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diff --git a/man/systemd-coredump.xml b/man/systemd-coredump.xml new file mode 100644 index 0000000..b25f0c4 --- /dev/null +++ b/man/systemd-coredump.xml @@ -0,0 +1,152 @@ +<?xml version='1.0'?> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> + +<!-- + SPDX-License-Identifier: LGPL-2.1+ +--> + +<refentry id="systemd-coredump" conditional='ENABLE_COREDUMP' + xmlns:xi="http://www.w3.org/2001/XInclude"> + + <refentryinfo> + <title>systemd-coredump</title> + <productname>systemd</productname> + </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>/usr/lib/systemd/systemd-coredump</filename> <option>--backtrace</option></para> + <para><filename>systemd-coredump@.service</filename></para> + <para><filename>systemd-coredump.socket</filename></para> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + <para><filename>systemd-coredump@.service</filename> is a system service that can acquire core + dumps from the kernel and handle them in various ways. The <command>systemd-coredump</command> + executable does the actual work. It is invoked twice: once as the handler by the kernel, and the + second time in the <filename>systemd-coredump@.service</filename> to actually write the data to + the journal.</para> + + <para>When the kernel invokes <command>systemd-coredump</command> to handle a core dump, it runs + in privileged mode, and will connect to the socket created by the + <filename>systemd-coredump.socket</filename> unit, which in turn will spawn an unprivileged + <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>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>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> + + <para>It is also possible to invoke <command>systemd-coredump</command> with + <option>--backtrace</option> option. In this case, <command>systemd-coredump</command> expects + a journal entry in the journal + <ulink url="https://www.freedesktop.org/wiki/Software/systemd/export">Journal Export Format</ulink> + on standard input. The entry should contain a <varname>MESSAGE=</varname> field and any additional + metadata fields the caller deems reasonable. <command>systemd-coredump</command> will append + additional metadata fields in the same way it does for core dumps received from the kernel. In + this mode, no core dump is stored in the journal.</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 by the kernel to handle core dumps, + <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>In order to by used in the <option>--backtrace</option> mode, an appropriate backtrace + handler must be installed on the sender side. For example, in case of + <citerefentry project='die-net'><refentrytitle>python</refentrytitle><manvolnum>1</manvolnum></citerefentry>, this + means a <varname>sys.excepthook</varname> must installed, see + <ulink url="https://github.com/keszybz/systemd-coredump-python">systemd-coredump-python</ulink>. + </para> + + <para>The behavior 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> + + <refsect2> + <title>Disabling coredump processing</title> + + <para>To disable potentially resource-intensive processing by <command>systemd-coredump</command>, + set <programlisting>Storage=none +ProcessSizeMax=0</programlisting> in + <citerefentry><refentrytitle>coredump.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>. + </para> + </refsect2> + </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> |