man/systemd-pstore.service.xml

   1 <?xml version='1.0'?>
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="systemd-pstore" conditional='ENABLE_PSTORE'
   7           xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>systemd-pstore.service</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>systemd-pstore.service</refentrytitle>
  16     <manvolnum>8</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>systemd-pstore.service</refname>
  21     <refname>systemd-pstore</refname>
  22     <refpurpose>A service to archive contents of pstore</refpurpose>
  23   </refnamediv>
  24
  25   <refsynopsisdiv>
  26     <para><filename>/usr/lib/systemd/systemd-pstore</filename></para>
  27     <para><filename>systemd-pstore.service</filename></para>
  28   </refsynopsisdiv>
  29
  30   <refsect1>
  31     <title>Description</title>
  32     <para><filename>systemd-pstore.service</filename> is a system service that archives the
  33     contents of the Linux persistent storage filesystem, pstore, to other storage,
  34     thus preserving the existing information contained in the pstore, and clearing
  35     pstore storage for future error events.</para>
  36
  37     <para>Linux provides a persistent storage file system, pstore, that can store
  38     error records when the kernel dies (or reboots or powers-off). These records in
  39     turn can be referenced to debug kernel problems (currently the kernel stuffs
  40     the tail of the dmesg, which also contains a stack backtrace, into pstore).</para>
  41
  42     <para>The pstore file system supports a variety of backends that map onto persistent
  43     storage, such as the ACPI ERST and UEFI variables. The pstore backends
  44     typically offer a relatively small amount of persistent storage, e.g. 64KiB,
  45     which can quickly fill up and thus prevent subsequent kernel crashes from
  46     recording errors. Thus there is a need to monitor and extract the pstore
  47     contents so that future kernel problems can also record information in the
  48     pstore.</para>
  49
  50     <para>The pstore service is independent of the kdump service. In cloud environments
  51     specifically, host and guest filesystems are on remote filesystems (eg. iSCSI
  52     or NFS), thus kdump relies (implicitly and/or explicitly) upon proper operation
  53     of networking software *and* hardware *and* infrastructure. Thus it may not be
  54     possible to capture a kernel coredump to a file since writes over the network
  55     may not be possible.</para>
  56
  57     <para>The pstore backend, on the other hand, is completely local and provides a path
  58     to store error records which will survive a reboot and aid in post-mortem
  59     debugging.</para>
  60
  61     <para>The <command>systemd-pstore</command> executable does the actual work. Upon starting,
  62     the <filename>pstore.conf</filename> file is read and the <filename>/sys/fs/pstore</filename>
  63     directory contents are processed according to the options. Pstore files are written to the
  64     journal, and optionally saved into <filename>/var/lib/systemd/pstore</filename>.</para>
  65   </refsect1>
  66
  67   <refsect1>
  68     <title>Configuration</title>
  69
  70     <para>The behavior of <command>systemd-pstore</command> is configured through the configuration file
  71     <filename>/etc/systemd/pstore.conf</filename> and corresponding snippets
  72     <filename>/etc/systemd/pstore.conf.d/*.conf</filename>, see
  73     <citerefentry><refentrytitle>pstore.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
  74     </para>
  75
  76     <refsect2>
  77       <title>Disabling pstore processing</title>
  78
  79       <para>To disable pstore processing by <command>systemd-pstore</command>,
  80       set <programlisting>Storage=none</programlisting> in
  81       <citerefentry><refentrytitle>pstore.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
  82       </para>
  83     </refsect2>
  84   </refsect1>
  85
  86   <refsect1>
  87     <title>Usage</title>
  88     <para>Data stored in the journal can be viewed with
  89     <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  90     as usual.</para>
  91   </refsect1>
  92
  93   <refsect1>
  94     <title>See Also</title>
  95     <para>
  96       <citerefentry><refentrytitle>pstore.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  97     </para>
  98   </refsect1>
  99 </refentry>