user@.service - Man Page

user@UID​.service

user-runtime-dir@UID​.service

/usr/lib/systemd/systemd-user-runtime-dir

user-UID​.slice

The systemd(1) system manager (PID 1) starts user manager instances as user@UID​.service, with the user's numerical UID used as the instance identifier​. These instances use the same executable as the system manager, but running in a mode where it starts a different set of units​. Each systemd --user instance manages a hierarchy of units specific to that user​. See systemd(1) for a discussion of 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 when started, and removes it when it is stopped​. It also might apply runtime quota settings on /tmp/ and/or /dev/shm/ for the user​. user-runtime-dir@UID​.service executes the systemd-user-runtime-dir binary to do the actual work​.

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 the user-UID​.slice​.

Individual user-UID​.slice slices are collected under user​.slice, see systemd.special(7)​.

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​.

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 /usr/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 /usr/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
# /usr/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 do not 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​.

systemd(1), systemd.service(5), systemd.slice(5), systemd.resource-control(5), systemd.exec(5), systemd.special(7), capsule@.service(5), pam(8)