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11a1589223
Files which are installed as-is (any .service and other unit files, .conf files, .policy files, etc), are left as is. My assumption is that SPDX identifiers are not yet that well known, so it's better to retain the extended header to avoid any doubt. I also kept any copyright lines. We can probably remove them, but it'd nice to obtain explicit acks from all involved authors before doing that.
156 lines
8.2 KiB
XML
156 lines
8.2 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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SPDX-License-Identifier: LGPL-2.1+
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This file is part of systemd.
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Copyright 2014 Zbigniew Jędrzejewski-Szmek
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-->
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<refentry id="systemd-coredump" conditional='ENABLE_COREDUMP'
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>systemd-coredump</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-coredump</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-coredump</refname>
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<refname>systemd-coredump.socket</refname>
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<refname>systemd-coredump@.service</refname>
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<refpurpose>Acquire, save and process core dumps</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>/usr/lib/systemd/systemd-coredump</filename></para>
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<para><filename>/usr/lib/systemd/systemd-coredump</filename> <option>--backtrace</option></para>
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<para><filename>systemd-coredump@.service</filename></para>
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<para><filename>systemd-coredump.socket</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-coredump@.service</filename> is a system service that can acquire core
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dumps from the kernel and handle them in various ways. The <command>systemd-coredump</command>
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executable does the actual work. It is invoked twice: once as the handler by the kernel, and the
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second time in the <filename>systemd-coredump@.service</filename> to actually write the data to
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the journal.</para>
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<para>When the kernel invokes <command>systemd-coredump</command> to handle a core dump, it runs
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in privileged mode, and will connect to the socket created by the
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<filename>systemd-coredump.socket</filename> unit, which in turn will spawn an unprivileged
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<filename>systemd-coredump@.service</filename> instance to process the core dump. Hence
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<filename>systemd-coredump.socket</filename> and <filename>systemd-coredump@.service</filename>
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are helper units which do the actual processing of core dumps and are subject to normal service
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management.</para>
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<para>Core dumps can be written to the journal or saved as a file. Once saved they can be retrieved
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for further processing, for example in
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<citerefentry project='man-pages'><refentrytitle>gdb</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
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</para>
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<para>By default, <command>systemd-coredump</command> will log the core dump including a backtrace
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if possible to the journal and store the core dump itself in an external file in
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<filename>/var/lib/systemd/coredump</filename>.</para>
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<para>The behavior of a specific program upon reception of a signal is governed by a few
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factors which are described in detail in
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<citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
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In particular, the core dump will only be processed when the related resource limits are sufficient.
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</para>
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<para>It is also possible to invoke <command>systemd-coredump</command> with
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<option>--backtrace</option> option. In this case, <command>systemd-coredump</command> expects
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a journal entry in the journal
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<ulink url="https://www.freedesktop.org/wiki/Software/systemd/export">Journal Export Format</ulink>
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on standard input. The entry should contain a <varname>MESSAGE=</varname> field and any additional
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metadata fields the caller deems reasonable. <command>systemd-coredump</command> will append
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additional metadata fields in the same way it does for core dumps received from the kernel. In
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this mode, no core dump is stored in the journal.</para>
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</refsect1>
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<refsect1>
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<title>Configuration</title>
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<para>For programs started by <command>systemd</command> process resource limits can be set by directive
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<varname>LimitCore=</varname>, see
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<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
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</para>
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<para>In order to be used by the kernel to handle core dumps,
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<command>systemd-coredump</command> must be configured in
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<citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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parameter <varname>kernel.core_pattern</varname>. The syntax of this parameter is explained in
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<citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
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systemd installs the file <filename>/usr/lib/sysctl.d/50-coredump.conf</filename> which configures
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<varname>kernel.core_pattern</varname> accordingly. This file may be masked or overridden to use a different
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setting following normal
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<citerefentry><refentrytitle>sysctl.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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rules. If the sysctl configuration is modified, it must be updated in the kernel before it
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takes effect, see
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<citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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and
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<citerefentry><refentrytitle>systemd-sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
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</para>
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<para>In order to by used in the <option>--backtrace</option> mode, an appropriate backtrace
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handler must be installed on the sender side. For example, in case of
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<citerefentry project='die-net'><refentrytitle>python</refentrytitle><manvolnum>1</manvolnum></citerefentry>, this
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means a <varname>sys.excepthook</varname> must installed, see
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<ulink url="https://github.com/keszybz/systemd-coredump-python">systemd-coredump-python</ulink>.
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</para>
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<para>The behavior of <command>systemd-coredump</command> itself is configured through the configuration file
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<filename>/etc/systemd/coredump.conf</filename> and corresponding snippets
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<filename>/etc/systemd/coredump.conf.d/*.conf</filename>, see
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<citerefentry><refentrytitle>coredump.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>. A new
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instance of <command>systemd-coredump</command> is invoked upon receiving every core dump. Therefore, changes
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in these files will take effect the next time a core dump is received.</para>
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<para>Resources used by core dump files are restricted in two ways. Parameters like maximum size of acquired
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core dumps and files can be set in files <filename>/etc/systemd/coredump.conf</filename> and snippets mentioned
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above. In addition the storage time of core dump files is restricted by <command>systemd-tmpfiles</command>,
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corresponding settings are by default in <filename>/usr/lib/tmpfiles.d/systemd.conf</filename>.</para>
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</refsect1>
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<refsect1>
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<title>Usage</title>
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<para>Data stored in the journal can be viewed with
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<citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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as usual.
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<citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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can be used to retrieve saved core dumps independent of their location, to display information and to process
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them e.g. by passing to the GNU debugger (gdb).</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>coredump.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-tmpfiles</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sysctl.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
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</para>
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</refsect1>
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</refentry>
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