<refnamediv>
<refname>systemd.exec</refname>
- <refpurpose>systemd execution environment configuration</refpurpose>
+ <refpurpose>Execution environment configuration</refpurpose>
</refnamediv>
<refsynopsisdiv>
for more information on the specific unit
configuration files. The execution specific
configuration options are configured in the [Service],
- [Socket], [Mount] resp. [Swap] section, depending on the unit
+ [Socket], [Mount], or [Swap] sections, depending on the unit
type.</para>
</refsect1>
<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>
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 extends 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>
<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>
<listitem><para>Controls the CPU
affinity of the executed
processes. Takes a space-separated
- list of CPU indexes. See
+ 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>
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
+ 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, and $ 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>.
+ </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>
contain new-line separated variable
assignments. Empty lines and lines
starting with ; or # will be ignored,
- which may be used for commenting. The
- parser strips leading and
- trailing whitespace from the values
+ 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 (").
- The
- argument passed should be an absolute
- file name, optionally prefixed with
+ double quotes (").</para>
+
+ <para>The argument passed should be an
+ absolute file name or wildcard
+ expression, optionally prefixed with
"-", which indicates that if the file
does not exist it won't be read and no
- error or warning message is
- logged. The files listed with this
+ 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
these files the files will be read in
the order they are specified and the
later setting will override the
- earlier setting. </para></listitem>
+ earlier setting.</para></listitem>
</varlistentry>
<varlistentry>
</varlistentry>
<varlistentry>
<term><varname>TTYVTDisallocate=</varname></term>
- <listitem><para>If the the terminal
+ <listitem><para>If the terminal
device specified with
<varname>TTYPath=</varname> is a
virtual console terminal try to
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
capability bounding set is not
modified on process execution, hence
no limits on the capabilities of the
- process are
- enforced.</para></listitem>
+ 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, and all prior
+ settings have no
+ effect.</para></listitem>
</varlistentry>
<varlistentry>
<option>no-setuid-fixup</option>,
<option>no-setuid-fixup-locked</option>,
<option>noroot</option> and/or
- <option>noroot-locked</option>.
- </para></listitem>
+ <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>
groups the executed processes shall be
made members of. Takes a
space-separated list of cgroup
- identifiers. A cgroup identifier has a
- format like
+ identifiers. A cgroup identifier is
+ formatted like
<filename>cpu:/foo/bar</filename>,
- where "cpu" identifies the kernel
+ where "cpu" indicates the kernel
control group controller used, and
<filename>/foo/bar</filename> is the
control group path. The controller
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 hierarchies -- which can be
- configured externally with additional
- execution limits. By default systemd
- will place all executed processes in
- separate 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. This option is
- primarily intended to place executed
- processes in specific paths in
- specific kernel controller
- hierarchies. It is however not
+ path for this unit is implied.</para>
+
+ <para>This option may be used to place
+ executed processes in arbitrary groups
+ in arbitrary hierarchies -- which may
+ then be externally configured with
+ additional execution limits. By
+ default systemd will place all
+ executed processes in separate
+ per-unit control groups (named after
+ the unit) in the systemd named
+ hierarchy. This option is primarily
+ intended to place executed processes
+ in specific paths in specific kernel
+ controller hierarchies. It is not
recommended to manipulate the service
control group path in the systemd
named hierarchy. For details about
control groups see <ulink
- url="http://www.kernel.org/doc/Documentation/cgroups/cgroups.txt">cgroups.txt</ulink>.</para></listitem>
+ url="http://www.kernel.org/doc/Documentation/cgroups/cgroups.txt">cgroups.txt</ulink>.</para>
+
+ <para>This option may appear more than
+ once, in which case the list of
+ control group assignments is
+ merged. If the same hierarchy gets two
+ different paths assigned only the
+ later setting will take effect. If the
+ empty string is assigned to this
+ option the list of control group
+ assignments is reset, all previous
+ assignments will have no
+ effect.</para>
+
+ <para>Note that the list of control
+ group assignments of a unit is
+ extended implicitly based on the
+ settings of
+ <varname>DefaultControllers=</varname>
+ of
+ <citerefentry><refentrytitle>systemd.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ but a unit's
+ <varname>ControlGroup=</varname>
+ setting for a specific controller
+ takes precedence.</para></listitem>
</varlistentry>
<varlistentry>
<listitem><para>Set a specific control
group attribute for executed
- processes, and (if needed) add the the
+ processes, and (if needed) add the
executed processes to a cgroup in the
hierarchy of the controller the
attribute belongs to. Takes two
the controller and the default unit
cgroup path is implied. Thus, using
<varname>ControlGroupAttribute=</varname>
- is in most case sufficient to make use
- of control group enforcements,
+ is in most cases sufficient to make
+ use of control group enforcements,
explicit
<varname>ControlGroup=</varname> are
only necessary in case the implied
url="http://www.kernel.org/doc/Documentation/cgroups/cgroups.txt">cgroups.txt</ulink>. This
option may appear more than once, in
order to set multiple control group
- attributes.</para></listitem>
+ attributes. If this option is used
+ multiple times for the same cgroup
+ attribute only the later setting takes
+ effect. If the empty string is
+ assigned to this option the list of
+ attributes is reset, all previous
+ cgroup attribute settings have no
+ effect, including those done with
+ <varname>CPUShares=</varname>,
+ <varname>MemoryLimit=</varname>,
+ <varname>MemorySoftLimit</varname>,
+ <varname>DeviceAllow=</varname>,
+ <varname>DeviceDeny=</varname>,
+ <varname>BlockIOWeight=</varname>,
+ <varname>BlockIOReadBandwidth=</varname>,
+ <varname>BlockIOWriteBandwidth=</varname>.
+ </para></listitem>
</varlistentry>
<varlistentry>
the value is suffixed with K, M, G or
T the specified memory size is parsed
as Kilobytes, Megabytes, Gigabytes,
- resp. Terabytes (to the base
- 1024). This controls the
+ or Terabytes (to the base
+ 1024), respectively. This controls the
<literal>memory.limit_in_bytes</literal>
and
<literal>memory.soft_limit_in_bytes</literal>
path (such as
<filename>/dev/null</filename>)
followed by a combination of r, w, m
- to control reading, writing resp.
+ to control reading, writing, or
creating of the specific device node
- by the unit. This controls the
+ by the unit, respectively. This controls the
<literal>devices.allow</literal>
and
<literal>devices.deny</literal>
If the bandwidth is suffixed with K, M,
G, or T the specified bandwidth is
parsed as Kilobytes, Megabytes,
- Gigabytes, resp. Terabytes (Example:
+ Gigabytes, or Terabytes, respectively (Example:
"/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0
5M"). This controls the
<literal>blkio.read_bps_device</literal>
usual file access controls would
permit this. Directories listed in
<varname>InaccessibleDirectories=</varname>
- 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.</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></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>
- 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>
+ 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 a four
+ <listitem><para>Takes a four
character identifier string for an
utmp/wtmp entry for this service. This
should only be set for services such
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
+ process except for the listed ones
+ will result in immediate process
+ termination with the SIGSYS 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 don't
+ 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></listitem>
+ </varlistentry>
+
</variablelist>
</refsect1>
<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>,
- <citerefentry><refentrytitle>systemd.mount</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.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
</para>
</refsect1>
~ianmdlvl / elogind.git / blobdiff