systemd.scope — Scope unit configuration
scope.scope
Scope units are not configured via unit configuration files,
but are only created programmatically using the bus interfaces of
systemd. They are named similar to filenames. A unit whose name
ends in ".scope" refers to a scope unit. Scopes
units manage a set of system processes. Unlike service units, scope
units manage externally created processes, and do not fork off
processes on its own.
The main purpose of scope units is grouping worker processes of a system service for organization and for managing resources.
systemd-run --scope may
be used to easily launch a command in a new scope unit from the
command line.
See the New Control Group Interfaces for an introduction on how to make use of scope units from programs.
Note that, unlike service units, scope units have no "main" process: all processes in the scope are equivalent. The lifecycle of the scope unit is thus not bound to the lifetime of one specific process, but to the existence of at least one process in the scope. This also means that the exit statuses of these processes are not relevant for the scope unit failure state. Scope units may still enter a failure state, for example due to resource exhaustion or stop timeouts being reached, but not due to programs inside of them terminating uncleanly. Since processes managed as scope units generally remain children of the original process that forked them off, it is also the job of that process to collect their exit statuses and act on them as needed.
Implicit dependencies may be added as result of resource control parameters as documented in systemd.resource-control(5).
The following dependencies are added unless
DefaultDependencies=no is set:
Scope units will automatically have dependencies of
type Conflicts= and
Before= on
shutdown.target. These ensure
that scope units are removed prior to system
shutdown. Only scope units involved with early boot or
late system shutdown should disable
DefaultDependencies= option.
Scope files may include a [Unit] section, which is described in systemd.unit(5).
Scope files may include a [Scope] section, which carries information about the scope and the units it contains. A number of options that may be used in this section are shared with other unit types. These options are documented in systemd.kill(5) and systemd.resource-control(5). The options specific to the [Scope] section of scope units are the following:
OOMPolicy=¶Configure the out-of-memory (OOM) killing policy for the kernel and the userspace OOM
killer
systemd-oomd.service(8).
On Linux, when memory becomes scarce to the point that the kernel has trouble allocating memory for
itself, it might decide to kill a running process in order to free up memory and reduce memory
pressure. Note that systemd-oomd.service is a more flexible solution that aims
to prevent out-of-memory situations for the userspace too, not just the kernel, by attempting to
terminate services earlier, before the kernel would have to act.
This setting takes one of continue, stop or
kill. If set to continue and a process in the unit is
killed by the OOM killer, this is logged but the unit continues running. If set to
stop the event is logged but the unit is terminated cleanly by the service
manager. If set to kill and one of the unit's processes is killed by the OOM
killer the kernel is instructed to kill all remaining processes of the unit too, by setting the
memory.oom.group attribute to 1; also see kernel
page Control Group v2.
Defaults to the setting DefaultOOMPolicy= in
systemd-system.conf(5)
is set to, except for units where Delegate= is turned on, where it defaults to
continue.
Use the OOMScoreAdjust= setting to configure whether processes of the unit
shall be considered preferred or less preferred candidates for process termination by the Linux OOM
killer logic. See
systemd.exec(5) for
details.
This setting also applies to systemd-oomd.service(8). Similarly to the kernel OOM kills performed by the kernel, this setting determines the state of the unit after systemd-oomd kills a cgroup associated with it.
RuntimeMaxSec=¶Configures a maximum time for the scope to run. If this is used and the scope has been
active for longer than the specified time it is terminated and put into a failure state. Pass
"infinity" (the default) to configure no runtime limit.
RuntimeRandomizedExtraSec=¶This option modifies RuntimeMaxSec= by increasing the maximum runtime by an
evenly distributed duration between 0 and the specified value (in seconds). If RuntimeMaxSec= is
unspecified, then this feature will be disabled.
Check systemd.unit(5), systemd.exec(5), and systemd.kill(5) for more settings.