SYSTEMD.EXEC(5)systemd.execSYSTEMD.EXEC(5)NAMEsystemd.exec - systemd execution environment configuration
SYNOPSIS
systemd.service, systemd.socket, systemd.mount, systemd.swap
DESCRIPTION
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.
This man page lists the configuration options shared by these four unit
types. See systemd.unit(5) for the common options of all unit
configuration files, and systemd.service(5), systemd.socket(5),
systemd.swap(5) and systemd.mount(5) 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 type.
OPTIONS
WorkingDirectory=
Takes an absolute directory path. Sets the working directory for
executed processes.
RootDirectory=
Takes an absolute directory path. Sets the root directory for
executed processes, with the chroot(2) system call. If this is used
it must be ensured that the process and all its auxiliary files are
available in the chroot() jail.
User=, Group=
Sets the Unix user resp. group the processes are executed as. Takes
a single user resp. group name or ID as argument. If no group is
set the default group of the user is chosen.
SupplementaryGroups=
Sets the supplementary Unix groups the processes are executed 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 extends the list of supplementary groups configured in
the system group database for the user.
Nice=
Sets the default nice level (scheduling priority) for executed
processes. Takes an integer between -20 (highest priority) and 19
(lowest priority). See setpriority(2) for details.
OOMScoreAdjust=
Sets the adjustment level for the Out-Of-Memory killer for executed
processes. Takes an integer between -1000 (to disable OOM killing
for this process) and 1000 (to make killing of this process under
memory pressure very likely). See proc.txt[1] for details.
IOSchedulingClass=
Sets the IO scheduling class for executed processes. Takes an
integer between 0 and 3 or one of the strings none, realtime,
best-effort or idle. See ioprio_set(2) for details.
IOSchedulingPriority=
Sets the IO scheduling priority for executed processes. Takes an
integer between 0 (highest priority) and 7 (lowest priority). The
available priorities depend on the selected IO scheduling class
(see above). See ioprio_set(2) for details.
CPUSchedulingPolicy=
Sets the CPU scheduling policy for executed processes. Takes one of
other, batch, idle, fifo or rr. See sched_setscheduler(2) for
details.
CPUSchedulingPriority=
Sets the CPU scheduling priority for executed processes. Takes an
integer between 1 (lowest priority) and 99 (highest priority). The
available priority range depends on the selected CPU scheduling
policy (see above). See sched_setscheduler(2) for details.
CPUSchedulingResetOnFork=
Takes a boolean argument. If true elevated CPU scheduling
priorities and policies will be reset when the executed processes
fork, and can hence not leak into child processes. See
sched_setscheduler(2) for details. Defaults to false.
CPUAffinity=
Controls the CPU affinity of the executed processes. Takes a
space-separated list of CPU indexes. See sched_setaffinity(2) for
details.
UMask=
Controls the file mode creation mask. Takes an access mode in octal
notation. See umask(2) for details. Defaults to 0022.
Environment=
Sets environment variables for executed 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 environ(7) for details.
EnvironmentFile=
Similar to Environment= but reads the environment variables from a
text file. The text file should 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 of assignments,
unless you use double quotes ("). The argument passed should be an
absolute file name, 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 directive
will be read shortly before the process is executed. Settings from
these files override settings made with Environment=. 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.
StandardInput=
Controls where file descriptor 0 (STDIN) of the executed processes
is connected to. Takes one of null, tty, tty-force, tty-fail or
socket. If null is selected standard input will be connected to
/dev/null, i.e. all read attempts by the process will result in
immediate EOF. If tty is selected standard input is connected to a
TTY (as configured by TTYPath=, see below) and the executed process
becomes the controlling process of the terminal. If the terminal is
already being controlled by another process the executed process
waits until the current controlling process releases the terminal.
tty-force is similar to tty, but the executed process is forcefully
and immediately made the controlling process of the terminal,
potentially removing previous controlling processes from the
terminal. tty-fail is similar to tty but if the terminal already
has a controlling process start-up of the executed process fails.
The socket option is only valid in socket-activated services, and
only when the socket configuration file (see systemd.socket(5) for
details) specifies a single socket 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 with
daemons designed for use with the traditional inetd(8) daemon. This
setting defaults to null.
StandardOutput=
Controls where file descriptor 1 (STDOUT) of the executed processes
is connected to. Takes one of inherit, null, tty, syslog, kmsg,
journal, syslog+console, kmsg+console, journal+console or socket.
If set to inherit the file descriptor of standard input is
duplicated for standard output. If set to null standard output will
be connected to /dev/null, i.e. everything written to it will be
lost. If set to tty standard output will be connected to a tty (as
configured via TTYPath=, see below). If the TTY is used for output
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. syslog connects standard output to the
syslog(3) system syslog service. kmsg connects it with the kernel
log buffer which is accessible via dmesg(1). journal connects it
with the journal which is accessible via journalctl(1) (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). syslog+console, journal+console and kmsg+console work
similarly but copy the output to the system console as well.
socket connects standard output to a socket from socket activation,
semantics are similar to the respective option of StandardInput=.
This setting defaults to the value set with DefaultStandardOutput=
in systemd.conf(5), which defaults to journal.
StandardError=
Controls where file descriptor 2 (STDERR) of the executed processes
is connected to. The available options are identical to those of
StandardOutput=, with one exception: if set to inherit the file
descriptor used for standard output is duplicated for standard
error. This setting defaults to the value set with
DefaultStandardError= in systemd.conf(5), which defaults to
inherit.
TTYPath=
Sets the terminal device node to use if standard input, output or
stderr are connected to a TTY (see above). Defaults to
/dev/console.
TTYReset=
Reset the terminal device specified with TTYPath= before and after
execution. Defaults to no.
TTYVHangup=
Disconnect all clients which have opened the terminal device
specified with TTYPath= before and after execution. Defaults to no.
TTYVTDisallocate=
If the the terminal device specified with TTYPath= 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 no.
SyslogIdentifier=
Sets the process name to prefix log lines sent to syslog or the
kernel log buffer with. If not set defaults to the process name of
the executed process. This option is only useful when
StandardOutput= or StandardError= are set to syslog or kmsg.
SyslogFacility=
Sets the syslog facility to use when logging to syslog. One of
kern, user, mail, daemon, auth, syslog, lpr, news, uucp, cron,
authpriv, ftp, local0, local1, local2, local3, local4, local5,
local6 or local7. See syslog(3) for details. This option is only
useful when StandardOutput= or StandardError= are set to syslog.
Defaults to daemon.
SyslogLevel=
Default syslog level to use when logging to syslog or the kernel
log buffer. One of emerg, alert, crit, err, warning, notice, info,
debug. See syslog(3) for details. This option is only useful when
StandardOutput= or StandardError= are set to syslog or kmsg. Note
that individual lines output by the daemon might be prefixed with a
different log level which can be used to override the default log
level specified here. The interpretation of these prefixes may be
disabled with SyslogLevelPrefix=, see below. For details see sd-
daemon(7). Defaults to info.
SyslogLevelPrefix=
Takes a boolean argument. If true and StandardOutput= or
StandardError= are set to syslog or kmsg log lines written by the
executed process that are prefixed with a log level will be passed
on to syslog with this log level set but the prefix removed. If set
to false, the interpretation of these prefixes is disabled and the
logged lines are passed on as-is. For details about this prefixing
see sd-daemon(7). Defaults to true.
TimerSlackNSec=
Sets the timer slack in nanoseconds for the executed processes. The
timer slack controls the accuracy of wake-ups triggered by timers.
See prctl(2) for more information. Note that in contrast to most
other time span definitions this parameter takes an integer value
in nano-seconds if no unit is specified. The usual time units are
understood too.
LimitCPU=, LimitFSIZE=, LimitDATA=, LimitSTACK=, LimitCORE=, LimitRSS=,
LimitNOFILE=, LimitAS=, LimitNPROC=, LimitMEMLOCK=, LimitLOCKS=,
LimitSIGPENDING=, LimitMSGQUEUE=, LimitNICE=, LimitRTPRIO=,
LimitRTTIME=
These settings control various resource limits for executed
processes. See setrlimit(2) for details. Use the string infinity to
configure no limit on a specific resource.
PAMName=
Sets the PAM service 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
User= setting. If not set no PAM session will be opened for the
executed processes. See pam(8) for details.
TCPWrapName=
If this is a 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 activation. If the tcpwrap verification fails daemon
start-up will fail and the connection is terminated. See tcpd(8)
for details. Note that this option may be used to do access control
checks only. Shell commands and commands described in
hosts_options(5) are not supported.
CapabilityBoundingSet=
Controls which capabilities to include in the capability bounding
set for the executed process. See capabilities(7) for details.
Takes a whitespace separated list of capability names as read by
cap_from_name(3). Capabilities listed will be included in the
bounding set, all others are removed. If the list of capabilities
is prefixed with ~ all but the listed capabilities will be
included, the effect of the assignment inverted. Note that this
option also effects the respective capabilities in the effective,
permitted and inheritable capability sets, on top of what
Capabilities= 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.
SecureBits=
Controls the secure bits set for the executed process. See
capabilities(7) for details. Takes a list of strings: keep-caps,
keep-caps-locked, no-setuid-fixup, no-setuid-fixup-locked, noroot
and/or noroot-locked.
Capabilities=
Controls the capabilities(7) set for the executed process. Take a
capability string describing the effective, permitted and inherited
capability sets as documented in cap_from_text(3). Note that these
capability sets are usually influenced by the capabilities attached
to the executed file. Due to that CapabilityBoundingSet= is
probably the much more useful setting.
ControlGroup=
Controls the control groups the executed processes shall be made
members of. Takes a space-separated list of cgroup identifiers. A
cgroup identifier has a format like cpu:/foo/bar, where "cpu"
identifies the kernel control group controller used, and /foo/bar
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 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 recommended to manipulate
the service control group path in the systemd named hierarchy. For
details about control groups see cgroups.txt[2].
ControlGroupModify=
Takes a boolean argument. If true, the control groups created for
this unit will be owned by the user specified with User= (and the
appropriate group), and he/she can create subgroups as well as add
processes to the group.
ControlGroupPersistent=
Takes a boolean argument. If true, the control groups created for
this unit will be marked to be persistent, i.e. systemd will not
remove them when stopping the unit. The default is false, meaning
that the control groups will be removed when the unit is stopped.
For details about the semantics of this logic see
PaxControlGroups[3].
ControlGroupAttribute=
Set a specific control group attribute for executed processes, and
(if needed) add the the executed processes to a cgroup in the
hierarchy of the controller the attribute belongs to. Takes two
space-separated arguments: the attribute name (syntax is cpu.shares
where cpu refers to a specific controller and shares to the
attribute name), and the attribute value. Example:
ControlGroupAttribute=cpu.shares 512. If this option is used for an
attribute that belongs to a kernel controller hierarchy the unit is
not already configured to be added to (for example via the
ControlGroup= option) then the unit will be added to the controller
and the default unit cgroup path is implied. Thus, using
ControlGroupAttribute= is in most case sufficient to make use of
control group enforcements, explicit ControlGroup= are only
necessary in case the implied default control group path for a
service is not desirable. For details about control group
attributes see cgroups.txt[2]. This option may appear more than
once, in order to set multiple control group attributes.
CPUShares=
Assign the specified overall CPU time shares to the processes
executed. Takes an integer value. This controls the cpu.shares
control group attribute, which defaults to 1024. For details about
this control group attribute see sched-design-CFS.txt[4].
MemoryLimit=, MemorySoftLimit=
Limit the overall memory usage of the executed processes to a
certain size. Takes a memory size in bytes. If 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 memory.limit_in_bytes and
memory.soft_limit_in_bytes control group attributes. For details
about these control group attributes see memory.txt[5].
DeviceAllow=, DeviceDeny=
Control access to specific device nodes by the executed processes.
Takes two space separated strings: a device node path (such as
/dev/null) followed by a combination of r, w, m to control reading,
writing resp. creating of the specific device node by the unit.
This controls the devices.allow and devices.deny control group
attributes. For details about these control group attributes see
devices.txt[6].
BlockIOWeight=
Set the default or per-device overall block IO weight value for the
executed processes. Takes either a single weight value (between 10
and 1000) to set the default block IO weight, or a space separated
pair of a file path and a weight value to specify the device
specific weight value (Example: "/dev/sda 500"). The file path may
be specified as path to a block device node or as any other file in
which case the backing block device of the file system of the file
is determined. This controls the blkio.weight and
blkio.weight_device control group attributes, which default to
1000. Use this option multiple times to set weights for multiple
devices. For details about these control group attributes see
blkio-controller.txt[7].
BlockIOReadBandwidth=, BlockIOWriteBandwidth=
Set the per-device overall block IO bandwith limit for the executed
processes. Takes a space separated pair of a file path and a
bandwith value (in bytes per second) to specify the device specific
bandwidth. The file path may be specified as path to a block device
node or as any other file in which case the backing block device of
the file system of the file is determined. If the bandwith is
suffixed with K, M, G, or T the specified bandwith is parsed as
Kilobytes, Megabytes, Gigabytes, resp. Terabytes (Example:
"/dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 5M"). This
controls the blkio.read_bps_device and blkio.write_bps_device
control group attributes. Use this option multiple times to set
bandwith limits for multiple devices. For details about these
control group attributes see blkio-controller.txt[7].
ReadWriteDirectories=, ReadOnlyDirectories=, InaccessibleDirectories=
Sets up a new file-system name space for executed processes. These
options may be used to limit access a process might have to the
main file-system hierarchy. Each setting takes a space-separated
list of absolute directory paths. Directories listed in
ReadWriteDirectories= are accessible from within the namespace with
the same access rights as from outside. Directories listed in
ReadOnlyDirectories= are accessible for reading only, writing will
be refused even if the usual file access controls would permit
this. Directories listed in InaccessibleDirectories= 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.
PrivateTmp=
Takes a boolean argument. If true sets up a new file system
namespace for the executed processes and mounts a private /tmp
directory 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 /tmp
impossible. Defaults to false.
PrivateNetwork=
Takes a boolean argument. If true sets up a new network namespace
for the executed processes and configures only the loopback network
device lo 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.
MountFlags=
Takes a mount propagation flag: shared, slave or private, which
control whether the file system namespace set up for this unit's
processes will receive or propagate new mounts. See mount(1) for
details. Default to shared.
UtmpIdentifier=
Takes a a four character identifier string for an utmp/wtmp entry
for this service. This should only be set for services such as
getty 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.
IgnoreSIGPIPE=
Takes a boolean argument. If true causes SIGPIPE to be ignored in
the executed process. Defaults to true, since SIGPIPE generally is
useful only in shell pipelines.
SEE ALSOsystemd(1), systemctl(8), journalctl(8), systemd.unit(5),
systemd.service(5), systemd.socket(5), systemd.swap(5),
systemd.mount(5)AUTHOR
Lennart Poettering <lennart@poettering.net>
Developer
NOTES
1. proc.txt
http://www.kernel.org/doc/Documentation/filesystems/proc.txt
2. cgroups.txt
http://www.kernel.org/doc/Documentation/cgroups/cgroups.txt
3. PaxControlGroups
http://www.freedesktop.org/wiki/Software/systemd/PaxControlGroups
4. sched-design-CFS.txt
http://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt
5. memory.txt
http://www.kernel.org/doc/Documentation/cgroups/memory.txt
6. devices.txt
http://www.kernel.org/doc/Documentation/cgroups/devices.txt
7. blkio-controller.txt
http://www.kernel.org/doc/Documentation/cgroups/blkio-controller.txt
systemd 02/15/2013 SYSTEMD.EXEC(5)
