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SYSTEMD.EXEC(5) | systemd.exec | SYSTEMD.EXEC(5) |
NAME¶
systemd.exec - systemd execution environment configurationSYNOPSIS¶
systemd.service, systemd.socket, systemd.mount, systemd.swapDESCRIPTION¶
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 systemd-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 and does not understand any other units.
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 does not actually set or unset any
capabilities in the effective, permitted or inherited capability sets. That's
what Capabilities= is for. 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 namespaces set up with
ReadWriteDirectories=, ReadOnlyDirectories= and
InaccessibleDirectories= receive or propagate new mounts from/to the
main namespace. See mount(1) for details. Defaults to shared,
i.e. the new namespace will both receive new mount points from the main
namespace as well as propagate new mounts to it.
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 ALSO¶
AUTHOR¶
Lennart Poettering <lennart@poettering.net>Developer
NOTES¶
- 1.
- proc.txt
- 2.
- cgroups.txt
- 3.
- PaxControlGroups
- 4.
- sched-design-CFS.txt
- 5.
- memory.txt
- 6.
- devices.txt
- 7.
- blkio-controller.txt
10/07/2013 | systemd |