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SYSTEMD.EXEC(5) | systemd.exec | SYSTEMD.EXEC(5) |
NAME¶
systemd.exec - Execution environment configurationSYNOPSIS¶
service.service, socket.socket, mount.mount, swap.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], or [Swap] sections, depending on the unit type.AUTOMATIC DEPENDENCIES¶
A few execution parameters result in additional, automatic dependencies to be added. Units with WorkingDirectory= or RootDirectory= set automatically gain dependencies of type Requires= and After= on all mount units required to access the specified paths. This is equivalent to having them listed explicitly in RequiresMountsFor=. Similar, units with PrivateTmp= enabled automatically get mount unit dependencies for all mounts required to access /tmp and /var/tmp. Units whose standard output or error output is connected to journal, syslog or kmsg (or their combinations with console output, see below) automatically acquire dependencies of type After= on systemd-journald.socket.OPTIONS¶
WorkingDirectory=Takes an absolute directory path, or the special value
"~". Sets the working directory for executed processes. If set to
"~", the home directory of the user specified in User= is
used. 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. If
the setting is prefixed with the "-" character, a missing working
directory is not considered fatal. Note that setting this parameter might
result in additional dependencies to be added to the unit (see above).
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 binary and all its auxiliary files
are available in the chroot() jail. Note that setting this parameter
might result in additional dependencies to be added to the unit (see
above).
User=, Group=
Sets the Unix user 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 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. 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.
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 I/O 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 I/O scheduling priority for executed processes.
Takes an integer between 0 (highest priority) and 7 (lowest priority). The
available priorities depend on the selected I/O 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.
The available priority range depends on the selected CPU scheduling policy
(see above). For real-time scheduling policies an integer between 1 (lowest
priority) and 99 (highest priority) can be used. 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 list of CPU indices or ranges separated by either whitespace or
commas. CPU ranges are specified by the lower and upper CPU indices separated
by a dash. This option may be specified more than once, in which case the
specified 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
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. 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.
Example:
gives three variables "VAR1", "VAR2", "VAR3" with
the values "word1 word2", "word3", "$word 5 6".
See environ(7) for details about environment variables.
EnvironmentFile=
Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"
Similar to Environment= but reads the environment
variables from a text file. The text file should contain new-line-separated
variable assignments. Empty lines, lines without an "=" separator,
or lines starting with ; or # will be ignored, 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 filename or wildcard expression,
optionally prefixed with "-", 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.
The files listed with this directive will be read shortly before the process is
executed (more specifically, after all processes from a previous unit state
terminated. This means you can generate these files in one unit state, and
read it with this option in the next).
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.
PassEnvironment=
Pass environment variables from the systemd system
manager to executed processes. Takes a space-separated list of variable names.
This option may be specified more than once, in which case all listed
variables will be set. If the empty string is assigned to this option, the
list of environment variables is reset, all prior assignments have no effect.
Variables that are not set in the system manager will not be passed and will
be silently ignored.
Variables passed from this setting are overridden by those passed from
Environment= or EnvironmentFile=.
Example:
passes three variables "VAR1", "VAR2", "VAR3" with
the values set for those variables in PID1.
See environ(7) for details about environment variables.
StandardInput=
PassEnvironment=VAR1 VAR2 VAR3
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, journal, syslog, kmsg,
journal+console, syslog+console, kmsg+console or
socket.
inherit duplicates the file descriptor of standard input for standard
output.
null connects standard output to /dev/null, i.e. everything written to it
will be lost.
tty connects standard output 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.
journal connects standard output with the journal which is accessible via
journalctl(1). Note that everything that is written to syslog or kmsg
(see below) is implicitly stored in the journal as well, the specific two
options listed below are hence supersets of this one.
syslog connects standard output to the syslog(3) system syslog
service, in addition to the journal. Note that the journal daemon is usually
configured to forward everything it receives to syslog anyway, in which case
this option is no different from journal.
kmsg connects standard output with the kernel log buffer which is
accessible via dmesg(1), in addition to the journal. The journal daemon
might be configured to send all logs to kmsg anyway, in which case this option
is no different from journal.
journal+console, syslog+console and kmsg+console work in a
similar way as the three options above but copy the output to the system
console as well.
socket connects standard output to a socket acquired via socket
activation. The semantics are similar to the same option of
StandardInput=.
If the standard output (or error output, see below) of a unit is connected to
the journal, syslog or the kernel log buffer, the unit will implicitly gain a
dependency of type After= on systemd-journald.socket (also see the
automatic dependencies section above).
This setting defaults to the value set with DefaultStandardOutput= in
systemd-system.conf(5), which defaults to journal. Note that
setting this parameter might result in additional dependencies to be added to
the unit (see above).
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-system.conf(5), which defaults to inherit. Note that
setting this parameter might result in additional dependencies to be added to
the unit (see above).
TTYPath=
Sets the terminal device node to use if standard input,
output, or error 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 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 the
logging system 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,
journal or kmsg (or to the same settings in combination with
+console).
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=
The 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(3).
Defaults to info.
SyslogLevelPrefix=
Takes a boolean argument. If true and
StandardOutput= or StandardError= are set to syslog,
kmsg or journal, 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(3). 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=
Set soft and hard limits on various resources for
executed processes. See setrlimit(2) for details on the resource limit
concept. Resource limits may be specified in two formats: either as single
value to set a specific soft and hard limit to the same value, or as
colon-separated pair soft:hard to set both limits individually (e.g.
"LimitAS=4G:16G"). Use the string infinity to configure no
limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E
(to the base 1024) may be used for resource limits measured in bytes (e.g.
LimitAS=16G). For the limits referring to time values, the usual time units
ms, s, min, h and so on may be used (see systemd.time(7) for details).
Note that if no time unit is specified for LimitCPU= the default unit
of seconds is implied, while for LimitRTTIME= the default unit of
microseconds is implied. Also, note that the effective granularity of the
limits might influence their enforcement. For example, time limits specified
for LimitCPU= will be rounded up implicitly to multiples of 1s. For
LimitNICE= the value may be specified in two syntaxes: if prefixed with
"+" or "-", the value is understood as regular Linux nice
value in the range -20..19. If not prefixed like this the value is understood
as raw resource limit parameter in the range 0..40 (with 0 being equivalent to
1).
Note that most process resource limits configured with these options are
per-process, and processes may fork in order to acquire a new set of resources
that are accounted independently of the original process, and may thus escape
limits set. Also note that LimitRSS= is not implemented on Linux, and
setting it has no effect. Often it is advisable to prefer the resource
controls listed in systemd.resource-control(5) over these per-process
limits, as they apply to services as a whole, may be altered dynamically at
runtime, and are generally more expressive. For example, MemoryLimit=
is a more powerful (and working) replacement for LimitRSS=.
Table 1. Limit directives and their equivalent with ulimit
PAMName=
Directive | ulimit equivalent | Unit |
LimitCPU= | ulimit -t | Seconds |
LimitFSIZE= | ulimit -f | Bytes |
LimitDATA= | ulimit -d | Bytes |
LimitSTACK= | ulimit -s | Bytes |
LimitCORE= | ulimit -c | Bytes |
LimitRSS= | ulimit -m | Bytes |
LimitNOFILE= | ulimit -n | Number of File Descriptors |
LimitAS= | ulimit -v | Bytes |
LimitNPROC= | ulimit -u | Number of Processes |
LimitMEMLOCK= | ulimit -l | Bytes |
LimitLOCKS= | ulimit -x | Number of Locks |
LimitSIGPENDING= | ulimit -i | Number of Queued Signals |
LimitMSGQUEUE= | ulimit -q | Bytes |
LimitNICE= | ulimit -e | Nice Level |
LimitRTPRIO= | ulimit -r | Realtime Priority |
LimitRTTIME= | No equivalent | Microseconds |
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.
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), e.g. CAP_SYS_ADMIN, CAP_DAC_OVERRIDE,
CAP_SYS_PTRACE. 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 affects the respective
capabilities in the effective, permitted and inheritable capability sets. 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 "~" (without any further argument), the bounding
set is reset to the full set of available capabilities, also undoing any
previous settings.
AmbientCapabilities=
Controls which capabilities to include in the ambient
capability set for the executed process. Takes a whitespace-separated list of
capability names as read by cap_from_name(3), e.g.
CAP_SYS_ADMIN, CAP_DAC_OVERRIDE, CAP_SYS_PTRACE. This
option may appear more than once in which case the ambient capability sets are
merged. If the list of capabilities is prefixed with "~", all but
the listed capabilities will be included, the effect of the assignment
inverted. If the empty string is assigned to this option, the ambient
capability set is reset to the empty capability set, and all prior settings
have no effect. If set to "~" (without any further argument), the
ambient capability set is reset to the full set of available capabilities,
also undoing any previous settings. Note that adding capabilities to ambient
capability set adds them to the process's inherited capability set.
Ambient capability sets are useful if you want to execute a process as a
non-privileged user but still want to give it some capabilities. Note that in
this case option keep-caps is automatically added to SecureBits=
to retain the capabilities over the user change.
SecureBits=
Controls the secure bits set for the executed process.
Takes a space-separated combination of options from the following list:
keep-caps, keep-caps-locked, no-setuid-fixup,
no-setuid-fixup-locked, noroot, and noroot-locked. 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. See
capabilities(7) for details.
ReadWriteDirectories=, ReadOnlyDirectories=,
InaccessibleDirectories=
Sets up a new file system namespace 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, and may not countain
any other mountpoints, including those specified by
ReadWriteDirectories= or ReadOnlyDirectories=. Note that
restricting access with these options does not extend to submounts of a
directory that are created later on. 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.
Paths in ReadOnlyDirectories= and InaccessibleDirectories= may be
prefixed with "-", in which case they will be ignored when they do
not exist. Note that using this setting will disconnect propagation of mounts
from the service to the host (propagation in the opposite direction continues
to work). This means that this setting may not be used for services which
shall be able to install mount points in the main mount namespace.
PrivateTmp=
Takes a boolean argument. If true, sets up a new file
system namespace for the executed processes and mounts private /tmp and
/var/tmp 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 /tmp or /var/tmp impossible. If this
is enabled, all temporary files created by a service in these directories will
be removed after the service is stopped. Defaults to false. It is possible to
run two or more units within the same private /tmp and /var/tmp namespace by
using the JoinsNamespaceOf= directive, see systemd.unit(5) for
details. Note that using this setting will disconnect propagation of mounts
from the service to the host (propagation in the opposite direction continues
to work). This means that this setting may not be used for services which
shall be able to install mount points in the main mount namespace.
PrivateDevices=
Takes a boolean argument. If true, sets up a new /dev
namespace for the executed processes and only adds API pseudo devices such as
/dev/null, /dev/zero or /dev/random (as well as the pseudo TTY subsystem) to
it, but no physical devices such as /dev/sda. This is useful to securely turn
off physical device access by the executed process. Defaults to false.
Enabling this option will also remove CAP_MKNOD from the capability
bounding set for the unit (see above), and set DevicePolicy=closed (see
systemd.resource-control(5) for details). Note that using this setting
will disconnect propagation of mounts from the service to the host
(propagation in the opposite direction continues to work). This means that
this setting may not be used for services which shall be able to install mount
points in the main mount namespace. The /dev namespace will be mounted
read-only and 'noexec'. The latter may break old programs which try to set up
executable memory by using mmap(2) of /dev/zero instead of using
MAP_ANON.
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. It is possible to run two or more
units within the same private network namespace by using the
JoinsNamespaceOf= directive, see systemd.unit(5) for details.
Note that this option will disconnect all socket families from the host, this
includes AF_NETLINK and AF_UNIX. The latter has the effect that AF_UNIX
sockets in the abstract socket namespace will become unavailable to the
processes (however, those located in the file system will continue to be
accessible).
ProtectSystem=
Takes a boolean argument or "full". If true,
mounts the /usr and /boot directories read-only for processes invoked by this
unit. If set to "full", the /etc directory is mounted read-only,
too. This setting ensures that any modification of the vendor-supplied
operating system (and optionally its configuration) is prohibited for the
service. It is recommended to enable this setting for all long-running
services, unless they are involved with system updates or need to modify the
operating system in other ways. Note however that processes retaining the
CAP_SYS_ADMIN capability can undo the effect of this setting. This setting is
hence particularly useful for daemons which have this capability removed, for
example with CapabilityBoundingSet=. Defaults to off.
ProtectHome=
Takes a boolean argument or "read-only". If
true, the directories /home, /root and /run/user are made inaccessible and
empty for processes invoked by this unit. If set to "read-only", the
three directories are made read-only instead. It is recommended to enable this
setting for all long-running services (in particular network-facing ones), to
ensure they cannot get access to private user data, unless the services
actually require access to the user's private data. Note however that
processes retaining the CAP_SYS_ADMIN capability can undo the effect of this
setting. This setting is hence particularly useful for daemons which have this
capability removed, for example with CapabilityBoundingSet=. Defaults
to off.
MountFlags=
Takes a mount propagation flag: shared,
slave or private, which control whether mounts in the file
system namespace set up for this unit's processes will receive or propagate
mounts or unmounts. See mount(2) for details. Defaults to
shared. Use shared to ensure that mounts and unmounts are
propagated from the host to the container and vice versa. Use slave to
run processes so that none of their mounts and unmounts will propagate to the
host. Use private to also ensure that no mounts and unmounts from the
host will propagate into the unit processes' namespace. Note that slave
means that file systems mounted on the host might stay mounted continuously in
the unit's namespace, and thus keep the device busy. Note that the file system
namespace related options ( PrivateTmp=, PrivateDevices=,
ProtectSystem=, ProtectHome=, ReadOnlyDirectories=,
InaccessibleDirectories= and ReadWriteDirectories=) require that
mount and unmount propagation from the unit's file system namespace is
disabled, and hence downgrade shared to slave.
UtmpIdentifier=
Takes a four character identifier string for an
utmp(5) and wtmp entry for this service. This should only be set for
services such as getty implementations (such as agetty(8)) where
utmp/wtmp entries must be created and cleared before and after execution, or
for services that shall be executed as if they were run by a getty
process (see below). 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.
UtmpMode=
Takes one of "init", "login" or
"user". If UtmpIdentifier= is set, controls which type of
utmp(5)/wtmp entries for this service are generated. This setting has
no effect unless UtmpIdentifier= is set too. If "init" is
set, only an INIT_PROCESS entry is generated and the invoked process
must implement a getty-compatible utmp/wtmp logic. If "login"
is set, first an INIT_PROCESS entry, followed by a LOGIN_PROCESS
entry is generated. In this case, the invoked process must implement a
login(1)-compatible utmp/wtmp logic. If "user" is set, first
an INIT_PROCESS entry, then a LOGIN_PROCESS entry and finally a
USER_PROCESS entry is generated. In this case, the invoked process may
be any process that is suitable to be run as session leader. Defaults to
"init".
SELinuxContext=
Set the SELinux security context of the executed process.
If set, this will override the automated domain transition. However, the
policy still needs to authorize the transition. This directive is ignored if
SELinux is disabled. If prefixed by "-", all errors will be ignored.
See setexeccon(3) for details.
AppArmorProfile=
Takes a profile name as argument. The process executed by
the unit will switch to this profile when started. Profiles must already be
loaded in the kernel, or the unit will fail. This result in a non operation if
AppArmor is not enabled. If prefixed by "-", all errors will be
ignored.
SmackProcessLabel=
Takes a SMACK64 security label as argument. The
process executed by the unit will be started under this label and SMACK will
decide whether the process is allowed to run or not, based on it. The process
will continue to run under the label specified here unless the executable has
its own SMACK64EXEC label, in which case the process will transition to
run under that label. When not specified, the label that systemd is running
under is used. This directive is ignored if SMACK is disabled.
The value may be prefixed by "-", in which case all errors will be
ignored. An empty value may be specified to unset previous assignments.
IgnoreSIGPIPE=
Takes a boolean argument. If true, causes SIGPIPE
to be ignored in the executed process. Defaults to true because SIGPIPE
generally is useful only in shell pipelines.
NoNewPrivileges=
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.
SystemCallFilter=
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
SIGSYS signal (whitelisting). If the first character of the list is
"~", the effect is inverted: only the listed system calls will
result in immediate process termination (blacklisting). If running in user
mode, or in system mode, but without the CAP_SYS_ADMIN capabiblity
(e.g. setting User=nobody), NoNewPrivileges=yes 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 execve, rt_sigreturn,
sigreturn, exit_group, exit 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.
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. (For example, if
you have started with a whitelisting of read and write, and
right after it add a blacklisting of write, then write will be
removed from the set.)
SystemCallErrorNumber=
Takes an "errno" error number name to return
when the system call filter configured with SystemCallFilter= is
triggered, instead of terminating the process immediately. Takes an error name
such as EPERM, EACCES or EUCLEAN. When this setting is
not used, or when the empty string is assigned, the process will be terminated
immediately when the filter is triggered.
SystemCallArchitectures=
Takes a space-separated list of architecture identifiers
to include in the system call filter. The known architecture identifiers are
x86, x86-64, x32, arm as well as the special
identifier native. 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 32-bit x86 binaries on 64-bit x86-64 systems. The
special native identifier implicitly maps to the native architecture of
the system (or more strictly: to the architecture the system manager is
compiled for). If running in user mode, or in system mode, but without the
CAP_SYS_ADMIN capabiblity (e.g. setting User=nobody),
NoNewPrivileges=yes is implied. Note that setting this option to a
non-empty list implies that native is included too. By default, this
option is set to the empty list, i.e. no architecture system call filtering is
applied.
RestrictAddressFamilies=
Restricts the set of socket address families accessible
to the processes of this unit. Takes a space-separated list of address family
names to whitelist, such as AF_UNIX, AF_INET or AF_INET6.
When prefixed with ~ the listed address families will be applied as
blacklist, otherwise as whitelist. Note that this restricts access to the
socket(2) system call only. Sockets passed into the process by other
means (for example, by using socket activation with socket units, see
systemd.socket(5)) are unaffected. Also, sockets created with
socketpair() (which creates connected AF_UNIX sockets only) are
unaffected. Note that this option has no effect on 32-bit x86 and is ignored
(but works correctly on x86-64). If running in user mode, or in system mode,
but without the CAP_SYS_ADMIN capabiblity (e.g. setting
User=nobody), NoNewPrivileges=yes is implied. By default, no
restriction applies, all address families are accessible to processes. If
assigned the empty string, any previous list changes are undone.
Use this option to limit exposure of processes to remote systems, in particular
via exotic network protocols. Note that in most cases, the local
AF_UNIX address family should be included in the configured whitelist
as it is frequently used for local communication, including for
syslog(2) logging.
Personality=
Controls which kernel architecture uname(2) shall
report, when invoked by unit processes. Takes one of the architecture
identifiers x86, x86-64, ppc, ppc-le,
ppc64, ppc64-le, s390 or s390x. Which personality
architectures are supported depends on the system architecture. Usually the
64bit versions of the various system architectures support their immediate
32bit personality architecture counterpart, but no others. For example,
x86-64 systems support the x86-64 and x86 personalities
but no others. The personality feature is useful when running 32-bit services
on a 64-bit host system. If not specified, the personality is left unmodified
and thus reflects the personality of the host system's kernel.
RuntimeDirectory=, RuntimeDirectoryMode=
Takes a list of directory names. If set, one or more
directories by the specified names will be created below /run (for system
services) or below $XDG_RUNTIME_DIR (for user services) when the unit
is started, and removed when the unit is stopped. The directories will have
the access mode specified in RuntimeDirectoryMode=, and will be owned
by the user and group specified in User= and Group=. Use this to
manage one or more runtime directories of the unit and bind their lifetime to
the daemon runtime. The specified directory names must be relative, and may
not include a "/", i.e. must refer to simple directories to create
or remove. This is particularly useful for unprivileged daemons that cannot
create runtime directories in /run due to lack of privileges, and to make sure
the runtime directory is cleaned up automatically after use. For runtime
directories that require more complex or different configuration or lifetime
guarantees, please consider using tmpfiles.d(5).
ENVIRONMENT VARIABLES IN SPAWNED PROCESSES¶
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. $PATHColon-separated list of directories to use when launching
executables. Systemd uses a fixed value of
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin.
$LANG
Locale. Can be set in locale.conf(5) or on the
kernel command line (see systemd(1) and
kernel-command-line(7)).
$USER, $LOGNAME, $HOME, $SHELL
User name (twice), home directory, and the login shell.
The variables are set for the units that have User= set, which includes
user systemd instances. See passwd(5).
$XDG_RUNTIME_DIR
The directory for volatile state. Set for the user
systemd instance, and also in user sessions. See
pam_systemd(8).
$XDG_SESSION_ID, $XDG_SEAT, $XDG_VTNR
The identifier of the session, the seat name, and virtual
terminal of the session. Set by pam_systemd(8) for login sessions.
$XDG_SEAT and $XDG_VTNR will only be set when attached to a seat
and a tty.
$MAINPID
The PID of the units main process if it is known. This is
only set for control processes as invoked by ExecReload= and
similar.
$MANAGERPID
The PID of the user systemd instance, set for
processes spawned by it.
$LISTEN_FDS, $LISTEN_PID, $LISTEN_FDNAMES
Information about file descriptors passed to a service
for socket activation. See sd_listen_fds(3).
$NOTIFY_SOCKET
The socket sd_notify() talks to. See
sd_notify(3).
$WATCHDOG_PID, $WATCHDOG_USEC
Information about watchdog keep-alive notifications. See
sd_watchdog_enabled(3).
$TERM
Terminal type, set only for units connected to a terminal
( StandardInput=tty, StandardOutput=tty, or
StandardError=tty). See termcap(5).
Additional variables may be configured by the following means: for processes
spawned in specific units, use the Environment=,
EnvironmentFile= and PassEnvironment= options above; to specify
variables globally, use DefaultEnvironment= (see
systemd-system.conf(5)) or the kernel option systemd.setenv=
(see systemd(1)). Additional variables may also be set through PAM,
cf. pam_env(8).
SEE ALSO¶
systemd(1), systemctl(1), journalctl(8), systemd.unit(5), systemd.service(5), systemd.socket(5), systemd.swap(5), systemd.mount(5), systemd.kill(5), systemd.resource-control(5), systemd.time(7), systemd.directives(7), tmpfiles.d(5), exec(3)NOTES¶
- 1.
- proc.txt
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