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a24c64f03f
Previously all journal files were owned by "adm". In order to allow specific users to read the journal files without granting it access to the full "adm" powers, introduce a new specific group for this. "systemd-journal" has to be created by the packaging scripts manually at installation time. It's a good idea to assign a static UID/GID to this group, since /var/log/journal might be shared across machines via NFS. This commit also grants read access to the journal files by default to members of the "wheel" and "adm" groups via file system ACLs, since these "almost-root" groups should be able to see what's going on on the system. These ACLs are created by "make install". Packagers probably need to duplicate this logic in their postinst scripts. This also adds documentation how to grant access to the journal to additional users or groups via fs ACLs.
207 lines
9.4 KiB
XML
207 lines
9.4 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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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-journald.service">
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<refentryinfo>
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<title>systemd-journald.service</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-journald.service</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-journald.service</refname>
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<refname>systemd-journald.socket</refname>
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<refname>systemd-journald</refname>
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<refpurpose>Journal service</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>systemd-journald.service</filename></para>
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<para><filename>systemd-journald.socket</filename></para>
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<para><filename>/usr/lib/systemd/systemd-journald</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><filename>systemd-journald</filename> is a
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system service that collects and stores logging
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data. It creates and maintains structured, indexed
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journals based on logging information that is received
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from the kernel, from user processes via the libc
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<citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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call, from STDOUT/STDERR of system services or via its
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native API. It will implicitly collect numerous meta
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data fields for each log messages in a secure and
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unfakeable way. See
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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for more information about the collected meta data.
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</para>
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<para>Log data collected by the journal is primarily
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text based but can also include binary data where
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necessary. All objects stored in the journal can be up
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to 2^64-1 bytes in size.</para>
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<para>By default the journal stores log data in
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<filename>/run/log/journal/</filename>. Since
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<filename>/run/</filename> is volatile log data is
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lost at reboot. To make the data persistent it
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is sufficient to create
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<filename>/var/log/journal/</filename> where
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<filename>systemd-journald</filename> will then store
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the data.</para>
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<para><filename>systemd-journald</filename> will
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forward all received log messages to the AF_UNIX
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SOCK_DGRAM socket
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<filename>/run/systemd/journal/syslog</filename> (if it exists) which
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may be used by UNIX syslog daemons to process the data
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further.</para>
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<para>See
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<citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for information about the configuration of this
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service.</para>
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</refsect1>
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<refsect1>
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<title>Signals</title>
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<variablelist>
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<varlistentry>
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<term>SIGUSR1</term>
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<listitem><para>Request that journal
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data from <filename>/run/</filename>
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is flushed to
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<filename>/var/</filename> in order to
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make it persistent (if this is
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enabled). This may be used after
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<filename>/var/</filename> is mounted,
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but is generally not required since
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the first journal write when
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<filename>/var/</filename> becomes
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writable triggers the flushing
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anyway.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>SIGUSR2</term>
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<listitem><para>Request immediate
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rotation of the journal
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files.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Kernel Command Line</title>
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<para>A few configuration parameters from
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<filename>journald.conf</filename> may be overridden on
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the kernel command line:</para>
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<variablelist class='kernel-commandline-options'>
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<varlistentry>
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<term><varname>systemd.journald.forward_to_syslog=</varname></term>
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<term><varname>systemd.journald.forward_to_kmsg=</varname></term>
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<term><varname>systemd.journald.forward_to_console=</varname></term>
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<listitem><para>Enables/disables
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forwarding of collected log messages
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to syslog, the kernel log buffer or
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the system console.
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</para>
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<para>See
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<citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for information about these settings.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Access Control</title>
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<para>Journal files are by default owned and readable
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by the <literal>systemd-journal</literal> system group
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(but not writable). Adding a user to this group thus
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enables her/him to read the journal files.</para>
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<para>By default, each logged in user will get her/his
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own set of journal files in
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<filename>/var/log/journal/</filename>. These files
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will not be owned by the user however, in order to
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avoid that the user can write to them
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directly. Instead, file system ACLs are used to ensure
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the user gets read access only.</para>
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<para>Additional users and groups may be granted
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access to journal files via file system access control
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lists (ACL). Distributions and administrators may
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choose to grant read access to all members of the
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<literal>wheel</literal> and <literal>adm</literal>
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system groups with a command such as the
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following:</para>
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<programlisting># setfacl -Rnm g:wheel:rx,d:g:wheel:rx,g:adm:rx,d:g:adm:rx /var/log/journal/</programlisting>
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<para>Note that this command will update the ACLs both
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for existing journal files and for future journal
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files created in the
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<filename>/var/log/journal/</filename>
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directory.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>setfacl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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