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<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
Copyright 2014 Zbigniew Jędrzejewski-Szmek
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="systemd-coredump" conditional='ENABLE_COREDUMP'
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>systemd-coredump</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>systemd-coredump</refentrytitle>
<manvolnum>8</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd-coredump</refname>
<refname>systemd-coredump.socket</refname>
<refname>systemd-coredump@.service</refname>
<refpurpose>Acquire, save and process core dumps</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>/usr/lib/systemd/systemd-coredump</filename></para>
<para><filename>systemd-coredump@.service</filename></para>
<para><filename>systemd-coredump.socket</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><command>systemd-coredump</command> is a system service that can acquire core dumps
from the kernel and handle them in various ways.</para>
<para>Core dumps can be written to the journal or saved as a file. Once saved they can be retrieved
for further processing, for example in
<citerefentry project='man-pages'><refentrytitle>gdb</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
</para>
<para>By default, <command>systemd-coredump</command> will log the core dump including a backtrace
if possible to the journal and store the core dump itself in an external file in
<filename>/var/lib/systemd/coredump</filename>.</para>
<para>When the kernel invokes <command>systemd-coredump</command> to handle a core dump,
it will connect to the socket created by the <filename>systemd-coredump.socket</filename>
unit, which in turn will spawn a <filename>systemd-coredump@.service</filename> instance
to process the core dump. Hence <filename>systemd-coredump.socket</filename>
and <filename>systemd-coredump@.service</filename> are helper units which do the actual
processing of core dumps and are subject to normal service management.</para>
<para>The behavior of a specific program upon reception of a signal is governed by a few
factors which are described in detail in
<citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
In particular, the core dump will only be processed when the related resource limits are sufficient.
</para>
</refsect1>
<refsect1>
<title>Configuration</title>
<para>For programs started by <command>systemd</command> process resource limits can be set by directive
<varname>LimitCore=</varname>, see
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
<para>In order to be used <command>systemd-coredump</command> must be configured in
<citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>
parameter <varname>kernel.core_pattern</varname>. The syntax of this parameter is explained in
<citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
Systemd installs the file <filename>/usr/lib/sysctl.d/50-coredump.conf</filename> which configures
<varname>kernel.core_pattern</varname> accordingly. This file may be masked or overridden to use a different
setting following normal
<citerefentry><refentrytitle>sysctl.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
rules.
If the sysctl configuration is modified, it must be updated in the kernel before
it takes effect, see
<citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>
and
<citerefentry><refentrytitle>systemd-sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
</para>
<para>The behaviour of <command>systemd-coredump</command> itself is configured through the configuration file
<filename>/etc/systemd/coredump.conf</filename> and corresponding snippets
<filename>/etc/systemd/coredump.conf.d/*.conf</filename>, see
<citerefentry><refentrytitle>coredump.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>. A new
instance of <command>systemd-coredump</command> is invoked upon receiving every core dump. Therefore, changes
in these files will take effect the next time a core dump is received.</para>
<para>Resources used by core dump files are restricted in two ways. Parameters like maximum size of acquired
core dumps and files can be set in files <filename>/etc/systemd/coredump.conf</filename> and snippets mentioned
above. In addition the storage time of core dump files is restricted by <command>systemd-tmpfiles</command>,
corresponding settings are by default in <filename>/usr/lib/tmpfiles.d/systemd.conf</filename>.</para>
</refsect1>
<refsect1>
<title>Usage</title>
<para>Data stored in the journal can be viewed with
<citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
as usual.
<citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
can be used to retrieve saved core dumps independent of their location, to display information and to process
them e.g. by passing to the GNU debugger (gdb).</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>coredump.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-tmpfiles</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sysctl.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
</para>
</refsect1>
</refentry>
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