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Copyright 2010 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 2 of the License, or
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
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WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- General Public License for more details.
+ Lesser General Public License for more details.
- You should have received a copy of the GNU General Public License
+ You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refnamediv>
<refname>systemd.exec</refname>
- <refpurpose>systemd execution environment configuration</refpurpose>
+ <refpurpose>Execution environment configuration</refpurpose>
</refnamediv>
<refsynopsisdiv>
- <para><filename>systemd.service</filename>,
- <filename>systemd.socket</filename>,
- <filename>systemd.mount</filename></para>
+ <para><filename><replaceable>service</replaceable>.service</filename>,
+ <filename><replaceable>socket</replaceable>.socket</filename>,
+ <filename><replaceable>mount</replaceable>.mount</filename>,
+ <filename><replaceable>swap</replaceable>.swap</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
- <para>Unit configuration files for services, sockets
- and mount points share a subset of configuration
- options which define the execution environment of
- spawned processes.</para>
+ <para>Unit configuration files for services, sockets,
+ mount points, and swap devices share a subset of
+ configuration options which define the execution
+ environment of spawned processes.</para>
<para>This man page lists the configuration options
- shared by these three unit types. See
+ shared by these four unit types. See
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for the common options of all unit configuration
files, and
- <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
and
<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for more information on the specific unit
configuration files. The execution specific
configuration options are configured in the [Service],
- [Socket] resp. [Mount] section, depending on the unit
+ [Socket], [Mount], or [Swap] sections, depending on the unit
type.</para>
</refsect1>
<refsect1>
<title>Options</title>
- <variablelist>
+ <variablelist class='unit-directives'>
<varlistentry>
<term><varname>WorkingDirectory=</varname></term>
<listitem><para>Takes an absolute
directory path. Sets the working
- directory for executed
- processes.</para></listitem>
+ directory for executed processes. If
+ not set, defaults to the root directory
+ when systemd is running as a system
+ instance and the respective user's
+ home directory if run as
+ user.</para></listitem>
</varlistentry>
<varlistentry>
directory for executed processes, with
the
<citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>2</manvolnum></citerefentry>
- system call. If this is used it must
+ system call. If this is used, it must
be ensured that the process and all
its auxiliary files are available in
the <function>chroot()</function>
<term><varname>Group=</varname></term>
<listitem><para>Sets the Unix user
- resp. group the processes are executed
- as. Takes a single user resp. group
+ or group that the processes are executed
+ as, respectively. Takes a single user or group
name or ID as argument. If no group is
- set the default group of the user is
+ set, the default group of the user is
chosen.</para></listitem>
</varlistentry>
<listitem><para>Sets the supplementary
Unix groups the processes are executed
- as. This takes a space seperated list
+ as. This takes a space-separated list
of group names or IDs. This option may
be specified more than once in which
case all listed groups are set as
- supplementary groups. This option does
- not override but extend the list of
- supplementary groups configured in the
- system group database for the
+ supplementary groups. When the empty
+ string is assigned the list of
+ supplementary groups is reset, and all
+ assignments prior to this one will
+ have no effect. In any way, this
+ option does not override, but extends
+ the list of supplementary groups
+ configured in the system group
+ database for the
user.</para></listitem>
</varlistentry>
</varlistentry>
<varlistentry>
- <term><varname>OOMAdjust=</varname></term>
+ <term><varname>OOMScoreAdjust=</varname></term>
<listitem><para>Sets the adjustment
level for the Out-Of-Memory killer for
executed processes. Takes an integer
- between -17 (to disable OOM killing
- for this process) and 15 (to make
+ between -1000 (to disable OOM killing
+ for this process) and 1000 (to make
killing of this process under memory
pressure very likely). See <ulink
- url="http://www.kernel.org/doc/Documentation/filesystems/proc.txt">proc.txt</ulink>
+ url="https://www.kernel.org/doc/Documentation/filesystems/proc.txt">proc.txt</ulink>
for details.</para></listitem>
</varlistentry>
<listitem><para>Sets the CPU
scheduling priority for executed
- processes. Takes an integer between 1
- (lowest priority) and 99 (highest
- priority). The available priority
+ processes. The available priority
range depends on the selected CPU
- scheduling policy (see above). See
- <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
- for details.</para></listitem>
+ scheduling policy (see above). For
+ real-time scheduling policies an
+ integer between 1 (lowest priority)
+ and 99 (highest priority) can be used.
+ See <citerefentry><refentrytitle>sched_setscheduler</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ for details.
+ </para></listitem>
</varlistentry>
<varlistentry>
<term><varname>CPUSchedulingResetOnFork=</varname></term>
<listitem><para>Takes a boolean
- argument. If true elevated CPU
+ argument. If true, elevated CPU
scheduling priorities and policies
will be reset when the executed
processes fork, and can hence not leak
<listitem><para>Controls the CPU
affinity of the executed
- processes. Takes a space-seperated
- list of CPU indexes. See
+ processes. Takes a space-separated
+ list of CPU indexes. This option may
+ be specified more than once in which
+ case the specificed CPU affinity masks
+ are merged. If the empty string is
+ assigned, the mask is reset, all
+ assignments prior to this will have no
+ effect. See
<citerefentry><refentrytitle>sched_setaffinity</refentrytitle><manvolnum>2</manvolnum></citerefentry>
for details.</para></listitem>
</varlistentry>
octal notation. See
<citerefentry><refentrytitle>umask</refentrytitle><manvolnum>2</manvolnum></citerefentry>
for details. Defaults to
- 0002.</para></listitem>
+ 0022.</para></listitem>
</varlistentry>
<varlistentry>
<listitem><para>Sets environment
variables for executed
- processes. Takes a space-seperated
+ processes. Takes a space-separated
list of variable assignments. This
option may be specified more than once
in which case all listed variables
will be set. If the same variable is
- set twice the later setting will
- override the earlier setting. See
+ set twice, the later setting will
+ override the earlier setting. If the
+ empty string is assigned to this
+ option, the list of environment
+ variables is reset, all prior
+ assignments have no effect.
+ Variable expansion is not performed
+ inside the strings, however, specifier
+ expansion is possible. The $ character has
+ no special meaning.
+ If you need to assign a value containing spaces
+ to a variable, use double quotes (")
+ for the assignment.</para>
+
+ <para>Example:
+ <programlisting>Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"</programlisting>
+ gives three variables <literal>VAR1</literal>,
+ <literal>VAR2</literal>, <literal>VAR3</literal>
+ with the values <literal>word1 word2</literal>,
+ <literal>word3</literal>, <literal>$word 5 6</literal>.
+ </para>
+
+ <para>
+ See
<citerefentry><refentrytitle>environ</refentrytitle><manvolnum>7</manvolnum></citerefentry>
- for details.</para></listitem>
+ for details about environment variables.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>EnvironmentFile=</varname></term>
<varname>Environment=</varname> but
reads the environment variables from a
text file. The text file should
- contain new-line seperated variable
+ contain new-line-separated variable
assignments. Empty lines and lines
starting with ; or # will be ignored,
- which may be used for
- commenting.</para></listitem>
+ which may be used for commenting. A line
+ ending with a backslash will be concatenated
+ with the following one, allowing multiline variable
+ definitions. The parser strips leading
+ and trailing whitespace from the values
+ of assignments, unless you use
+ double quotes (").</para>
+
+ <para>The argument passed should be an
+ absolute filename or wildcard
+ expression, optionally prefixed with
+ <literal>-</literal>, which indicates
+ that if the file does not exist, it
+ will not be read and no error or warning
+ message is logged. This option may be
+ specified more than once in which case
+ all specified files are read. If the
+ empty string is assigned to this
+ option, the list of file to read is
+ reset, all prior assignments have no
+ effect.</para>
+
+ <para>The files listed with this
+ directive will be read shortly before
+ the process is executed. Settings from
+ these files override settings made
+ with
+ <varname>Environment=</varname>. If
+ the same variable is set twice from
+ these files, the files will be read in
+ the order they are specified and the
+ later setting will override the
+ earlier setting.</para></listitem>
</varlistentry>
<varlistentry>
<option>tty-force</option>,
<option>tty-fail</option> or
<option>socket</option>. If
- <option>null</option> is selected
+ <option>null</option> is selected,
standard input will be connected to
<filename>/dev/null</filename>,
i.e. all read attempts by the process
will result in immediate EOF. If
- <option>tty</option> is selected
+ <option>tty</option> is selected,
standard input is connected to a TTY
(as configured by
<varname>TTYPath=</varname>, see
below) and the executed process
becomes the controlling process of the
terminal. If the terminal is already
- being controlled by another process it
- is waited until that process releases
- the
- terminal. <option>tty-force</option>
+ being controlled by another process, the
+ executed process waits until the current
+ controlling process releases the
+ terminal.
+ <option>tty-force</option>
is similar to <option>tty</option>,
but the executed process is forcefully
and immediately made the controlling
file (see
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for details) specifies a single socket
- only. If this option is set standard
+ only. If this option is set, standard
input will be connected to the socket
the service was activated from, which
is primarily useful for compatibility
<option>null</option>,
<option>tty</option>,
<option>syslog</option>,
- <option>kmsg</option> or
+ <option>kmsg</option>,
+ <option>journal</option>,
+ <option>syslog+console</option>,
+ <option>kmsg+console</option>,
+ <option>journal+console</option> or
<option>socket</option>. If set to
- <option>inherit</option> the file
+ <option>inherit</option>, the file
descriptor of standard input is
duplicated for standard output. If set
- to <option>null</option> standard
+ to <option>null</option>, standard
output will be connected to
<filename>/dev/null</filename>,
i.e. everything written to it will be
- lost. If set to <option>tty</option>
+ lost. If set to <option>tty</option>,
standard output will be connected to a
tty (as configured via
<varname>TTYPath=</varname>, see
below). If the TTY is used for output
- only the executed process will not
+ only, the executed process will not
become the controlling process of the
terminal, and will not fail or wait
for other processes to release the
terminal. <option>syslog</option>
connects standard output to the
<citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- system logger. <option>kmsg</option>
+ system syslog
+ service. <option>kmsg</option>
connects it with the kernel log buffer
which is accessible via
- <citerefentry><refentrytitle>dmesg</refentrytitle><manvolnum>1</manvolnum></citerefentry>. <option>socket</option>
- connects standard output to a socket
- from socket activation, semantics are
+ <citerefentry><refentrytitle>dmesg</refentrytitle><manvolnum>1</manvolnum></citerefentry>. <option>journal</option>
+ connects it with the journal which is
+ accessible via
+ <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ (Note that everything that is written
+ to syslog or kmsg is implicitly stored
+ in the journal as well, those options
+ are hence supersets of this
+ one). <option>syslog+console</option>,
+ <option>journal+console</option> and
+ <option>kmsg+console</option> work
+ similarly but copy the output to the
+ system console as
+ well. <option>socket</option> connects
+ standard output to a socket from
+ socket activation, semantics are
similar to the respective option of
<varname>StandardInput=</varname>.
- This setting defaults to
- <option>inherit</option>.</para></listitem>
+ This setting defaults to the value set
+ with
+ <option>DefaultStandardOutput=</option>
+ in
+ <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ which defaults to
+ <option>journal</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>StandardError=</varname></term>
available options are identical to
those of
<varname>StandardOutput=</varname>,
- whith one exception: if set to
+ with one exception: if set to
<option>inherit</option> the file
descriptor used for standard output is
duplicated for standard error. This
- setting defaults to
+ setting defaults to the value set with
+ <option>DefaultStandardError=</option>
+ in
+ <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ which defaults to
<option>inherit</option>.</para></listitem>
</varlistentry>
<varlistentry>
<filename>/dev/console</filename>.</para></listitem>
</varlistentry>
<varlistentry>
- <term><varname>SyslogIdentifer=</varname></term>
+ <term><varname>TTYReset=</varname></term>
+ <listitem><para>Reset the terminal
+ device specified with
+ <varname>TTYPath=</varname> before and
+ after execution. Defaults to
+ <literal>no</literal>.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><varname>TTYVHangup=</varname></term>
+ <listitem><para>Disconnect all clients
+ which have opened the terminal device
+ specified with
+ <varname>TTYPath=</varname>
+ before and after execution. Defaults
+ to
+ <literal>no</literal>.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><varname>TTYVTDisallocate=</varname></term>
+ <listitem><para>If the terminal
+ device specified with
+ <varname>TTYPath=</varname> is a
+ virtual console terminal, try to
+ deallocate the TTY before and after
+ execution. This ensures that the
+ screen and scrollback buffer is
+ cleared. Defaults to
+ <literal>no</literal>.</para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><varname>SyslogIdentifier=</varname></term>
<listitem><para>Sets the process name
to prefix log lines sent to syslog or
- the kernel log buffer with. If not set
+ the kernel log buffer with. If not set,
defaults to the process name of the
executed process. This option is only
useful when
prefixes may be disabled with
<varname>SyslogLevelPrefix=</varname>,
see below. For details see
- <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+ <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
Defaults to
<option>info</option>.</para></listitem>
argument. If true and
<varname>StandardOutput=</varname> or
<varname>StandardError=</varname> are
- set to <option>syslog</option> or
- <option>kmsg</option> log lines
+ set to <option>syslog</option>,
+ <option>kmsg</option> or
+ <option>journal</option>, log lines
written by the executed process that
are prefixed with a log level will be
passed on to syslog with this log
these prefixes is disabled and the
logged lines are passed on as-is. For
details about this prefixing see
- <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+ <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
Defaults to true.</para></listitem>
</varlistentry>
<term><varname>TimerSlackNSec=</varname></term>
<listitem><para>Sets the timer slack
in nanoseconds for the executed
- processes The timer slack controls the
- accuracy of wake-ups triggered by
+ processes. The timer slack controls
+ the accuracy of wake-ups triggered by
timers. See
<citerefentry><refentrytitle>prctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
for more information. Note that in
contrast to most other time span
- definitions this value is takes a
- nano-seconds integer and does not
- understand any other
- units.</para></listitem>
+ definitions this parameter takes an
+ integer value in nano-seconds if no
+ unit is specified. The usual time
+ units are understood
+ too.</para></listitem>
</varlistentry>
<varlistentry>
various resource limits for executed
processes. See
<citerefentry><refentrytitle>setrlimit</refentrytitle><manvolnum>2</manvolnum></citerefentry>
- for details.</para></listitem>
+ for details. Use the string
+ <varname>infinity</varname> to
+ configure no limit on a specific
+ resource.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>PAMName=</varname></term>
<listitem><para>Sets the PAM service
- name to set up a session as. If set
+ name to set up a session as. If set,
the executed process will be
registered as a PAM session under the
specified service name. This is only
useful in conjunction with the
<varname>User=</varname> setting. If
- not set no PAM session will be opened
+ not set, no PAM session will be opened
for the executed processes. See
<citerefentry><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for details.</para></listitem>
<varlistentry>
<term><varname>TCPWrapName=</varname></term>
<listitem><para>If this is a
- socket-activated service this sets the
+ socket-activated service, this sets the
tcpwrap service name to check the
permission for the current connection
with. This is only useful in
conjunction with socket-activated
services, and stream sockets (TCP) in
particular. It has no effect on other
- socket types (e.g. datagram/UDP) and on processes
- unrelated to socket-based
+ socket types (e.g. datagram/UDP) and
+ on processes unrelated to socket-based
activation. If the tcpwrap
- verification fails daemon start-up
+ verification fails, daemon start-up
will fail and the connection is
terminated. See
<citerefentry><refentrytitle>tcpd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
- for details.</para></listitem>
+ for details. Note that this option may
+ be used to do access control checks
+ only. Shell commands and commands
+ described in
+ <citerefentry><refentrytitle>hosts_options</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ are not supported.</para></listitem>
</varlistentry>
<varlistentry>
- <term><varname>Capabilities=</varname></term>
- <listitem><para>Controls the
+ <term><varname>CapabilityBoundingSet=</varname></term>
+
+ <listitem><para>Controls which
+ capabilities to include in the
+ capability bounding set for the
+ executed process. See
<citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
- set for the executed process. Take a
- capability string as described in
- <citerefentry><refentrytitle>cap_from_text</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
- Note that this capability set is
- usually influenced by the capabilities
- attached to the executed
- file.</para></listitem>
+ for details. Takes a whitespace-separated
+ list of capability names as read by
+ <citerefentry><refentrytitle>cap_from_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ e.g. <constant>CAP_SYS_ADMIN</constant>,
+ <constant>CAP_DAC_OVERRIDE</constant>,
+ <constant>CAP_SYS_PTRACE</constant>.
+ Capabilities listed will be included
+ in the bounding set, all others are
+ removed. If the list of capabilities
+ is prefixed with <literal>~</literal>,
+ all but the listed capabilities will
+ be included, the effect of the
+ assignment inverted. Note that this
+ option also affects the respective
+ capabilities in the effective,
+ permitted and inheritable capability
+ sets, on top of what
+ <varname>Capabilities=</varname>
+ does. If this option is not used, the
+ capability bounding set is not
+ modified on process execution, hence
+ no limits on the capabilities of the
+ process are enforced. This option may
+ appear more than once in which case
+ the bounding sets are merged. If the
+ empty string is assigned to this
+ option, the bounding set is reset to
+ the empty capability set, and all
+ prior settings have no effect. If set
+ to <literal>~</literal> (without any
+ further argument), the bounding set is
+ reset to the full set of available
+ capabilities, also undoing any
+ previous settings.</para></listitem>
</varlistentry>
<varlistentry>
<option>keep-caps-locked</option>,
<option>no-setuid-fixup</option>,
<option>no-setuid-fixup-locked</option>,
- <option>no-setuid-noroot</option> and/or
- <option>no-setuid-noroot-locked</option>.
- </para></listitem>
+ <option>noroot</option> and/or
+ <option>noroot-locked</option>. This
+ option may appear more than once in
+ which case the secure bits are
+ ORed. If the empty string is assigned
+ to this option, the bits are reset to
+ 0.</para></listitem>
</varlistentry>
<varlistentry>
- <term><varname>CapabilityBoundingSetDrop=</varname></term>
-
+ <term><varname>Capabilities=</varname></term>
<listitem><para>Controls the
- capability bounding set drop set for
- the executed process. See
<citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
- for details. Takes a list of
- capability names as read by
- <citerefentry><refentrytitle>cap_from_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
- </para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>ControlGroup=</varname></term>
-
- <listitem><para>Controls the control
- groups the executed processes shall be
- made members of. Takes a
- space-seperated list of cgroup
- identifiers. A cgroup identifier has a
- format like
- <filename>cpu:/foo/bar</filename>,
- where "cpu" identifies the kernel
- control group controller used, and
- <filename>/foo/bar</filename> is the
- control group path. The controller name
- and ":" may be omitted in which case
- the named systemd control group
- hierarchy is implied. Alternatively,
- the path and ":" may be omitted, in
- which case the default control group
- path for this unit is implied. This
- option may be used to place executed
- processes in arbitrary groups in
- arbitrary hierachies -- which can be
- configured externally with additional execution limits. By default
- systemd will place all executed
- processes in seperate per-unit control
- groups (named after the unit) in the
- systemd named hierarchy. Since every
- process can be in one group per
- hierarchy only overriding the control group
- path in the named systemd hierarchy
- will disable automatic placement in
- the default group. For details about control
- groups see <ulink
- url="http://www.kernel.org/doc/Documentation/cgroups/cgroups.txt">cgroups.txt</ulink>.</para></listitem>
+ set for the executed process. Take a
+ capability string describing the
+ effective, permitted and inherited
+ capability sets as documented in
+ <citerefentry><refentrytitle>cap_from_text</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+ Note that these capability sets are
+ usually influenced by the capabilities
+ attached to the executed file. Due to
+ that
+ <varname>CapabilityBoundingSet=</varname>
+ is probably the much more useful
+ setting.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>InaccessibleDirectories=</varname></term>
<listitem><para>Sets up a new
- file-system name space for executed
+ file system namespace for executed
processes. These options may be used
to limit access a process might have
- to the main file-system
+ to the main file system
hierarchy. Each setting takes a
- space-seperated list of absolute
+ space-separated list of absolute
directory paths. Directories listed in
<varname>ReadWriteDirectories=</varname>
are accessible from within the
usual file access controls would
permit this. Directories listed in
<varname>InaccessibleDirectories=</varname>
- will be made inaccesible for processes
- inside the namespace. Note that
- restricting access with these options
- does not extend to submounts of a
- directory. You must list submounts
- seperately in these setttings to
- ensure the same limited access. These
- options may be specified more than
- once in which case all directories
- listed will have limited access from
- within the
- namespace.</para></listitem>
+ will be made inaccessible for
+ processes inside the namespace. Note
+ that restricting access with these
+ options does not extend to submounts
+ of a directory. You must list
+ submounts separately in these settings
+ to ensure the same limited
+ access. These options may be specified
+ more than once in which case all
+ directories listed will have limited
+ access from within the namespace. If
+ the empty string is assigned to this
+ option, the specific list is reset, and
+ all prior assignments have no
+ effect.</para>
+ <para>Paths in
+ <varname>ReadOnlyDirectories=</varname>
+ and
+ <varname>InaccessibleDirectories=</varname>
+ may be prefixed with
+ <literal>-</literal>, in which case
+ they will be ignored when they do not
+ exist.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>PrivateTmp=</varname></term>
<listitem><para>Takes a boolean
- argument. If true sets up a new
- namespace for the executed processes
- and mounts a private
- <filename>/tmp</filename> directory
- inside it, that is not shared by
- processes outside of the
+ argument. If true, sets up a new file
+ system namespace for the executed
+ processes and mounts private
+ <filename>/tmp</filename> and
+ <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
processes via
- <filename>/tmp</filename>
- impossible. Defaults to false.</para></listitem>
+ <filename>/tmp</filename> or
+ <filename>/var/tmp</filename>
+ impossible. All temporary data created
+ 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>
+ <term><varname>PrivateNetwork=</varname></term>
+
+ <listitem><para>Takes a boolean
+ argument. If true, sets up a new
+ network namespace for the executed
+ processes and configures only the
+ loopback network device
+ <literal>lo</literal> inside it. No
+ other network devices will be
+ 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>
<varlistentry>
<option>shared</option>,
<option>slave</option> or
<option>private</option>, which
- control whether namespaces set up with
- <varname>ReadWriteDirectories=</varname>,
- <varname>ReadOnlyDirectories=</varname>
+ control whether the file system
+ namespace set up for this unit's
+ processes will receive or propagate
+ new mounts. See
+ <citerefentry><refentrytitle>mount</refentrytitle><manvolnum>2</manvolnum></citerefentry>
+ for details. Default to
+ <option>shared</option>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>UtmpIdentifier=</varname></term>
+
+ <listitem><para>Takes a four
+ character identifier string for an
+ utmp/wtmp entry for this service. This
+ should only be set for services such
+ as <command>getty</command>
+ implementations where utmp/wtmp
+ entries must be created and cleared
+ before and after execution. If the
+ configured string is longer than four
+ characters, it is truncated and the
+ terminal four characters are
+ used. This setting interprets %I style
+ string replacements. This setting is
+ unset by default, i.e. no utmp/wtmp
+ entries are created or cleaned up for
+ 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>
+
+ <listitem><para>Takes a boolean
+ argument. If true, causes <constant>SIGPIPE</constant> to be
+ ignored in the executed
+ process. Defaults to true because
+ <constant>SIGPIPE</constant> generally is useful only in
+ shell pipelines.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>NoNewPrivileges=</varname></term>
+
+ <listitem><para>Takes a boolean
+ argument. If true, ensures that the
+ service process and all its children
+ can never gain new privileges. This
+ option is more powerful than the respective
+ secure bits flags (see above), as it
+ also prohibits UID changes of any
+ kind. This is the simplest, most
+ effective way to ensure that a process
+ and its children can never elevate
+ privileges again.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>SystemCallFilter=</varname></term>
+
+ <listitem><para>Takes a space-separated
+ list of system call
+ names. If this setting is used, all
+ system calls executed by the unit
+ processes except for the listed ones
+ will result in immediate process
+ termination with the
+ <constant>SIGSYS</constant> signal
+ (whitelisting). If the first character
+ of the list is <literal>~</literal>,
+ the effect is inverted: only the
+ listed system calls will result in
+ immediate process termination
+ (blacklisting). If this option is used,
+ <varname>NoNewPrivileges=yes</varname>
+ is implied. This feature makes use of
+ the Secure Computing Mode 2 interfaces
+ of the kernel ('seccomp filtering')
+ and is useful for enforcing a minimal
+ sandboxing environment. Note that the
+ <function>execve</function>,
+ <function>rt_sigreturn</function>,
+ <function>sigreturn</function>,
+ <function>exit_group</function>,
+ <function>exit</function> system calls
+ are implicitly whitelisted and do not
+ need to be listed explicitly. This
+ option may be specified more than once
+ in which case the filter masks are
+ merged. If the empty string is
+ assigned, the filter is reset, all
+ prior assignments will have no
+ effect.</para>
+
+ <para>If you specify both types of
+ this option (i.e. whitelisting and
+ blacklisting) the first encountered
+ will take precedence and will dictate
+ the default action (termination or
+ approval of a system call). Then the
+ next occurrences of this option will
+ add or delete the listed system calls
+ from the set of the filtered system
+ calls, depending of its type and the
+ default action (e.g. You have started
+ with a whitelisting of
+ <function>read</function> and
+ <function>write</function> and right
+ after it add a blacklisting of
+ <function>write</function>, then
+ <function>write</function> will be
+ removed from the set).
+ </para></listitem>
+
+ <para>Note that setting
+ <varname>SystemCallFilter=</varname>
+ implies a
+ <varname>SystemCallArchitectures=</varname>
+ setting of <literal>native</literal>
+ (see below), unless that option is
+ configured otherwise.</para>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>SystemCallErrorNumber=</varname></term>
+
+ <listitem><para>Takes an
+ <literal>errno</literal> error number
+ name to return when the system call
+ filter configured with
+ <varname>SystemCallFilter=</varname>
+ is triggered, instead of terminating
+ the process immediately. Takes an
+ error name such as
+ <literal>EPERM</literal>,
+ <literal>EACCES</literal> or
+ <literal>EUCLEAN</literal>. When this
+ setting is not used, or when the empty
+ string is assigned the process will be
+ terminated immediately when the filter
+ is triggered.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>SystemCallArchitectures=</varname></term>
+
+ <listitem><para>Takes a space
+ separated list of architecture
+ identifiers to include in the system
+ call filter. The known architecture
+ identifiers are
+ <literal>x86</literal>,
+ <literal>x86-64</literal>,
+ <literal>x32</literal>,
+ <literal>arm</literal> as well as the
+ special identifier
+ <literal>native</literal>. Only system
+ calls of the specified architectures
+ will be permitted to processes of this
+ unit. This is an effective way to
+ disable compatibility with non-native
+ architectures for processes, for
+ example to prohibit execution of 32bit
+ x86 binaries on 64bit x86-64
+ systems. The special
+ <literal>native</literal> identifier
+ implicitly maps to the native
+ architecture of the system (or more
+ strictly: to the architecture the
+ system manager is compiled for). Note
+ that setting this option to a
+ non-empty list implies that
+ <literal>native</literal> is included
+ too. By default this option is set to
+ the empty list, i.e. no architecture
+ system call filtering is applied. Note
+ that configuring a system call filter
+ with
+ <varname>SystemCallFilter=</varname>
+ (above) implies a
+ <literal>native</literal> architecture
+ list, unless configured
+ otherwise.</para></listitem>
+ </varlistentry>
+
+ </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
- <varname>InaccessibleDirectories=</varname>
- receive or propagate new mounts
- from/to the main namespace. See
- <citerefentry><refentrytitle>mount</refentrytitle><manvolnum>1</manvolnum></citerefentry>
- for details. Defaults to
- <option>shared</option>, i.e. the new
- namespace will both receive new mount
- points from the main namespace as well
- as propagate new mounts to
- it.</para></listitem>
+ <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>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ <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.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