systemd.execsystemdDeveloperLennartPoetteringlennart@poettering.netsystemd.exec5systemd.execsystemd execution environment configurationsystemd.service,
systemd.socket,
systemd.mount,
systemd.swapDescriptionUnit 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.unit5
for the common options of all unit configuration
files, and
systemd.service5,
systemd.socket5,
systemd.swap5
and
systemd.mount5
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.OptionsWorkingDirectory=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
chroot2
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
setpriority2
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
for details.IOSchedulingClass=Sets the IO scheduling
class for executed processes. Takes an
integer between 0 and 3 or one of the
strings ,
,
or
. See
ioprio_set2
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_set2
for details.CPUSchedulingPolicy=Sets the CPU
scheduling policy for executed
processes. Takes one of
,
,
,
or
. See
sched_setscheduler2
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_setscheduler2
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_setscheduler2
for details. Defaults to false.CPUAffinity=Controls the CPU
affinity of the executed
processes. Takes a space-separated
list of CPU indexes. See
sched_setaffinity2
for details.UMask=Controls the file mode
creation mask. Takes an access mode in
octal notation. See
umask2
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
environ7
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 ,
,
,
or
. If
is selected
standard input will be connected to
/dev/null,
i.e. all read attempts by the process
will result in immediate EOF. If
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.
is similar to ,
but the executed process is forcefully
and immediately made the controlling
process of the terminal, potentially
removing previous controlling
processes from the
terminal. is
similar to but if
the terminal already has a controlling
process start-up of the executed
process fails. The
option is only
valid in socket-activated services,
and only when the socket configuration
file (see
systemd.socket5
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
inetd8
daemon. This setting defaults to
.StandardOutput=Controls where file
descriptor 1 (STDOUT) of the executed
processes is connected to. Takes one
of ,
,
,
,
,
,
,
,
or
. If set to
the file
descriptor of standard input is
duplicated for standard output. If set
to standard
output will be connected to
/dev/null,
i.e. everything written to it will be
lost. If set to
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.
connects standard output to the
syslog3
system syslog
service.
connects it with the kernel log buffer
which is accessible via
dmesg1.
connects it with the journal which is
accessible via
journalctl1
(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). ,
and
work
similarly but copy the output to the
system console as
well. 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
in
systemd.conf5,
which defaults to
.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
the file
descriptor used for standard output is
duplicated for standard error. This
setting defaults to the value set with
in
systemd.conf5,
which defaults to
.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 or
.SyslogFacility=Sets the syslog
facility to use when logging to
syslog. One of ,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
or
. See
syslog3
for details. This option is only
useful when
StandardOutput= or
StandardError= are
set to .
Defaults to
.SyslogLevel=Default syslog level
to use when logging to syslog or the
kernel log buffer. One of
,
,
,
,
,
,
,
. See
syslog3
for details. This option is only
useful when
StandardOutput= or
StandardError= are
set to or
. 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-daemon7.
Defaults to
.SyslogLevelPrefix=Takes a boolean
argument. If true and
StandardOutput= or
StandardError= are
set to or
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-daemon7.
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
prctl2
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
setrlimit2
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
pam8
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
tcpd8
for details. Note that this option may
be used to do access control checks
only. Shell commands and commands
described in
hosts_options5
are not supported.CapabilityBoundingSet=Controls which
capabilities to include in the
capability bounding set for the
executed process. See
capabilities7
for details. Takes a whitespace
separated list of capability names as
read by
cap_from_name3.
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
capabilities7
for details. Takes a list of strings:
,
,
,
,
and/or
.
Capabilities=Controls the
capabilities7
set for the executed process. Take a
capability string describing the
effective, permitted and inherited
capability sets as documented in
cap_from_text3.
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.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.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. 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.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.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.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.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.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:
,
or
, which
control whether namespaces set up with
ReadWriteDirectories=,
ReadOnlyDirectories=
and
InaccessibleDirectories=
receive or propagate new mounts
from/to the main namespace. See
mount1
for details. Defaults to
, 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 Alsosystemd1,
systemctl8,
journalctl8,
systemd.unit5,
systemd.service5,
systemd.socket5,
systemd.swap5,
systemd.mount5