USER@.SERVICE(5) user@.service USER@.SERVICE(5)
NAME
user@.service, user-runtime-dir@.service - System units to manage user
processes
SYNOPSIS
user@UID.service
user-runtime-dir@UID.service
user-UID.slice
DESCRIPTION
The systemd(1) system manager (PID 1) starts user manager instances as
user@UID.service, where the user's numerical UID is used as the
instance identifier. Each systemd --user instance manages a hierarchy
of its own units. See systemd(1) for a discussion of systemd units and
systemd.special(1) for a list of units that form the basis of the unit
hierarchies of system and user units.
user@UID.service is accompanied by the system unit
user-runtime-dir@UID.service, which creates the user's runtime
directory /run/user/UID, and then removes it when this unit is stopped.
User processes may be started by the user@.service instance, in which
case they will be part of that unit in the system hierarchy. They may
also be started elsewhere, for example by sshd(8) or a display manager
like gdm, in which case they form a .scope unit (see systemd.scope(5)).
Both user@UID.service and the scope units are collected under a
user-UID.slice.
Individual user-UID.slice slices are collected under user.slice, see
systemd.special(8).
CONTROLLING RESOURCES FOR LOGGED-IN USERS
Options that control resources available to logged-in users can be
configured at a few different levels. As described in the previous
section, user.slice contains processes of all users, so any resource
limits on that slice apply to all users together. The usual way to
configure them would be through drop-ins, e.g.
/etc/systemd/system/user.slice.d/resources.conf.
The processes of a single user are collected under user-UID.slice.
Resource limits for that user can be configured through drop-ins for
that unit, e.g. /etc/systemd/system/user-1000.slice.d/resources.conf.
If the limits should apply to all users instead, they may be configured
through drop-ins for the truncated unit name, user-.slice. For example,
configuration in /etc/systemd/system/user-.slice.d/resources.conf is
included in all user-UID.slice units, see systemd.unit(5) for a
discussion of the drop-in mechanism.
When a user logs in and a .scope unit is created for the session (see
previous section), the creation of the scope may be managed through
pam_systemd(8). This PAM module communicates with systemd-logind(8) to
create the session scope and provide access to hardware resources.
Resource limits for the scope may be configured through the PAM module
configuration, see pam_systemd(8). Configuring them through the normal
unit configuration is also possible, but since the name of the slice
unit is generally unpredictable, this is less useful.
In general any resources that apply to units may be set for
user@UID.service and the slice units discussed above, see
systemd.resource-control(5) for an overview.
EXAMPLES
Example 1. Hierarchy of control groups with two logged in users
$ systemd-cgls
Control group /:
-.slice
user.slice
| user-1000.slice
| | user@1000.service
| | | pulseaudio.service
| | | | 2386 /usr/bin/pulseaudio --daemonize=no
| | | gnome-terminal-server.service
| | | init.scope
| | | 4127 /libexec/gnome-terminal-server
| | | 4198 zsh
| | ...
| | session-4.scope
| | 1264 gdm-session-worker [pam/gdm-password]
| | 2339 /usr/bin/gnome-shell
| | ...
| | session-19.scope
| | 6497 sshd: zbyszek [priv]
| | 6502 sshd: zbyszek@pts/6
| | 6509 -zsh
| | 6602 systemd-cgls --no-pager
| ...
| user-1001.slice
| session-20.scope
| | 6675 sshd: guest [priv]
| | 6708 sshd: guest@pts/6
| | 6717 -bash
| user@1001.service
| init.scope
| | 6680 /lib/systemd/systemd --user
| | 6688 (sd-pam)
| sleep.service
| 6706 /usr/bin/sleep 30
...
User with UID 1000 is logged in using gdm (session-4.scope) and ssh(1)
(session-19.scope), and also has a user manager instance running
(user@1000.service). User with UID 1001 is logged in using ssh
(session-20.scope) and also has a user manager instance running
(user@1001.service). Those are all (leaf) system units, and form part
of the slice hierarchy, with user-1000.slice and user-1001.slice below
user.slice. User units are visible below the user@.service instances
(pulseaudio.service, gnome-terminal-server.service, init.scope,
sleep.service).
Example 2. Default user resource limits
$ systemctl cat user-1000.slice
# /lib/systemd/system/user-.slice.d/10-defaults.conf
# ...
[Unit]
Description=User Slice of UID %j
After=systemd-user-sessions.service
[Slice]
TasksMax=33%
The user-UID.slice units by default don't have a unit file. The
resource limits are set through a drop-in, which can be easily replaced
or extended following standard drop-in mechanisms discussed in the
first section.
SEE ALSO
systemd(1), systemd.service(5), systemd.slice(5), systemd.resource-
control(5), systemd.exec(5), systemd.special(7), pam(8)
systemd 245 USER@.SERVICE(5)