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diff --git a/man/systemd-coredump.xml b/man/systemd-coredump.xml new file mode 100644 index 0000000..0f41c69 --- /dev/null +++ b/man/systemd-coredump.xml @@ -0,0 +1,457 @@ +<?xml version='1.0'?> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> +<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> + +<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 to process core dumps. It will + log a summary of the event to + <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + including information about the process identifier, owner, the signal that killed the process, and the + stack trace if possible. It may also save the core dump for later processing. See the "Information about + the crashed process" section below.</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>Core dumps can be written to the journal or saved as a file. In both cases, they can be retrieved + for further processing, for example in + <citerefentry project='man-pages'><refentrytitle>gdb</refentrytitle><manvolnum>1</manvolnum></citerefentry>. + See <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + in particular the <command>list</command> and <command>debug</command> verbs.</para> + + <para>By default, <command>systemd-coredump</command> will log the core dump to the journal, including a + backtrace if possible, and store the core dump (an image of the memory contents of the process) itself in + an external file in <filename>/var/lib/systemd/coredump</filename>. These core dumps are deleted after a + few days by default; see <filename>/usr/lib/tmpfiles.d/systemd.conf</filename> for details. Note that the + removal of core files from the file system and the purging of journal entries are independent, and the + core file may be present without the journal entry, and journal entries may point to since-removed core + files. Some metadata is attached to core files in the form of extended attributes, so the core files are + useful for some purposes even without the full metadata available in the journal entry.</para> + + <para>For further details see <ulink url="https://systemd.io/COREDUMP">systemd Coredump + Handling</ulink>.</para> + + <refsect2> + <title>Invocation of <command>systemd-coredump</command></title> + + <para>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 and process + and save the core file.</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>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://systemd.io/JOURNAL_EXPORT_FORMATS#journal-export-format">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> + </refsect2> + </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 be 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 be installed, see + <ulink url="https://github.com/systemd/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>. The default is + to delete core dumps after a few days; see the above file for details.</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>Information about the crashed process</title> + + <para><citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> can + be used to retrieve saved core dumps independently of their location, to display information, and to + process them e.g. by passing to the GNU debugger (gdb).</para> + + <para>Data stored in the journal can be also viewed with + <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> as usual + (or from any other process, using the + <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry> API). + The relevant messages have <constant>MESSAGE_ID=fc2e22bc6ee647b6b90729ab34a250b1</constant>:</para> + <programlisting>$ journalctl MESSAGE_ID=fc2e22bc6ee647b6b90729ab34a250b1 -o verbose +… +MESSAGE_ID=fc2e22bc6ee647b6b90729ab34a250b1 +COREDUMP_PID=552351 +COREDUMP_UID=1000 +COREDUMP_GID=1000 +COREDUMP_SIGNAL_NAME=SIGSEGV +COREDUMP_SIGNAL=11 +COREDUMP_TIMESTAMP=1614342930000000 +COREDUMP_COMM=Web Content +COREDUMP_EXE=/usr/lib64/firefox/firefox +COREDUMP_USER_UNIT=app-gnome-firefox-552136.scope +COREDUMP_CMDLINE=/usr/lib64/firefox/firefox -contentproc -childID 5 -isForBrowser … +COREDUMP_CGROUP=/user.slice/user-1000.slice/user@1000.service/app.slice/app-….scope +COREDUMP_FILENAME=/var/lib/systemd/coredump/core.Web….552351.….zst +… + </programlisting> + + <para>The following fields are saved (if known) with the journal entry</para> + + <variablelist class='journal-directives'> + <varlistentry> + <term><varname>COREDUMP_UID=</varname></term> + <term><varname>COREDUMP_PID=</varname></term> + <term><varname>COREDUMP_GID=</varname></term> + <listitem><para>The process number (PID), owner user number (UID), and group number (GID) of the + crashed process.</para> + + <para>When the crashed process was part of a container (or in a process or user namespace in + general), those are the values as seen <emphasis>outside</emphasis>, in the namespace where + <filename>systemd-coredump</filename> is running.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_TIMESTAMP=</varname></term> + <listitem><para>The time of the crash as reported by the kernel (in µs since the epoch).</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_RLIMIT=</varname></term> + <listitem><para>The core file size soft resource limit, see + <citerefentry project='man-pages'><refentrytitle>getrlimit</refentrytitle><manvolnum>2</manvolnum></citerefentry>. + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_UNIT=</varname></term> + <term><varname>COREDUMP_SLICE=</varname></term> + <listitem><para>The system unit and slice names.</para> + + <para>When the crashed process was in container, those are the units names + <emphasis>outside</emphasis>, in the main system manager.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_CGROUP=</varname></term> + + <listitem><para>The primary cgroup of the unit of the crashed process.</para> + + <para>When the crashed process was in a container, this is the full path, as seen outside of the + container.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_PROC_CGROUP=</varname></term> + <listitem><para>Control group information in the format used in + <filename>/proc/self/cgroup</filename>. On systems with the unified cgroup hierarchy, this is a + single path prefixed with <literal>0::</literal>, and multiple paths prefixed with controller numbers + on legacy systems.</para> + + <para>When the crashed process was in a container, this is the full path, as seen outside of the + container.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_OWNER_UID=</varname></term> + <term><varname>COREDUMP_USER_UNIT=</varname></term> + <term><varname>COREDUMP_SESSION=</varname></term> + <listitem><para>The numerical UID of the user owning the login session or systemd user unit of the + crashed process, the user manager unit, and the sesion identifier. All three fields are only present + for user processes.</para> + + <para>When the crashed process was in container, those are the values <emphasis>outside</emphasis>, + in the main system.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_SIGNAL_NAME=</varname></term> + <term><varname>COREDUMP_SIGNAL=</varname></term> + + <listitem><para>The terminating signal name (with the <literal>SIG</literal> prefix + <footnote><para><citerefentry + project='man-pages'><refentrytitle>kill</refentrytitle><manvolnum>1</manvolnum></citerefentry> + expects signal names <emphasis>without</emphasis> the prefix; <citerefentry + project='man-pages'><refentrytitle>kill</refentrytitle><manvolnum>2</manvolnum></citerefentry> uses + the prefix; all systemd tools accept signal names both with and without the prefix. + </para></footnote>) and numerical value. (Both are included because signal numbers vary by + architecture.)</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_CWD=</varname></term> + <term><varname>COREDUMP_ROOT=</varname></term> + + <listitem><para>The current working directory and root directory of the crashed process.</para> + + <para>When the crashed process is in a container, those paths are relative to the root of the + container's mount namespace.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_OPEN_FDS=</varname></term> + + <listitem><para>Information about open file descriptors, in the following format:</para> + <programlisting><replaceable>fd</replaceable>:<replaceable>/path/to/file</replaceable> +pos: ... +flags: ... +... + +<replaceable>fd</replaceable>:<replaceable>/path/to/file</replaceable> +pos: ... +flags: ... +... + </programlisting> + + <para>The first line contains the file descriptor number <replaceable>fd</replaceable> and the path, + while subsequent lines show the contents of + <filename>/proc/<replaceable>pid</replaceable>/fdinfo/<replaceable>fd</replaceable></filename>. + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_EXE=</varname></term> + + <listitem><para>The destination of the <filename>/proc/<replaceable>pid</replaceable>/exe</filename> + symlink.</para> + + <para>When the crashed process is in a container, that path is relative to the root of the + container's mount namespace.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_CMDLINE=</varname></term> + <term><varname>COREDUMP_COMM=</varname></term> + <term><varname>COREDUMP_ENVIRON=</varname></term> + <term><varname>COREDUMP_PROC_AUXV=</varname></term> + <term><varname>COREDUMP_PROC_LIMITS=</varname></term> + <term><varname>COREDUMP_PROC_MAPS=</varname></term> + <term><varname>COREDUMP_PROC_MOUNTINFO=</varname></term> + <term><varname>COREDUMP_PROC_STATUS=</varname></term> + + <listitem><para>Fields that map the per-process entries in the <filename>/proc/</filename> + filesystem: <filename>/proc/<replaceable>pid</replaceable>/cmdline</filename> (the command line of + the crashed process), <filename>/proc/<replaceable>pid</replaceable>/comm</filename> (the command + name associated with the process), <filename>/proc/<replaceable>pid</replaceable>/environ</filename> + (the environment block of the crashed process), + <filename>/proc/<replaceable>pid</replaceable>/auxv</filename> (the auxiliary vector of the crashed + process, see <citerefentry + project='man-pages'><refentrytitle>getauxval</refentrytitle><manvolnum>3</manvolnum></citerefentry>), + <filename>/proc/<replaceable>pid</replaceable>/limits</filename> (the soft and hard resource limits), + <filename>/proc/<replaceable>pid</replaceable>/maps</filename> (memory regions visible to the process + and their access permissions), <filename>/proc/<replaceable>pid</replaceable>/mountinfo</filename> + (mount points in the process's mount namespace), + <filename>/proc/<replaceable>pid</replaceable>/status</filename> (various metadata about the + process).</para> + + <para>See + <citerefentry project='man-pages'><refentrytitle>proc</refentrytitle><manvolnum>5</manvolnum></citerefentry> + for more information.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_HOSTNAME=</varname></term> + + <listitem><para>The system hostname.</para> + + <para>When the crashed process was in container, this is the container hostname.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_CONTAINER_CMDLINE=</varname></term> + + <listitem><para>For processes running in a container, the commandline of the process spawning the + container (the first parent process with a different mount namespace).</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP=</varname></term> + + <listitem><para>When the core is stored in the journal, the core image itself.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_FILENAME=</varname></term> + + <listitem><para>When the core is stored externally, the path to the core file.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_TRUNCATED=</varname></term> + + <listitem><para>Set to <literal>1</literal> when the saved coredump was truncated. (A partial core + image may still be processed by some tools, though obviously not all information is available.) + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>COREDUMP_PACKAGE_NAME=</varname></term> + <term><varname>COREDUMP_PACKAGE_VERSION=</varname></term> + <term><varname>COREDUMP_PACKAGE_JSON=</varname></term> + + <listitem><para>If the executable contained .package metadata ELF notes, they will be + parsed and attached. The <varname>package</varname> and <varname>packageVersion</varname> + of the 'main' ELF module (ie: the executable) will be appended individually. The + JSON-formatted content of all modules will be appended as a single JSON object, each with + the module name as the key. For more information about this metadata format and content, see + <ulink url="https://systemd.io/COREDUMP_PACKAGE_METADATA/">the coredump metadata spec</ulink>.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><varname>MESSAGE=</varname></term> + + <listitem><para>The message generated by <command>systemd-coredump</command> that includes the + backtrace if it was successfully generated. When <command>systemd-coredump</command> is invoked with + <option>--backtrace</option>, this field is provided by the caller.</para></listitem> + </varlistentry> + </variablelist> + + <para>Various other fields exist in the journal entry, but pertain to the logging process, + i.e. <command>systemd-coredump</command>, not the crashed process. See + <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>. + </para> + + <para>The following fields are saved (if known) with the external file listed in + <varname>COREDUMP_FILENAME=</varname> as extended attributes:</para> + + <variablelist> + <varlistentry> + <term><varname>user.coredump.pid</varname></term> + <term><varname>user.coredump.uid</varname></term> + <term><varname>user.coredump.gid</varname></term> + <term><varname>user.coredump.signal</varname></term> + <term><varname>user.coredump.timestamp</varname></term> + <term><varname>user.coredump.rlimit</varname></term> + <term><varname>user.coredump.hostname</varname></term> + <term><varname>user.coredump.comm</varname></term> + <term><varname>user.coredump.exe</varname></term> + + <listitem><para>Those are the same as <varname>COREDUMP_PID=</varname>, + <varname>COREDUMP_UID=</varname>, <varname>COREDUMP_GID=</varname>, + <varname>COREDUMP_SIGNAL=</varname>, <varname>COREDUMP_TIMESTAMP=</varname>, + <varname>COREDUMP_RLIMIT=</varname>, <varname>COREDUMP_HOSTNAME=</varname>, + <varname>COREDUMP_COMM=</varname>, and <varname>COREDUMP_EXE=</varname>, described above. + </para></listitem> + </varlistentry> + </variablelist> + + <para>Those can be viewed using + <citerefentry project='man-pages'><refentrytitle>getfattr</refentrytitle><manvolnum>1</manvolnum></citerefentry>. + For the core file described in the journal entry shown above: + <programlisting>$ getfattr --absolute-names -d /var/lib/systemd/coredump/core.Web….552351.….zst +# file: /var/lib/systemd/coredump/core.Web….552351.….zst +user.coredump.pid="552351" +user.coredump.uid="1000" +user.coredump.gid="1000" +user.coredump.signal="11" +user.coredump.timestamp="1614342930000000" +user.coredump.comm="Web Content" +user.coredump.exe="/usr/lib64/firefox/firefox" +… +</programlisting> + </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>, + <ulink url="https://systemd.io/COREDUMP">systemd Coredump Handling</ulink> + </para> + </refsect1> +</refentry> |