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(7) 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(7).

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)