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514094f9 | 1 | <?xml version='1.0'?> |
5146e7e8 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
9 | <refentry id="systemd-coredump" conditional='ENABLE_COREDUMP' | |
10 | xmlns:xi="http://www.w3.org/2001/XInclude"> | |
11 | ||
12 | <refentryinfo> | |
13 | <title>systemd-coredump</title> | |
14 | <productname>systemd</productname> | |
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15 | </refentryinfo> |
16 | ||
17 | <refmeta> | |
18 | <refentrytitle>systemd-coredump</refentrytitle> | |
19 | <manvolnum>8</manvolnum> | |
20 | </refmeta> | |
21 | ||
22 | <refnamediv> | |
23 | <refname>systemd-coredump</refname> | |
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24 | <refname>systemd-coredump.socket</refname> |
25 | <refname>systemd-coredump@.service</refname> | |
246ba4aa | 26 | <refpurpose>Acquire, save and process core dumps</refpurpose> |
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27 | </refnamediv> |
28 | ||
29 | <refsynopsisdiv> | |
12b42c76 | 30 | <para><filename>/usr/lib/systemd/systemd-coredump</filename></para> |
f6940bc3 | 31 | <para><filename>/usr/lib/systemd/systemd-coredump</filename> <option>--backtrace</option></para> |
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32 | <para><filename>systemd-coredump@.service</filename></para> |
33 | <para><filename>systemd-coredump.socket</filename></para> | |
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34 | </refsynopsisdiv> |
35 | ||
36 | <refsect1> | |
37 | <title>Description</title> | |
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38 | <para><filename>systemd-coredump@.service</filename> is a system service that can acquire core |
39 | dumps from the kernel and handle them in various ways. The <command>systemd-coredump</command> | |
40 | executable does the actual work. It is invoked twice: once as the handler by the kernel, and the | |
41 | second time in the <filename>systemd-coredump@.service</filename> to actually write the data to | |
42 | the journal.</para> | |
43 | ||
44 | <para>When the kernel invokes <command>systemd-coredump</command> to handle a core dump, it runs | |
45 | in privileged mode, and will connect to the socket created by the | |
46 | <filename>systemd-coredump.socket</filename> unit, which in turn will spawn an unprivileged | |
47 | <filename>systemd-coredump@.service</filename> instance to process the core dump. Hence | |
48 | <filename>systemd-coredump.socket</filename> and <filename>systemd-coredump@.service</filename> | |
49 | are helper units which do the actual processing of core dumps and are subject to normal service | |
50 | management.</para> | |
5146e7e8 | 51 | |
246ba4aa PM |
52 | <para>Core dumps can be written to the journal or saved as a file. Once saved they can be retrieved |
53 | for further processing, for example in | |
54 | <citerefentry project='man-pages'><refentrytitle>gdb</refentrytitle><manvolnum>1</manvolnum></citerefentry>. | |
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55 | </para> |
56 | ||
246ba4aa PM |
57 | <para>By default, <command>systemd-coredump</command> will log the core dump including a backtrace |
58 | if possible to the journal and store the core dump itself in an external file in | |
59 | <filename>/var/lib/systemd/coredump</filename>.</para> | |
5146e7e8 | 60 | |
246ba4aa PM |
61 | <para>The behavior of a specific program upon reception of a signal is governed by a few |
62 | factors which are described in detail in | |
63 | <citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry>. | |
64 | In particular, the core dump will only be processed when the related resource limits are sufficient. | |
f3962329 | 65 | </para> |
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66 | |
67 | <para>It is also possible to invoke <command>systemd-coredump</command> with | |
68 | <option>--backtrace</option> option. In this case, <command>systemd-coredump</command> expects | |
69 | a journal entry in the journal | |
28a0ad81 | 70 | <ulink url="https://www.freedesktop.org/wiki/Software/systemd/export">Journal Export Format</ulink> |
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71 | on standard input. The entry should contain a <varname>MESSAGE=</varname> field and any additional |
72 | metadata fields the caller deems reasonable. <command>systemd-coredump</command> will append | |
73 | additional metadata fields in the same way it does for core dumps received from the kernel. In | |
74 | this mode, no core dump is stored in the journal.</para> | |
246ba4aa | 75 | </refsect1> |
7382a3cc | 76 | |
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77 | <refsect1> |
78 | <title>Configuration</title> | |
79 | <para>For programs started by <command>systemd</command> process resource limits can be set by directive | |
80 | <varname>LimitCore=</varname>, see | |
81 | <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>. | |
82 | </para> | |
83 | ||
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84 | <para>In order to be used by the kernel to handle core dumps, |
85 | <command>systemd-coredump</command> must be configured in | |
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86 | <citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
87 | parameter <varname>kernel.core_pattern</varname>. The syntax of this parameter is explained in | |
88 | <citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry>. | |
f95b0be7 | 89 | systemd installs the file <filename>/usr/lib/sysctl.d/50-coredump.conf</filename> which configures |
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90 | <varname>kernel.core_pattern</varname> accordingly. This file may be masked or overridden to use a different |
91 | setting following normal | |
92 | <citerefentry><refentrytitle>sysctl.d</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
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93 | rules. If the sysctl configuration is modified, it must be updated in the kernel before it |
94 | takes effect, see | |
246ba4aa | 95 | <citerefentry project='man-pages'><refentrytitle>sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
7382a3cc | 96 | and |
246ba4aa | 97 | <citerefentry><refentrytitle>systemd-sysctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>. |
7382a3cc | 98 | </para> |
246ba4aa | 99 | |
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100 | <para>In order to by used in the <option>--backtrace</option> mode, an appropriate backtrace |
101 | handler must be installed on the sender side. For example, in case of | |
98e9d710 | 102 | <citerefentry project='die-net'><refentrytitle>python</refentrytitle><manvolnum>1</manvolnum></citerefentry>, this |
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103 | means a <varname>sys.excepthook</varname> must installed, see |
104 | <ulink url="https://github.com/keszybz/systemd-coredump-python">systemd-coredump-python</ulink>. | |
105 | </para> | |
106 | ||
2dd67817 | 107 | <para>The behavior of <command>systemd-coredump</command> itself is configured through the configuration file |
246ba4aa PM |
108 | <filename>/etc/systemd/coredump.conf</filename> and corresponding snippets |
109 | <filename>/etc/systemd/coredump.conf.d/*.conf</filename>, see | |
110 | <citerefentry><refentrytitle>coredump.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>. A new | |
111 | instance of <command>systemd-coredump</command> is invoked upon receiving every core dump. Therefore, changes | |
112 | in these files will take effect the next time a core dump is received.</para> | |
113 | ||
114 | <para>Resources used by core dump files are restricted in two ways. Parameters like maximum size of acquired | |
115 | core dumps and files can be set in files <filename>/etc/systemd/coredump.conf</filename> and snippets mentioned | |
116 | above. In addition the storage time of core dump files is restricted by <command>systemd-tmpfiles</command>, | |
117 | corresponding settings are by default in <filename>/usr/lib/tmpfiles.d/systemd.conf</filename>.</para> | |
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118 | |
119 | <refsect2> | |
120 | <title>Disabling coredump processing</title> | |
121 | ||
122 | <para>To disable potentially resource-intensive processing by <command>systemd-coredump</command>, | |
123 | set <programlisting>Storage=none | |
124 | ProcessSizeMax=0</programlisting> in | |
125 | <citerefentry><refentrytitle>coredump.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>. | |
126 | </para> | |
127 | </refsect2> | |
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128 | </refsect1> |
129 | ||
130 | <refsect1> | |
131 | <title>Usage</title> | |
132 | <para>Data stored in the journal can be viewed with | |
133 | <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
134 | as usual. | |
135 | <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> | |
136 | can be used to retrieve saved core dumps independent of their location, to display information and to process | |
137 | them e.g. by passing to the GNU debugger (gdb).</para> | |
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138 | </refsect1> |
139 | ||
140 | <refsect1> | |
141 | <title>See Also</title> | |
142 | <para> | |
143 | <citerefentry><refentrytitle>coredump.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
144 | <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
145 | <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
246ba4aa | 146 | <citerefentry><refentrytitle>systemd-tmpfiles</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
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147 | <citerefentry project='man-pages'><refentrytitle>core</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
148 | <citerefentry><refentrytitle>sysctl.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
149 | <citerefentry><refentrytitle>systemd-sysctl.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>. | |
150 | </para> | |
151 | </refsect1> | |
152 | </refentry> |