabling this option will install a system call filter to block low-level
|
||
I/O system calls that are grouped in the <varname>@raw-io</varname> set, will also remove
|
||
<constant>CAP_MKNOD</constant> and <constant>CAP_SYS_RAWIO</constant> from the capability bounding set for
|
||
the unit (see above), and set <varname>DevicePolicy=closed</varname> (see
|
||
<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
||
for details). Note that using this setting will disconnect propagation of mounts from the service to the host
|
||
(propagation in the opposite direction continues to work). This means that this setting may not be used for
|
||
services which shall be able to install mount points in the main mount namespace. The /dev namespace will be
|
||
mounted read-only and 'noexec'. The latter may break old programs which try to set up executable memory by
|
||
using <citerefentry><refentrytitle>mmap</refentrytitle><manvolnum>2</manvolnum></citerefentry> of
|
||
<filename>/dev/zero</filename> instead of using <constant>MAP_ANON</constant>. This setting is implied if
|
||
<varname>DynamicUser=</varname> is set. For this setting the same restrictions regarding mount propagation and
|
||
privileges apply as for <varname>ReadOnlyPaths=</varname> and related calls, see above.
|
||
If turned on and if running in user mode, or in system mode, but without the <constant>CAP_SYS_ADMIN</constant>
|
||
capability (e.g. setting <varname>User=</varname>), <varname>NoNewPrivileges=yes</varname>
|
||
is implied.
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>PrivateNetwork=</varname></term>
|
||
|
||
<listitem><para>Takes a boolean argument. If true, sets up a
|
||
new network namespace for the executed processes and
|
||
configures only the loopback network device
|
||
<literal>lo</literal> inside it. No other network devices will
|
||
be available to the executed process. This is useful to
|
||
securely turn off network access by the executed process.
|
||
Defaults to false. It is possible to run two or more units
|
||
within the same private network namespace by using the
|
||
<varname>JoinsNamespaceOf=</varname> directive, see
|
||
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
||
for details. Note that this option will disconnect all socket
|
||
families from the host, this includes AF_NETLINK and AF_UNIX.
|
||
The latter has the effect that AF_UNIX sockets in the abstract
|
||
socket namespace will become unavailable to the processes
|
||
(however, those located in the file system will continue to be
|
||
accessible).</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>PrivateUsers=</varname></term>
|
||
|
||
<listitem><para>Takes a boolean argument. If true, sets up a new user namespace for the executed processes and
|
||
configures a minimal user and group mapping, that maps the <literal>root</literal> user and group as well as
|
||
the unit's own user and group to themselves and everything else to the <literal>nobody</literal> user and
|
||
group. This is useful to securely detach the user and group databases used by the unit from the rest of the
|
||
system, and thus to create an effective sandbox environment. All files, directories, processes, IPC objects and
|
||
other resources owned by users/groups not equaling <literal>root</literal> or the unit's own will stay visible
|
||
from within the unit but appear owned by the <literal>nobody</literal> user and group. If this mode is enabled,
|
||
all unit processes are run without privileges in the host user namespace (regardless if the unit's own
|
||
user/group is <literal>root</literal> or not). Specifically this means that the process will have zero process
|
||
capabilities on the host's user namespace, but full capabilities within the service's user namespace. Settings
|
||
such as <varname>CapabilityBoundingSet=</varname> will affect only the latter, and there's no way to acquire
|
||
additional capabilities in the host's user namespace. Defaults to off.</para>
|
||
|
||
<para>This setting is particularly useful in conjunction with <varname>RootDirectory=</varname>, as the need to
|
||
synchronize the user and group databases in the root directory and on the host is reduced, as the only users
|
||
and groups who need to be matched are <literal>root</literal>, <literal>nobody</literal> and the unit's own
|
||
user and group.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>ProtectSystem=</varname></term>
|
||
|
||
<listitem><para>Takes a boolean argument or the special values <literal>full</literal> or
|
||
<literal>strict</literal>. If true, mounts the <filename>/usr</filename> and <filename>/boot</filename>
|
||
directories read-only for processes invoked by this unit. If set to <literal>full</literal>, the
|
||
<filename>/etc</filename> directory is mounted read-only, too. If set to <literal>strict</literal> the entire
|
||
file system hierarchy is mounted read-only, except for the API file system subtrees <filename>/dev</filename>,
|
||
<filename>/proc</filename> and <filename>/sys</filename> (protect these directories using
|
||
<varname>PrivateDevices=</varname>, <varname>ProtectKernelTunables=</varname>,
|
||
<varname>ProtectControlGroups=</varname>). This setting ensures that any modification of the vendor-supplied
|
||
operating system (and optionally its configuration, and local mounts) is prohibited for the service. It is
|
||
recommended to enable this setting for all long-running services, unless they are involved with system updates
|
||
or need to modify the operating system in other ways. If this option is used,
|
||
<varname>ReadWritePaths=</varname> may be used to exclude specific directories from being made read-only. This
|
||
setting is implied if <varname>DynamicUser=</varname> is set. For this setting the same restrictions regarding
|
||
mount propagation and privileges apply as for <varname>ReadOnlyPaths=</varname> and related calls, see
|
||
above. Defaults to off.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>ProtectHome=</varname></term>
|
||
|
||
<listitem><para>Takes a boolean argument or <literal>read-only</literal>. If true, the directories
|
||
<filename>/home</filename>, <filename>/root</filename> and <filename>/run/user</filename> are made inaccessible
|
||
and empty for processes invoked by this unit. If set to <literal>read-only</literal>, the three directories are
|
||
made read-only instead. It is recommended to enable this setting for all long-running services (in particular
|
||
network-facing ones), to ensure they cannot get access to private user data, unless the services actually
|
||
require access to the user's private data. This setting is implied if <varname>DynamicUser=</varname> is
|
||
set. For this setting the same restrictions regarding mount propagation and privileges apply as for
|
||
<varname>ReadOnlyPaths=</varname> and related calls, see above.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>ProtectKernelTunables=</varname></term>
|
||
|
||
<listitem><para>Takes a boolean argument. If true, kernel variables accessible through
|
||
<filename>/proc/sys</filename>, <filename>/sys</filename>, <filename>/proc/sysrq-trigger</filename>,
|
||
<filename>/proc/latency_stats</filename>, <filename>/proc/acpi</filename>,
|
||
<filename>/proc/timer_stats</filename>, <filename>/proc/fs</filename> and <filename>/proc/irq</filename> will
|
||
be made read-only to all processes of the unit. Usually, tunable kernel variables should only be written at
|
||
boot-time, with the <citerefentry><refentrytitle>sysctl.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
||
mechanism. Almost no services need to write to these at runtime; it is hence recommended to turn this on for
|
||
most services. For this setting the same restrictions regarding mount propagation and privileges apply as for
|
||
<varname>ReadOnlyPaths=</varname> and related calls, see above. Defaults to off.
|
||
If turned on and if running in user mode, or in system mode, but without the <constant>CAP_SYS_ADMIN</constant>
|
||
capability (e.g. setting <varname>User=</varname>), <varname>NoNewPrivileges=yes</varname>
|
||
is implied. Note that this option does not prevent kernel tuning through IPC interfaces
|
||
and external programs. However <varname>InaccessiblePaths=</varname> can be used to
|
||
make some IPC file system objects inaccessible.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>ProtectKernelModules=</varname></term>
|
||
|
||
<listitem><para>Takes a boolean argument. If true, explicit module loading will
|
||
be denied. This allows to turn off module load and unload operations on modular
|
||
kernels. It is recommended to turn this on for most services that do not need special
|
||
file systems or extra kernel modules to work. Default to off. Enabling this option
|
||
removes <constant>CAP_SYS_MODULE</constant> from the capability bounding set for
|
||
the unit, and installs a system call filter to block module system calls,
|
||
also <filename>/usr/lib/modules</filename> is made inaccessible. For this
|
||
setting the same restrictions regarding mount propagation and privileges
|
||
apply as for <varname>ReadOnlyPaths=</varname> and related calls, see above.
|
||
Note that limited automatic module loading due to user configuration or kernel
|
||
mapping tables might still happen as side effect of requested user operations,
|
||
both privileged and unprivileged. To disable module auto-load feature please see
|
||
<citerefentry><refentrytitle>sysctl.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
||
<constant>kernel.modules_disabled</constant> mechanism and
|
||
<filename>/proc/sys/kernel/modules_disabled</filename> documentation.
|
||
If turned on and if running in user mode, or in system mode, but without the <constant>CAP_SYS_ADMIN</constant>
|
||
capability (e.g. setting <varname>User=</varname>), <varname>NoNewPrivileges=yes</varname>
|
||
is implied.
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>ProtectControlGroups=</varname></term>
|
||
|
||
<listitem><para>Takes a boolean argument. If true, the Linux Control Groups (<citerefentry
|
||
project='man-pages'><refentrytitle>cgroups</refentrytitle><manvolnum>7</manvolnum></citerefentry>) hierarchies
|
||
accessible through <filename>/sys/fs/cgroup</filename> will be made read-only to all processes of the
|
||
unit. Except for container managers no services should require write access to the control groups hierarchies;
|
||
it is hence recommended to turn this on for most services. For this setting the same restrictions regarding
|
||
mount propagation and privileges apply as for <varname>ReadOnlyPaths=</varname> and related calls, see
|
||
above. Defaults to off.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>MountFlags=</varname></term>
|
||
|
||
<listitem><para>Takes a mount propagation flag: <option>shared</option>, <option>slave</option> or
|
||
<option>private</option>, which control whether mounts in the file system namespace set up for this unit's
|
||
processes will receive or propagate mounts or unmounts. See <citerefentry
|
||
project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>2</manvolnum></citerefentry> for
|
||
details. Defaults to <option>shared</option>. Use <option>shared</option> to ensure that mounts and unmounts
|
||
are propagated from the host to the container and vice versa. Use <option>slave</option> to run processes so
|
||
that none of their mounts and unmounts will propagate to the host. Use <option>private</option> to also ensure
|
||
that no mounts and unmounts from the host will propagate into the unit processes' namespace. Note that
|
||
<option>slave</option> means that file systems mounted on the host might stay mounted continuously in the
|
||
unit's namespace, and thus keep the device busy. Note that the file system namespace related options
|
||
(<varname>PrivateTmp=</varname>, <varname>PrivateDevices=</varname>, <varname>ProtectSystem=</varname>,
|
||
<varname>ProtectHome=</varname>, <varname>ProtectKernelTunables=</varname>,
|
||
<varname>ProtectControlGroups=</varname>, <varname>ReadOnlyPaths=</varname>,
|
||
<varname>InaccessiblePaths=</varname>, <varname>ReadWritePaths=</varname>) require that mount and unmount
|
||
propagation from the unit's file system namespace is disabled, and hence downgrade <option>shared</option> to
|
||
<option>slave</option>. </para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>UtmpIdentifier=</varname></term>
|
||
|
||
<listitem><para>Takes a four character identifier string for
|
||
an <citerefentry
|
||
project='man-pages'><refentrytitle>utmp</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
||
and wtmp entry for this service. This should only be
|
||
set for services such as <command>getty</command>
|
||
implementations (such as <citerefentry
|
||
project='die-net'><refentrytitle>agetty</refentrytitle><manvolnum>8</manvolnum></citerefentry>)
|
||
where utmp/wtmp entries must be created and cleared before and
|
||
after execution, or for services that shall be executed as if
|
||
they were run by a <command>getty</command> process (see
|
||
below). If the configured string is longer than four
|
||
characters, it is truncated and the terminal four characters
|
||
are used. This setting interprets %I style string
|
||
replacements. This setting is unset by default, i.e. no
|
||
utmp/wtmp entries are created or cleaned up for this
|
||
service.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>UtmpMode=</varname></term>
|
||
|
||
<listitem><para>Takes one of <literal>init</literal>,
|
||
<literal>login</literal> or <literal>user</literal>. If
|
||
<varname>UtmpIdentifier=</varname> is set, controls which
|
||
type of <citerefentry
|
||
project='man-pages'><refentrytitle>utmp</refentrytitle><manvolnum>5</manvolnum></citerefentry>/wtmp
|
||
entries for this service are generated. This setting has no
|
||
effect unless <varname>UtmpIdentifier=</varname> is set
|
||
too. If <literal>init</literal> is set, only an
|
||
<constant>INIT_PROCESS</constant> entry is generated and the
|
||
invoked process must implement a
|
||
<command>getty</command>-compatible utmp/wtmp logic. If
|
||
<literal>login</literal> is set, first an
|
||
<constant>INIT_PROCESS</constant> entry, followed by a
|
||
<constant>LOGIN_PROCESS</constant> entry is generated. In
|
||
this case, the invoked process must implement a <citerefentry
|
||
project='die-net'><refentrytitle>login</refentrytitle><manvolnum>1</manvolnum></citerefentry>-compatible
|
||
utmp/wtmp logic. If <literal>user</literal> is set, first an
|
||
<constant>INIT_PROCESS</constant> entry, then a
|
||
<constant>LOGIN_PROCESS</constant> entry and finally a
|
||
<constant>USER_PROCESS</constant> entry is generated. In this
|
||
case, the invoked process may be any process that is suitable
|
||
to be run as session leader. Defaults to
|
||
<literal>init</literal>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>SELinuxContext=</varname></term>
|
||
|
||
<listitem><para>Set the SELinux security context of the
|
||
executed process. If set, this will override the automated
|
||
domain transition. However, the policy still needs to
|
||
authorize the transition. This directive is ignored if SELinux
|
||
is disabled. If prefixed by <literal>-</literal>, all errors
|
||
will be ignored. This does not affect commands prefixed with <literal>+</literal>.
|
||
See <citerefentry project='die-net'><refentrytitle>setexeccon</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
for details.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>AppArmorProfile=</varname></term>
|
||
|
||
<listitem><para>Takes a profile name as argument. The process
|
||
executed by the unit will switch to this profile when started.
|
||
Profiles must already be loaded in the kernel, or the unit
|
||
will fail. This result in a non operation if AppArmor is not
|
||
enabled. If prefixed by <literal>-</literal>, all errors will
|
||
be ignored. This does not affect commands prefixed with <literal>+</literal>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>SmackProcessLabel=</varname></term>
|
||
|
||
<listitem><para>Takes a <option>SMACK64</option> security
|
||
label as argument. The process executed by the unit will be
|
||
started under this label and SMACK will decide whether the
|
||
process is allowed to run or not, based on it. The process
|
||
will continue to run under the label specified here unless the
|
||
executable has its own <option>SMACK64EXEC</option> label, in
|
||
which case the process will transition to run under that
|
||
label. When not specified, the label that systemd is running
|
||
under is used. This directive is ignored if SMACK is
|
||
disabled.</para>
|
||
|
||
<para>The value may be prefixed by <literal>-</literal>, in
|
||
which case all errors will be ignored. An empty value may be
|
||
specified to unset previous assignments. This does not affect
|
||
commands prefixed with <literal>+</literal>.</para>
|
||
</listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>IgnoreSIGPIPE=</varname></term>
|
||
|
||
<listitem><para>Takes a boolean argument. If true, causes
|
||
<constant>SIGPIPE</constant> to be ignored in the executed
|
||
process. Defaults to true because <constant>SIGPIPE</constant>
|
||
generally is useful only in shell pipelines.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>NoNewPrivileges=</varname></term>
|
||
|
||
<listitem><para>Takes a boolean argument. If true, ensures that the service process and all its children can
|
||
never gain new privileges through <function>execve()</function> (e.g. via setuid or setgid bits, or filesystem
|
||
capabilities). This is the simplest and most effective way to ensure that a process and its children can never
|
||
elevate privileges again. Defaults to false, but certain settings force
|
||
<varname>NoNewPrivileges=yes</varname>, ignoring the value of this setting. This is the case when
|
||
<varname>SystemCallFilter=</varname>, <varname>SystemCallArchitectures=</varname>,
|
||
<varname>RestrictAddressFamilies=</varname>, <varname>RestrictNamespaces=</varname>,
|
||
<varname>PrivateDevices=</varname>, <varname>ProtectKernelTunables=</varname>,
|
||
<varname>ProtectKernelModules=</varname>, <varname>MemoryDenyWriteExecute=</varname>, or
|
||
<varname>RestrictRealtime=</varname> are specified.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>SystemCallFilter=</varname></term>
|
||
|
||
<listitem><para>Takes a space-separated list of system call names. If this setting is used, all system calls
|
||
executed by the unit processes except for the listed ones will result in immediate process termination with the
|
||
<constant>SIGSYS</constant> signal (whitelisting). If the first character of the list is <literal>~</literal>,
|
||
the effect is inverted: only the listed system calls will result in immediate process termination
|
||
(blacklisting). If running in user mode, or in system mode, but without the <constant>CAP_SYS_ADMIN</constant>
|
||
capability (e.g. setting <varname>User=nobody</varname>), <varname>NoNewPrivileges=yes</varname> is
|
||
implied. This feature makes use of the Secure Computing Mode 2 interfaces of the kernel ('seccomp filtering')
|
||
and is useful for enforcing a minimal sandboxing environment. Note that the <function>execve</function>,
|
||
<function>exit</function>, <function>exit_group</function>, <function>getrlimit</function>,
|
||
<function>rt_sigreturn</function>, <function>sigreturn</function> system calls and the system calls for
|
||
querying time and sleeping are implicitly whitelisted and do not need to be listed explicitly. This option may
|
||
be specified more than once, in which case the filter masks are merged. If the empty string is assigned, the
|
||
filter is reset, all prior assignments will have no effect. This does not affect commands prefixed with
|
||
<literal>+</literal>.</para>
|
||
|
||
<para>Note that strict system call filters may impact execution and error handling code paths of the service
|
||
invocation. Specifically, access to the <function>execve</function> system call is required for the execution
|
||
of the service binary — if it is blocked service invocation will necessarily fail. Also, if execution of the
|
||
service binary fails for some reason (for example: missing service executable), the error handling logic might
|
||
require access to an additional set of system calls in order to process and log this failure correctly. It
|
||
might be necessary to temporarily disable system call filters in order to simplify debugging of such
|
||
failures.</para>
|
||
|
||
<para>If you specify both types of this option (i.e.
|
||
whitelisting and blacklisting), the first encountered will
|
||
take precedence and will dictate the default action
|
||
(termination or approval of a system call). Then the next
|
||
occurrences of this option will add or delete the listed
|
||
system calls from the set of the filtered system calls,
|
||
depending of its type and the default action. (For example, if
|
||
you have started with a whitelisting of
|
||
<function>read</function> and <function>write</function>, and
|
||
right after it add a blacklisting of
|
||
<function>write</function>, then <function>write</function>
|
||
will be removed from the set.)</para>
|
||
|
||
<para>As the number of possible system
|
||
calls is large, predefined sets of system calls are provided.
|
||
A set starts with <literal>@</literal> character, followed by
|
||
name of the set.
|
||
|
||
<table>
|
||
<title>Currently predefined system call sets</title>
|
||
|
||
<tgroup cols='2'>
|
||
<colspec colname='set' />
|
||
<colspec colname='description' />
|
||
<thead>
|
||
<row>
|
||
<entry>Set</entry>
|
||
<entry>Description</entry>
|
||
</row>
|
||
</thead>
|
||
<tbody>
|
||
<row>
|
||
<entry>@basic-io</entry>
|
||
<entry>System calls for basic I/O: reading, writing, seeking, file descriptor duplication and closing (<citerefentry project='man-pages'><refentrytitle>read</refentrytitle><manvolnum>2</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>write</refentrytitle><manvolnum>2</manvolnum></citerefentry>, and related calls)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>@clock</entry>
|
||
<entry>System calls for changing the system clock (<citerefentry project='man-pages'><refentrytitle>adjtimex</refentrytitle><manvolnum>2</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>settimeofday</refentrytitle><manvolnum>2</manvolnum></citerefentry>, and related calls)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>@cpu-emulation</entry>
|
||
<entry>System calls for CPU emulation functionality (<citerefentry project='man-pages'><refentrytitle>vm86</refentrytitle><manvolnum>2</manvolnum></citerefentry> and related calls)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>@debug</entry>
|
||
<entry>Debugging, performance monitoring and tracing functionality (<citerefentry project='man-pages'><refentrytitle>ptrace</refentrytitle><manvolnum>2</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>perf_event_open</refentrytitle><manvolnum>2</manvolnum></citerefentry> and related calls)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>@file-system</entry>
|
||
<entry>File system operations: opening, creating files and directories for read and write, renaming and removing them, reading file properties, or creating hard and symbolic links.</entry>
|
||
</row>
|
||
<row>
|
||
<entry>@io-event</entry>
|
||
<entry>Event loop system calls (<citerefentry project='man-pages'><refentrytitle>poll</refentrytitle><manvolnum>2</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>select</refentrytitle><manvolnum>2</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>eventfd</refentrytitle><manvolnum>2</manvolnum></citerefentry> and related calls)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>@ipc</entry>
|
||
<entry>Pipes, SysV IPC, POSIX Message Queues and other IPC (<citerefentry project='man-pages'><refentrytitle>mq_overview</refentrytitle><manvolnum>7</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>svipc</refentrytitle><manvolnum>7</manvolnum></citerefentry>)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>@keyring</entry>
|
||
<entry>Kernel keyring access (<citerefentry project='man-pages'><refentrytitle>keyctl</refentrytitle><manvolnum>2</manvolnum></citerefentry> and related calls)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>@module</entry>
|
||
<entry>Loading and unloading of kernel modules (<citerefentry project='man-pages'><refentrytitle>init_module</refentrytitle><manvolnum>2</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>delete_module</refentrytitle><manvolnum>2</manvolnum></citerefentry> and related calls)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>@mount</entry>
|
||
<entry>Mounting and unmounting of file systems (<citerefentry project='man-pages'><refentrytitle>mount</refentrytitle><manvolnum>2</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>2</manvolnum></citerefentry>, and related calls)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>@network-io</entry>
|
||
<entry>Socket I/O (including local AF_UNIX): <citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>unix</refentrytitle><manvolnum>7</manvolnum></citerefentry></entry>
|
||
</row>
|
||
<row>
|
||
<entry>@obsolete</entry>
|
||
<entry>Unusual, obsolete or unimplemented (<citerefentry project='man-pages'><refentrytitle>create_module</refentrytitle><manvolnum>2</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>gtty</refentrytitle><manvolnum>2</manvolnum></citerefentry>, …)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>@privileged</entry>
|
||
<entry>All system calls which need super-user capabilities (<citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>@process</entry>
|
||
<entry>Process control, execution, namespaceing operations (<citerefentry project='man-pages'><refentrytitle>clone</refentrytitle><manvolnum>2</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>kill</refentrytitle><manvolnum>2</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>namespaces</refentrytitle><manvolnum>7</manvolnum></citerefentry>, …</entry>
|
||
</row>
|
||
<row>
|
||
<entry>@raw-io</entry>
|
||
<entry>Raw I/O port access (<citerefentry project='man-pages'><refentrytitle>ioperm</refentrytitle><manvolnum>2</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>iopl</refentrytitle><manvolnum>2</manvolnum></citerefentry>, <function>pciconfig_read()</function>, …)</entry>
|
||
</row>
|
||
<row>
|
||
<entry>@resources</entry>
|
||
<entry>System calls for changing resource limits, memory and scheduling parameters (<citerefentry project='man-pages'><refentrytitle>setrlimit</refentrytitle><manvolnum>2</manvolnum></citerefentry>, <citerefentry project='man-pages'><refentrytitle>setpriority</refentrytitle><manvolnum>2</manvolnum></citerefentry>, …)</entry>
|
||
</row>
|
||
</tbody>
|
||
</tgroup>
|
||
</table>
|
||
|
||
Note, that as new system calls are added to the kernel, additional system calls might be
|
||
added to the groups above. Contents of the sets may also change between systemd
|
||
versions. In addition, the list of system calls depends on the kernel version and
|
||
architecture for which systemd was compiled. Use
|
||
<command>systemd-analyze syscall-filter</command> to list the actual list of system calls in
|
||
each filter.
|
||
</para>
|
||
|
||
<para>It is recommended to combine the file system namespacing related options with
|
||
<varname>SystemCallFilter=~@mount</varname>, in order to prohibit the unit's processes to undo the
|
||
mappings. Specifically these are the options <varname>PrivateTmp=</varname>,
|
||
<varname>PrivateDevices=</varname>, <varname>ProtectSystem=</varname>, <varname>ProtectHome=</varname>,
|
||
<varname>ProtectKernelTunables=</varname>, <varname>ProtectControlGroups=</varname>,
|
||
<varname>ReadOnlyPaths=</varname>, <varname>InaccessiblePaths=</varname> and
|
||
<varname>ReadWritePaths=</varname>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>SystemCallErrorNumber=</varname></term>
|
||
|
||
<listitem><para>Takes an <literal>errno</literal> error number
|
||
name to return when the system call filter configured with
|
||
<varname>SystemCallFilter=</varname> is triggered, instead of
|
||
terminating the process immediately. Takes an error name such
|
||
as <constant>EPERM</constant>, <constant>EACCES</constant> or
|
||
<constant>EUCLEAN</constant>. When this setting is not used,
|
||
or when the empty string is assigned, the process will be
|
||
terminated immediately when the filter is
|
||
triggered.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>SystemCallArchitectures=</varname></term>
|
||
|
||
<listitem><para>Takes a space-separated list of architecture identifiers to
|
||
include in the system call filter. The known architecture identifiers are the same
|
||
as for <varname>ConditionArchitecture=</varname> described in
|
||
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
||
as well as <constant>x32</constant>, <constant>mips64-n32</constant>,
|
||
<constant>mips64-le-n32</constant>, and the special identifier
|
||
<constant>native</constant>. Only system calls of the specified architectures will
|
||
be permitted to processes of this unit. This is an effective way to disable
|
||
compatibility with non-native architectures for processes, for example to prohibit
|
||
execution of 32-bit x86 binaries on 64-bit x86-64 systems. The special
|
||
<constant>native</constant> identifier implicitly maps to the native architecture
|
||
of the system (or more strictly: to the architecture the system manager is
|
||
compiled for). If running in user mode, or in system mode, but without the
|
||
<constant>CAP_SYS_ADMIN</constant> capability (e.g. setting
|
||
<varname>User=nobody</varname>), <varname>NoNewPrivileges=yes</varname> is
|
||
implied. Note that setting this option to a non-empty list implies that
|
||
<constant>native</constant> is included too. By default, this option is set to the
|
||
empty list, i.e. no architecture system call filtering is applied.
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>RestrictAddressFamilies=</varname></term>
|
||
|
||
<listitem><para>Restricts the set of socket address families
|
||
accessible to the processes of this unit. Takes a
|
||
space-separated list of address family names to whitelist,
|
||
such as
|
||
<constant>AF_UNIX</constant>,
|
||
<constant>AF_INET</constant> or
|
||
<constant>AF_INET6</constant>. When
|
||
prefixed with <constant>~</constant> the listed address
|
||
families will be applied as blacklist, otherwise as whitelist.
|
||
Note that this restricts access to the
|
||
<citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>2</manvolnum></citerefentry>
|
||
system call only. Sockets passed into the process by other
|
||
means (for example, by using socket activation with socket
|
||
units, see
|
||
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
|
||
are unaffected. Also, sockets created with
|
||
<function>socketpair()</function> (which creates connected
|
||
AF_UNIX sockets only) are unaffected. Note that this option
|
||
has no effect on 32-bit x86 and is ignored (but works
|
||
correctly on x86-64). If running in user mode, or in system
|
||
mode, but without the <constant>CAP_SYS_ADMIN</constant>
|
||
capability (e.g. setting <varname>User=nobody</varname>),
|
||
<varname>NoNewPrivileges=yes</varname> is implied. By
|
||
default, no restriction applies, all address families are
|
||
accessible to processes. If assigned the empty string, any
|
||
previous list changes are undone.</para>
|
||
|
||
<para>Use this option to limit exposure of processes to remote
|
||
systems, in particular via exotic network protocols. Note that
|
||
in most cases, the local <constant>AF_UNIX</constant> address
|
||
family should be included in the configured whitelist as it is
|
||
frequently used for local communication, including for
|
||
<citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>2</manvolnum></citerefentry>
|
||
logging. This does not affect commands prefixed with <literal>+</literal>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>RestrictNamespaces=</varname></term>
|
||
|
||
<listitem><para>Restricts access to Linux namespace functionality for the processes of this unit. For details
|
||
about Linux namespaces, see
|
||
<citerefentry><refentrytitle>namespaces</refentrytitle><manvolnum>7</manvolnum></citerefentry>. Either takes a
|
||
boolean argument, or a space-separated list of namespace type identifiers. If false (the default), no
|
||
restrictions on namespace creation and switching are made. If true, access to any kind of namespacing is
|
||
prohibited. Otherwise, a space-separated list of namespace type identifiers must be specified, consisting of
|
||
any combination of: <constant>cgroup</constant>, <constant>ipc</constant>, <constant>net</constant>,
|
||
<constant>mnt</constant>, <constant>pid</constant>, <constant>user</constant> and <constant>uts</constant>. Any
|
||
namespace type listed is made accessible to the unit's processes, access to namespace types not listed is
|
||
prohibited (whitelisting). By prepending the list with a single tilda character (<literal>~</literal>) the
|
||
effect may be inverted: only the listed namespace types will be made inaccessible, all unlisted ones are
|
||
permitted (blacklisting). If the empty string is assigned, the default namespace restrictions are applied,
|
||
which is equivalent to false. Internally, this setting limits access to the
|
||
<citerefentry><refentrytitle>unshare</refentrytitle><manvolnum>2</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>clone</refentrytitle><manvolnum>2</manvolnum></citerefentry> and
|
||
<citerefentry><refentrytitle>setns</refentrytitle><manvolnum>2</manvolnum></citerefentry> system calls, taking
|
||
the specified flags parameters into account. Note that — if this option is used — in addition to restricting
|
||
creation and switching of the specified types of namespaces (or all of them, if true) access to the
|
||
<function>setns()</function> system call with a zero flags parameter is prohibited.
|
||
If running in user mode, or in system mode, but without the <constant>CAP_SYS_ADMIN</constant>
|
||
capability (e.g. setting <varname>User=</varname>), <varname>NoNewPrivileges=yes</varname>
|
||
is implied.
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>Personality=</varname></term>
|
||
|
||
<listitem><para>Controls which kernel architecture <citerefentry
|
||
project='man-pages'><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry> shall report,
|
||
when invoked by unit processes. Takes one of the architecture identifiers <constant>x86</constant>,
|
||
<constant>x86-64</constant>, <constant>ppc</constant>, <constant>ppc-le</constant>, <constant>ppc64</constant>,
|
||
<constant>ppc64-le</constant>, <constant>s390</constant> or <constant>s390x</constant>. Which personality
|
||
architectures are supported depends on the system architecture. Usually the 64bit versions of the various
|
||
system architectures support their immediate 32bit personality architecture counterpart, but no others. For
|
||
example, <constant>x86-64</constant> systems support the <constant>x86-64</constant> and
|
||
<constant>x86</constant> personalities but no others. The personality feature is useful when running 32-bit
|
||
services on a 64-bit host system. If not specified, the personality is left unmodified and thus reflects the
|
||
personality of the host system's kernel.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>RuntimeDirectory=</varname></term>
|
||
<term><varname>RuntimeDirectoryMode=</varname></term>
|
||
|
||
<listitem><para>Takes a list of directory names. If set, one
|
||
or more directories by the specified names will be created
|
||
below <filename>/run</filename> (for system services) or below
|
||
<varname>$XDG_RUNTIME_DIR</varname> (for user services) when
|
||
the unit is started, and removed when the unit is stopped. The
|
||
directories will have the access mode specified in
|
||
<varname>RuntimeDirectoryMode=</varname>, and will be owned by
|
||
the user and group specified in <varname>User=</varname> and
|
||
<varname>Group=</varname>. Use this to manage one or more
|
||
runtime directories of the unit and bind their lifetime to the
|
||
daemon runtime. The specified directory names must be
|
||
relative, and may not include a <literal>/</literal>, i.e.
|
||
must refer to simple directories to create or remove. This is
|
||
particularly useful for unprivileged daemons that cannot
|
||
create runtime directories in <filename>/run</filename> due to
|
||
lack of privileges, and to make sure the runtime directory is
|
||
cleaned up automatically after use. For runtime directories
|
||
that require more complex or different configuration or
|
||
lifetime guarantees, please consider using
|
||
<citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>MemoryDenyWriteExecute=</varname></term>
|
||
|
||
<listitem><para>Takes a boolean argument. If set, attempts to create memory mappings that are writable and
|
||
executable at the same time, or to change existing memory mappings to become executable, or mapping shared memory
|
||
segments as executable are prohibited.
|
||
Specifically, a system call filter is added that rejects
|
||
<citerefentry><refentrytitle>mmap</refentrytitle><manvolnum>2</manvolnum></citerefentry>
|
||
system calls with both <constant>PROT_EXEC</constant> and <constant>PROT_WRITE</constant> set,
|
||
<citerefentry><refentrytitle>mprotect</refentrytitle><manvolnum>2</manvolnum></citerefentry>
|
||
system calls with <constant>PROT_EXEC</constant> set and
|
||
<citerefentry><refentrytitle>shmat</refentrytitle><manvolnum>2</manvolnum></citerefentry>
|
||
system calls with <constant>SHM_EXEC</constant> set. Note that this option is incompatible with programs
|
||
that generate program code dynamically at runtime, such as JIT execution engines, or programs compiled making
|
||
use of the code "trampoline" feature of various C compilers. This option improves service security, as it makes
|
||
harder for software exploits to change running code dynamically.
|
||
If running in user mode, or in system mode, but without the <constant>CAP_SYS_ADMIN</constant>
|
||
capability (e.g. setting <varname>User=</varname>), <varname>NoNewPrivileges=yes</varname>
|
||
is implied.
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>RestrictRealtime=</varname></term>
|
||
|
||
<listitem><para>Takes a boolean argument. If set, any attempts to enable realtime scheduling in a process of
|
||
the unit are refused. This restricts access to realtime task scheduling policies such as
|
||
<constant>SCHED_FIFO</constant>, <constant>SCHED_RR</constant> or <constant>SCHED_DEADLINE</constant>. See
|
||
<citerefentry project='man-pages'><refentrytitle>sched</refentrytitle><manvolnum>7</manvolnum></citerefentry> for details about
|
||
these scheduling policies. If running in user mode, or in system mode, but
|
||
without the <constant>CAP_SYS_ADMIN</constant> capability
|
||
(e.g. setting <varname>User=</varname>), <varname>NoNewPrivileges=yes</varname>
|
||
is implied. Realtime scheduling policies may be used to monopolize CPU time for longer periods
|
||
of time, and may hence be used to lock up or otherwise trigger Denial-of-Service situations on the system. It
|
||
is hence recommended to restrict access to realtime scheduling to the few programs that actually require
|
||
them. Defaults to off.</para></listitem>
|
||
</varlistentry>
|
||
|
||
</variablelist>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>Environment variables in spawned processes</title>
|
||
|
||
<para>Processes started by the system are executed in a clean
|
||
environment in which select variables listed below are set. System
|
||
processes started by systemd do not inherit variables from PID 1,
|
||
but processes started by user systemd instances inherit all
|
||
environment variables from the user systemd instance.
|
||
</para>
|
||
|
||
<variablelist class='environment-variables'>
|
||
<varlistentry>
|
||
<term><varname>$PATH</varname></term>
|
||
|
||
<listitem><para>Colon-separated list of directories to use
|
||
when launching executables. Systemd uses a fixed value of
|
||
<filename>/usr/local/sbin</filename>:<filename>/usr/local/bin</filename>:<filename>/usr/sbin</filename>:<filename>/usr/bin</filename>:<filename>/sbin</filename>:<filename>/bin</filename>.
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>$LANG</varname></term>
|
||
|
||
<listitem><para>Locale. Can be set in
|
||
<citerefentry project='man-pages'><refentrytitle>locale.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
|
||
or on the kernel command line (see
|
||
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
||
and
|
||
<citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>).
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>$USER</varname></term>
|
||
<term><varname>$LOGNAME</varname></term>
|
||
<term><varname>$HOME</varname></term>
|
||
<term><varname>$SHELL</varname></term>
|
||
|
||
<listitem><para>User name (twice), home directory, and the
|
||
login shell. The variables are set for the units that have
|
||
<varname>User=</varname> set, which includes user
|
||
<command>systemd</command> instances. See
|
||
<citerefentry project='die-net'><refentrytitle>passwd</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>$INVOCATION_ID</varname></term>
|
||
|
||
<listitem><para>Contains a randomized, unique 128bit ID identifying each runtime cycle of the unit, formatted
|
||
as 32 character hexadecimal string. A new ID is assigned each time the unit changes from an inactive state into
|
||
an activating or active state, and may be used to identify this specific runtime cycle, in particular in data
|
||
stored offline, such as the journal. The same ID is passed to all processes run as part of the
|
||
unit.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>$XDG_RUNTIME_DIR</varname></term>
|
||
|
||
<listitem><para>The directory for volatile state. Set for the
|
||
user <command>systemd</command> instance, and also in user
|
||
sessions. See
|
||
<citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>$XDG_SESSION_ID</varname></term>
|
||
<term><varname>$XDG_SEAT</varname></term>
|
||
<term><varname>$XDG_VTNR</varname></term>
|
||
|
||
<listitem><para>The identifier of the session, the seat name,
|
||
and virtual terminal of the session. Set by
|
||
<citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
|
||
for login sessions. <varname>$XDG_SEAT</varname> and
|
||
<varname>$XDG_VTNR</varname> will only be set when attached to
|
||
a seat and a tty.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>$MAINPID</varname></term>
|
||
|
||
<listitem><para>The PID of the unit's main process if it is
|
||
known. This is only set for control processes as invoked by
|
||
<varname>ExecReload=</varname> and similar. </para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>$MANAGERPID</varname></term>
|
||
|
||
<listitem><para>The PID of the user <command>systemd</command>
|
||
instance, set for processes spawned by it. </para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>$LISTEN_FDS</varname></term>
|
||
<term><varname>$LISTEN_PID</varname></term>
|
||
<term><varname>$LISTEN_FDNAMES</varname></term>
|
||
|
||
<listitem><para>Information about file descriptors passed to a
|
||
service for socket activation. See
|
||
<citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>$NOTIFY_SOCKET</varname></term>
|
||
|
||
<listitem><para>The socket
|
||
<function>sd_notify()</function> talks to. See
|
||
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>$WATCHDOG_PID</varname></term>
|
||
<term><varname>$WATCHDOG_USEC</varname></term>
|
||
|
||
<listitem><para>Information about watchdog keep-alive notifications. See
|
||
<citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>$TERM</varname></term>
|
||
|
||
<listitem><para>Terminal type, set only for units connected to
|
||
a terminal (<varname>StandardInput=tty</varname>,
|
||
<varname>StandardOutput=tty</varname>, or
|
||
<varname>StandardError=tty</varname>). See
|
||
<citerefentry project='man-pages'><refentrytitle>termcap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
|
||
</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>$JOURNAL_STREAM</varname></term>
|
||
|
||
<listitem><para>If the standard output or standard error output of the executed processes are connected to the
|
||
journal (for example, by setting <varname>StandardError=journal</varname>) <varname>$JOURNAL_STREAM</varname>
|
||
contains the device and inode numbers of the connection file descriptor, formatted in decimal, separated by a
|
||
colon (<literal>:</literal>). This permits invoked processes to safely detect whether their standard output or
|
||
standard error output are connected to the journal. The device and inode numbers of the file descriptors should
|
||
be compared with the values set in the environment variable to determine whether the process output is still
|
||
connected to the journal. Note that it is generally not sufficient to only check whether
|
||
<varname>$JOURNAL_STREAM</varname> is set at all as services might invoke external processes replacing their
|
||
standard output or standard error output, without unsetting the environment variable.</para>
|
||
|
||
<para>This environment variable is primarily useful to allow services to optionally upgrade their used log
|
||
protocol to the native journal protocol (using
|
||
<citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>3</manvolnum></citerefentry> and other
|
||
functions) if their standard output or standard error output is connected to the journal anyway, thus enabling
|
||
delivery of structured metadata along with logged messages.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>$SERVICE_RESULT</varname></term>
|
||
|
||
<listitem><para>Only defined for the service unit type, this environment variable is passed to all
|
||
<varname>ExecStop=</varname> and <varname>ExecStopPost=</varname> processes, and encodes the service
|
||
"result". Currently, the following values are defined: <literal>protocol</literal> (in case of a protocol
|
||
violation; if a service did not take the steps required by its unit configuration), <literal>timeout</literal>
|
||
(in case of an operation timeout), <literal>exit-code</literal> (if a service process exited with a non-zero
|
||
exit code; see <varname>$EXIT_CODE</varname> below for the actual exit code returned), <literal>signal</literal>
|
||
(if a service process was terminated abnormally by a signal; see <varname>$EXIT_CODE</varname> below for the
|
||
actual signal used for the termination), <literal>core-dump</literal> (if a service process terminated
|
||
abnormally and dumped core), <literal>watchdog</literal> (if the watchdog keep-alive ping was enabled for the
|
||
service but it missed the deadline), or <literal>resources</literal> (a catch-all condition in case a system
|
||
operation failed).</para>
|
||
|
||
<para>This environment variable is useful to monitor failure or successful termination of a service. Even
|
||
though this variable is available in both <varname>ExecStop=</varname> and <varname>ExecStopPost=</varname>, it
|
||
is usually a better choice to place monitoring tools in the latter, as the former is only invoked for services
|
||
that managed to start up correctly, and the latter covers both services that failed during their start-up and
|
||
those which failed during their runtime.</para></listitem>
|
||
</varlistentry>
|
||
|
||
<varlistentry>
|
||
<term><varname>$EXIT_CODE</varname></term>
|
||
<term><varname>$EXIT_STATUS</varname></term>
|
||
|
||
<listitem><para>Only defined for the service unit type, these environment variables are passed to all
|
||
<varname>ExecStop=</varname>, <varname>ExecStopPost=</varname> processes and contain exit status/code
|
||
information of the main process of the service. For the precise definition of the exit code and status, see
|
||
<citerefentry><refentrytitle>wait</refentrytitle><manvolnum>2</manvolnum></citerefentry>. <varname>$EXIT_CODE</varname>
|
||
is one of <literal>exited</literal>, <literal>killed</literal>,
|
||
<literal>dumped</literal>. <varname>$EXIT_STATUS</varname> contains the numeric exit code formatted as string
|
||
if <varname>$EXIT_CODE</varname> is <literal>exited</literal>, and the signal name in all other cases. Note
|
||
that these environment variables are only set if the service manager succeeded to start and identify the main
|
||
process of the service.</para>
|
||
|
||
<table>
|
||
<title>Summary of possible service result variable values</title>
|
||
<tgroup cols='3'>
|
||
<colspec colname='result' />
|
||
<colspec colname='code' />
|
||
<colspec colname='status' />
|
||
<thead>
|
||
<row>
|
||
<entry><varname>$SERVICE_RESULT</varname></entry>
|
||
<entry><varname>$EXIT_CODE</varname></entry>
|
||
<entry><varname>$EXIT_STATUS</varname></entry>
|
||
</row>
|
||
</thead>
|
||
|
||
<tbody>
|
||
<row>
|
||
<entry morerows="1" valign="top"><literal>protocol</literal></entry>
|
||
<entry valign="top">not set</entry>
|
||
<entry>not set</entry>
|
||
</row>
|
||
<row>
|
||
<entry><literal>exited</literal></entry>
|
||
<entry><literal>0</literal></entry>
|
||
</row>
|
||
|
||
<row>
|
||
<entry morerows="1" valign="top"><literal>timeout</literal></entry>
|
||
<entry valign="top"><literal>killed</literal></entry>
|
||
<entry><literal>TERM</literal>, <literal>KILL</literal></entry>
|
||
</row>
|
||
<row>
|
||
<entry valign="top"><literal>exited</literal></entry>
|
||
<entry><literal>0</literal>, <literal>1</literal>, <literal>2</literal>, <literal
|
||
>3</literal>, …, <literal>255</literal></entry>
|
||
</row>
|
||
|
||
<row>
|
||
<entry valign="top"><literal>exit-code</literal></entry>
|
||
<entry valign="top"><literal>exited</literal></entry>
|
||
<entry><literal>0</literal>, <literal>1</literal>, <literal>2</literal>, <literal
|
||
>3</literal>, …, <literal>255</literal></entry>
|
||
</row>
|
||
|
||
<row>
|
||
<entry valign="top"><literal>signal</literal></entry>
|
||
<entry valign="top"><literal>killed</literal></entry>
|
||
<entry><literal>HUP</literal>, <literal>INT</literal>, <literal>KILL</literal>, …</entry>
|
||
</row>
|
||
|
||
<row>
|
||
<entry valign="top"><literal>core-dump</literal></entry>
|
||
<entry valign="top"><literal>dumped</literal></entry>
|
||
<entry><literal>ABRT</literal>, <literal>SEGV</literal>, <literal>QUIT</literal>, …</entry>
|
||
</row>
|
||
|
||
<row>
|
||
<entry morerows="2" valign="top"><literal>watchdog</literal></entry>
|
||
<entry><literal>dumped</literal></entry>
|
||
<entry><literal>ABRT</literal></entry>
|
||
</row>
|
||
<row>
|
||
<entry><literal>killed</literal></entry>
|
||
<entry><literal>TERM</literal>, <literal>KILL</literal></entry>
|
||
</row>
|
||
<row>
|
||
<entry><literal>exited</literal></entry>
|
||
<entry><literal>0</literal>, <literal>1</literal>, <literal>2</literal>, <literal
|
||
>3</literal>, …, <literal>255</literal></entry>
|
||
</row>
|
||
|
||
<row>
|
||
<entry><literal>resources</literal></entry>
|
||
<entry>any of the above</entry>
|
||
<entry>any of the above</entry>
|
||
</row>
|
||
|
||
<row>
|
||
<entry namest="results" nameend="code">Note: the process may be also terminated by a signal not sent by systemd. In particular the process may send an arbitrary signal to itself in a handler for any of the non-maskable signals. Nevertheless, in the <literal>timeout</literal> and <literal>watchdog</literal> rows above only the signals that systemd sends have been included.</entry>
|
||
</row>
|
||
</tbody>
|
||
</tgroup>
|
||
</table>
|
||
|
||
</listitem>
|
||
</varlistentry>
|
||
</variablelist>
|
||
|
||
<para>Additional variables may be configured by the following
|
||
means: for processes spawned in specific units, use the
|
||
<varname>Environment=</varname>, <varname>EnvironmentFile=</varname>
|
||
and <varname>PassEnvironment=</varname> options above; to specify
|
||
variables globally, use <varname>DefaultEnvironment=</varname>
|
||
(see
|
||
<citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
|
||
or the kernel option <varname>systemd.setenv=</varname> (see
|
||
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>).
|
||
Additional variables may also be set through PAM,
|
||
cf. <citerefentry project='man-pages'><refentrytitle>pam_env</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
|
||
</refsect1>
|
||
|
||
<refsect1>
|
||
<title>See Also</title>
|
||
<para>
|
||
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
|
||
<citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
||
<citerefentry project='man-pages'><refentrytitle>exec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
||
</para>
|
||
</refsect1>
|
||
|
||
|
||
</refentry>
|