<title>Description</title>
<para>Unit configuration files for services, sockets,
- mount points and swap devices share a subset of
+ mount points, and swap devices share a subset of
configuration options which define the execution
environment of spawned processes.</para>
configuration options are configured in the [Service],
[Socket], [Mount], or [Swap] sections, depending on the unit
type.</para>
-
- <para>Processes started by the system systemd instance
- are executed in a clean environment in which only the
- <varname>$PATH</varname> and <varname>$LANG</varname>
- variables are set by default. In order to add
- additional variables, see the
- <varname>Environment=</varname> and
- <varname>EnvironmentFile=</varname> options below. To
- specify variables globally, see
- <varname>DefaultEnvironment=</varname> in
- <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
- or the kernel option
- <varname>systemd.setenv=</varname> in
- <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>. Processes
- started by the user systemd instances inherit all
- environment variables from the user systemd instance,
- and have <varname>$HOME</varname>,
- <varname>$USER</varname>,
- <varname>$XDG_RUNTIME_DIR</varname> defined, among
- others. In addition, <varname>$MANAGERPID</varname>
- contains the PID of the user systemd instance.</para>
</refsect1>
<refsect1>
for the assignment.</para>
<para>Example:
- <programlisting>Environment="VAR1=word1 word2" VAR2=word3 "VAR3=word 5 6"</programlisting>
+ <programlisting>Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"</programlisting>
gives three variables <literal>VAR1</literal>,
- <literal>VAR2</literal>, <literal>VAR3</literal>.
+ <literal>VAR2</literal>, <literal>VAR3</literal>
+ with the values <literal>word1 word2</literal>,
+ <literal>word3</literal>, <literal>$word 5 6</literal>.
</para>
<para>
system namespace for the executed
processes and mounts private
<filename>/tmp</filename> and
- <filename>/var/tmp</filename> directories
- inside it, that are not shared by
- processes outside of the
+ <filename>/var/tmp</filename>
+ directories inside it that is not
+ shared by processes outside of the
namespace. This is useful to secure
access to temporary files of the
process, but makes sharing between
<filename>/tmp</filename> or
<filename>/var/tmp</filename>
impossible. All temporary data created
- by service will be removed after service
- is stopped. Defaults to
- false.</para></listitem>
+ by service will be removed after
+ the service is stopped. Defaults to
+ false. Note that it is possible to run
+ two or more units within the same
+ private <filename>/tmp</filename> and
+ <filename>/var/tmp</filename>
+ namespace by using the
+ <varname>JoinsNamespaceOf=</varname>
+ directive, see
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for details.</para></listitem>
</varlistentry>
<varlistentry>
available to the executed process.
This is useful to securely turn off
network access by the executed
+ process. Defaults to false. Note that
+ it is possible to run two or more
+ units within the same private network
+ namespace by using the
+ <varname>JoinsNamespaceOf=</varname>
+ directive, see
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for details.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>PrivateDevices=</varname></term>
+
+ <listitem><para>Takes a boolean
+ argument. If true, sets up a new /dev
+ namespace for the executed processes
+ and only adds API pseudo devices such
+ as <filename>/dev/null</filename>,
+ <filename>/dev/zero</filename> or
+ <filename>/dev/random</filename> to
+ it, but no physical devices such as
+ <filename>/dev/sda</filename>. This is
+ useful to securely turn off physical
+ device access by the executed
process. Defaults to
false.</para></listitem>
</varlistentry>
this service.</para></listitem>
</varlistentry>
+ <varlistentry>
+ <term><varname>SELinuxContext=</varname></term>
+
+ <listitem><para>Set the SELinux
+ security context of the executed
+ process. If set, this will override
+ the automated domain
+ transition. However, the policy still
+ needs to autorize the transition. This
+ directive is ignored if SELinux is
+ disabled. If prefixed by
+ <literal>-</literal>, all errors will
+ be ignored. See
+ <citerefentry><refentrytitle>setexeccon</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ for details.</para></listitem>
+ </varlistentry>
+
<varlistentry>
<term><varname>IgnoreSIGPIPE=</varname></term>
</variablelist>
</refsect1>
+ <refsect1>
+ <title>Environment variables in spawned processes</title>
+
+ <para>Processes started by the system are executed in
+ a clean environment in which select variables
+ listed below are set. System processes started by systemd
+ do not inherit variables from PID 1, but processes
+ started by user systemd instances inherit all
+ environment variables from the user systemd instance.
+ </para>
+
+ <variablelist class='environment-variables'>
+ <varlistentry>
+ <term><varname>$PATH</varname></term>
+
+ <listitem><para>Colon-separated list
+ of directiories to use when launching
+ executables. Systemd uses a fixed
+ value of
+ <filename>/usr/local/sbin</filename>:<filename>/usr/local/bin</filename>:<filename>/usr/sbin</filename>:<filename>/usr/bin</filename>:<filename>/sbin</filename>:<filename>/bin</filename>.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$LANG</varname></term>
+
+ <listitem><para>Locale. Can be set in
+ <citerefentry><refentrytitle>locale.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ or on the kernel command line (see
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ and
+ <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>).
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$USER</varname></term>
+ <term><varname>$LOGNAME</varname></term>
+ <term><varname>$HOME</varname></term>
+ <term><varname>$SHELL</varname></term>
+
+ <listitem><para>User name (twice), home
+ directory, and the login shell.
+ The variables are set for the units that
+ have <varname>User=</varname> set,
+ which includes user
+ <command>systemd</command> instances.
+ See
+ <citerefentry><refentrytitle>passwd</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$XDG_RUNTIME_DIR</varname></term>
+
+ <listitem><para>The directory for volatile
+ state. Set for the user <command>systemd</command>
+ instance, and also in user sessions.
+ See
+ <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$XDG_SESSION_ID</varname></term>
+ <term><varname>$XDG_SEAT</varname></term>
+ <term><varname>$XDG_VTNR</varname></term>
+
+ <listitem><para>The identifier of the
+ session, the seat name, and
+ virtual terminal of the session. Set
+ by
+ <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ for login sessions.
+ <varname>$XDG_SEAT</varname> and
+ <varname>$XDG_VTNR</varname> will
+ only be set when attached to a seat and a
+ tty.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$MANAGERPID</varname></term>
+
+ <listitem><para>The PID of the user
+ <command>systemd</command> instance,
+ set for processes spawned by it.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$LISTEN_FDS</varname></term>
+ <term><varname>$LISTEN_PID</varname></term>
+
+ <listitem><para>Information about file
+ descriptors passed to a service for
+ socket activation. See
+ <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>$TERM</varname></term>
+
+ <listitem><para>Terminal type, set
+ only for units connected to a terminal
+ (<varname>StandardInput=tty</varname>,
+ <varname>StandardOutput=tty</varname>,
+ or
+ <varname>StandardError=tty</varname>).
+ See
+ <citerefentry><refentrytitle>termcap</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ </para></listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para>Additional variables may be configured by the
+ following means: for processes spawned in specific
+ units, use the <varname>Environment=</varname> and
+ <varname>EnvironmentFile=</varname> options above; to
+ specify variables globally, use
+ <varname>DefaultEnvironment=</varname> (see
+ <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
+ or the kernel option
+ <varname>systemd.setenv=</varname> (see
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>). Additional
+ variables may also be set through PAM,
+ c.f. <citerefentry><refentrytitle>pam_env</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
+ </refsect1>
+
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.cgroup</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+ <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>exec</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
~ianmdlvl / elogind.git / blobdiff