man: document image policy syntax and semantics, and the hooks in the various components

[thirdparty/systemd.git] / man / systemd-tmpfiles.xml

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<!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-tmpfiles"
    xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>systemd-tmpfiles</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>systemd-tmpfiles</refentrytitle>
    <manvolnum>8</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemd-tmpfiles</refname>
    <refname>systemd-tmpfiles-setup.service</refname>
    <refname>systemd-tmpfiles-setup-dev.service</refname>
    <refname>systemd-tmpfiles-clean.service</refname>
    <refname>systemd-tmpfiles-clean.timer</refname>
    <refpurpose>Creates, deletes and cleans up volatile
    and temporary files and directories</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis>
      <command>systemd-tmpfiles</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="opt" rep="repeat"><replaceable>CONFIGFILE</replaceable></arg>
    </cmdsynopsis>

    <para>System units:
<literallayout><filename>systemd-tmpfiles-setup.service</filename>
<filename>systemd-tmpfiles-setup-dev.service</filename>
<filename>systemd-tmpfiles-clean.service</filename>
<filename>systemd-tmpfiles-clean.timer</filename></literallayout></para>

    <para>User units:
<literallayout><filename>systemd-tmpfiles-setup.service</filename>
<filename>systemd-tmpfiles-clean.service</filename>
<filename>systemd-tmpfiles-clean.timer</filename></literallayout></para>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><command>systemd-tmpfiles</command> creates, deletes, and cleans up volatile and temporary files
    and directories, using the configuration file format and location specified in
    <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>. It must
    be invoked with one or more options <option>--create</option>, <option>--remove</option>, and
    <option>--clean</option>, to select the respective subset of operations.</para>

    <para>By default, directives from all configuration files are applied. When invoked with
    <option>--replace=<replaceable>PATH</replaceable></option>, arguments specified on the command line are
    used instead of the configuration file <replaceable>PATH</replaceable>. Otherwise, if one or more
    absolute filenames are passed on the command line, only the directives in these files are applied. If
    <literal>-</literal> is specified instead of a filename, directives are read from standard input. If only
    the basename of a configuration file is specified, all configuration directories as specified in
    <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry> are
    searched for a matching file and the file found that has the highest priority is executed.</para>

    <para>System services (<filename>systemd-tmpfiles-setup.service</filename>,
    <filename>systemd-tmpfiles-setup-dev.service</filename>,
    <filename>systemd-tmpfiles-clean.service</filename>) invoke <command>systemd-tmpfiles</command> to create
    system files and to perform system wide cleanup. Those services read administrator-controlled
    configuration files in <filename>tmpfiles.d/</filename> directories. User services
    (<filename>systemd-tmpfiles-setup.service</filename>,
    <filename>systemd-tmpfiles-clean.service</filename>) also invoke <command>systemd-tmpfiles</command>, but
    it reads a separate set of files, which includes user-controlled files under
    <filename>~/.config/user-tmpfiles.d/</filename> and <filename>~/.local/share/user-tmpfiles.d/</filename>,
    and administrator-controlled files under <filename>/usr/share/user-tmpfiles.d/</filename>. Users may use
    this to create and clean up files under their control, but the system instance performs global cleanup
    and is not influenced by user configuration. Note that this means a time-based cleanup configured in the
    system instance, such as the one typically configured for <filename>/tmp/</filename>, will thus also
    affect files created by the user instance if they are placed in <filename>/tmp/</filename>, even if the
    user instance's time-based cleanup is turned off.</para>

    <para>To re-apply settings after configuration has been modified, simply restart
    <filename>systemd-tmpfiles-clean.service</filename>, which will apply any settings which can be safely
    executed at runtime. To debug <command>systemd-tmpfiles</command>, it may be useful to invoke it
    directly from the command line with increased log level (see <varname>$SYSTEMD_LOG_LEVEL</varname>
    below).</para>
  </refsect1>

  <refsect1>
    <title>Options</title>

    <para>The following options are understood:</para>

    <variablelist>
      <varlistentry>
        <term><option>--create</option></term>
        <listitem><para>If this option is passed, all files and
        directories marked with
        <varname>f</varname>,
        <varname>F</varname>,
        <varname>w</varname>,
        <varname>d</varname>,
        <varname>D</varname>,
        <varname>v</varname>,
        <varname>p</varname>,
        <varname>L</varname>,
        <varname>c</varname>,
        <varname>b</varname>,
        <varname>m</varname>
        in the configuration files are created or written to. Files
        and directories marked with
        <varname>z</varname>,
        <varname>Z</varname>,
        <varname>t</varname>,
        <varname>T</varname>,
        <varname>a</varname>, and
        <varname>A</varname> have their ownership, access mode and
        security labels set.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--clean</option></term>
        <listitem><para>If this option is passed, all files and
        directories with an age parameter configured will be cleaned
        up.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--remove</option></term>
        <listitem><para>If this option is passed, the contents of
        directories marked with <varname>D</varname> or
        <varname>R</varname>, and files or directories themselves
        marked with <varname>r</varname> or <varname>R</varname> are
        removed unless an exclusive or shared BSD lock is taken on them (see <citerefentry
        project='man-pages'><refentrytitle>flock</refentrytitle><manvolnum>2</manvolnum></citerefentry>).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--user</option></term>
        <listitem><para>Execute "user" configuration, i.e. <filename>tmpfiles.d</filename>
        files in user configuration directories.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--boot</option></term>
        <listitem><para>Also execute lines with an exclamation mark.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--prefix=<replaceable>path</replaceable></option></term>
        <listitem><para>Only apply rules with paths that start with
        the specified prefix. This option can be specified multiple
        times.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--exclude-prefix=<replaceable>path</replaceable></option></term>
        <listitem><para>Ignore rules with paths that start with the
        specified prefix. This option can be specified multiple
        times.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-E</option></term>
        <listitem><para>A shortcut for <literal>--exclude-prefix=/dev --exclude-prefix=/proc
        --exclude-prefix=/run --exclude-prefix=/sys</literal>, i.e. exclude the hierarchies typically backed
        by virtual or memory file systems. This is useful in combination with <option>--root=</option>, if
        the specified directory tree contains an OS tree without these virtual/memory file systems mounted
        in, as it is typically not desirable to create any files and directories below these subdirectories
        if they are supposed to be overmounted during runtime.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--root=<replaceable>root</replaceable></option></term>
        <listitem><para>Takes a directory path as an argument. All paths will be prefixed with the given alternate
        <replaceable>root</replaceable> path, including config search paths.</para>

        <para>When this option is used, the libc Name Service Switch (NSS) is bypassed for resolving users
        and groups. Instead the files <filename>/etc/passwd</filename> and <filename>/etc/group</filename>
        inside the alternate root are read directly. This means that users/groups not listed in these files
        will not be resolved, i.e. LDAP NIS and other complex databases are not considered.</para>

        <para>Consider combining this with <option>-E</option> to ensure the invocation does not create files
        or directories below mount points in the OS image operated on that are typically overmounted during
        runtime.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--image=<replaceable>image</replaceable></option></term>

        <listitem><para>Takes a path to a disk image file or block device node. If specified all operations
        are applied to file system in the indicated disk image. This is similar to <option>--root=</option>
        but operates on file systems stored in disk images or block devices. The disk image should either
        contain just a file system or a set of file systems within a GPT partition table, following the
        <ulink url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">Discoverable Partitions
        Specification</ulink>. For further information on supported disk images, see
        <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
        switch of the same name.</para>

        <para>Implies <option>-E</option>.</para></listitem>
      </varlistentry>

      <xi:include href="standard-options.xml" xpointer="image-policy-open" />

      <varlistentry>
        <term><option>--replace=<replaceable>PATH</replaceable></option></term>
        <listitem><para>When this option is given, one or more positional arguments
        must be specified. All configuration files found in the directories listed in
        <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        will be read, and the configuration given on the command line will be
        handled instead of and with the same priority as the configuration file
        <replaceable>PATH</replaceable>.</para>

        <para>This option is intended to be used when package installation scripts
        are running and files belonging to that package are not yet available on
        disk, so their contents must be given on the command line, but the admin
        configuration might already exist and should be given higher priority.
        </para></listitem>
      </varlistentry>

      <xi:include href="standard-options.xml" xpointer="cat-config" />
      <xi:include href="standard-options.xml" xpointer="no-pager" />
      <xi:include href="standard-options.xml" xpointer="help" />
      <xi:include href="standard-options.xml" xpointer="version" />
    </variablelist>

    <para>It is possible to combine <option>--create</option>, <option>--clean</option>, and <option>--remove</option>
    in one invocation (in which case removal and cleanup are executed before creation of new files). For example,
    during boot the following command line is executed to ensure that all temporary and volatile directories are
    removed and created according to the configuration file:</para>

    <programlisting>systemd-tmpfiles --remove --create</programlisting>
  </refsect1>

  <refsect1>
    <title>Credentials</title>

    <para><command>systemd-tmpfiles</command> supports the service credentials logic as implemented by
    <varname>LoadCredential=</varname>/<varname>SetCredential=</varname> (see
    <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
    details). The following credentials are used when passed in:</para>

    <variablelist>
      <varlistentry>
        <term><literal>tmpfiles.extra</literal></term>

        <listitem><para> The contents of this credential may contain additional lines to operate on. The
        credential contents should follow the same format as any other <filename>tmpfiles.d/</filename>
        drop-in configuration file. If this credential is passed it is processed after all of the drop-in
        files read from the file system. The lines in the credential can hence augment existing lines of the
        OS, but not override them.</para></listitem>
      </varlistentry>
    </variablelist>

    <para>Note that by default the <filename>systemd-tmpfiles-setup.service</filename> unit file (and related
    unit files) is set up to inherit the <literal>tmpfiles.extra</literal> credential from the service
    manager.</para>
  </refsect1>

  <refsect1>
    <title>Environment</title>

    <variablelist class='environment-variables'>
      <xi:include href="common-variables.xml" xpointer="log-level" />
      <xi:include href="common-variables.xml" xpointer="log-color" />
      <xi:include href="common-variables.xml" xpointer="log-time" />
      <xi:include href="common-variables.xml" xpointer="log-location" />
      <xi:include href="common-variables.xml" xpointer="log-target" />
      <xi:include href="common-variables.xml" xpointer="pager" />
      <xi:include href="common-variables.xml" xpointer="less" />
      <xi:include href="common-variables.xml" xpointer="lesscharset" />
      <xi:include href="common-variables.xml" xpointer="lesssecure" />
      <xi:include href="common-variables.xml" xpointer="colors" />
      <xi:include href="common-variables.xml" xpointer="urlify" />
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Unprivileged --cleanup operation</title>

    <para><command>systemd-tmpfiles</command> tries to avoid changing
    the access and modification times on the directories it accesses,
    which requires <constant>CAP_FOWNER</constant> privileges. When
    running as non-root, directories which are checked for files to
    clean up will have their access time bumped, which might prevent
    their cleanup.
    </para>
  </refsect1>

  <refsect1>
    <title>Exit status</title>

    <para>On success, 0 is returned. If the configuration was syntactically invalid (syntax errors, missing
    arguments, …), so some lines had to be ignored, but no other errors occurred, <constant>65</constant> is
    returned (<constant>EX_DATAERR</constant> from <filename>/usr/include/sysexits.h</filename>). If the
    configuration was syntactically valid, but could not be executed (lack of permissions, creation of files
    in missing directories, invalid contents when writing to <filename>/sys/</filename> values, …),
    <constant>73</constant> is returned (<constant>EX_CANTCREAT</constant> from
    <filename>/usr/include/sysexits.h</filename>). Otherwise, <constant>1</constant> is returned
    (<constant>EXIT_FAILURE</constant> from <filename>/usr/include/stdlib.h</filename>).</para>

    <para>Note: when creating items, if the target already exists, but is of the wrong type or otherwise does
    not match the requested state, and forced operation has not been requested with <literal>+</literal>,
    a message is emitted, but the failure is otherwise ignored.</para>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>