Difference between revisions of "Systemd/User"

Revision as of 23:16, 26 April 2013

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systemd offers users the ability to run an instance of systemd to manage their session and services. This allows users to start, stop, enable, and disable units found within certain directories when systemd is run by the user. This is convenient for daemons and other services that are commonly run as a user other than root or a special user, such as mpd.

Setup

startx

Users should first set up systemd-logind to manage their session. If systemd is running as the system init daemon, then this is already happening.

Next, the user must launch systemd by putting the following in their ~/.xinitrc.

systemd --user

systemd --user &

After starting X, the user can check whether their session is now being managed by systemd-logind with the following command:

$ loginctl --no-pager show-session $XDG_SESSION_ID | grep Active

If this command prints Active=yes, then the user is now using systemd-logind to manage their session. The user should remove any instances of ck-launch-session or dbus-launch from their ~/.xinitrc, as those commands are unneeded.

Display Managers

All of the major display managers are now using systemd-logind by default, so the loginctl command from the previous section should work as stated. A user simply has to add systemd --user as a program to be started by their desktop environment.

GNOME 3 (using GDM)

For users who wish to have GDM/GNOME 3 auto-start their systemd --user session upon login, they just need to add a special log in session for this:

/usr/share/xsessions/gnome-systemd.desktop

[Desktop Entry]
Type=Application
Name=systemd
Comment=Runs 'systemd' as a user instance.
Exec=/usr/lib/systemd/systemd --user

Make sure to choose the systemd session option at the GDM login screen.

Using systemd --user To Manage Your Session

Systemd has many amazing features, one of which is the ability to track programs using cgroups (by running systemctl status). While awesome for a pid 1 process to do, it is also extremely useful for users, and having it set up and initialize user programs, all the while tracking what is in each cgroup is even more amazing.

All of your systemd user units will go to $HOME/.config/systemd/user. These units take precedence over units in other systemd unit directories.

There are two packages you need to get this working, both currently available from the AUR: xorg-launch-helper^AUR and optionally, user-session-units^AUR if you want to have autologin working.

Next is setting up your targets. You should set up two, one for window manager and another as a default target. The window manager target should be populated like so:

$HOME/.config/systemd/user/wm.target

[Unit]
Description=Window manager target
Wants=xorg.target
Wants=mystuff.target
Requires=dbus.socket
AllowIsolate=true

[Install]
Alias=default.target

This will be the target for your graphical interface.

Put together a second target called mystuff.target. All services but your window manager should contain a WantedBy line, under [Install], pointing at this unit.

$HOME/.config/systemd/user/mystuff.target

[Unit]
Description=Xinitrc Stuff
Wants=wm.target

[Install]
Alias=default.target

Link this unit to default.target. When you start systemd --user, it will start this target.

Next you need to begin writing services. First you should throw together a service for your window manager:

$HOME/.config/systemd/user/YOUR_WM.service

[Unit]
Description=your window manager service
Before=mystuff.target
After=xorg.target
Requires=xorg.target

[Service]
#Environment=PATH=uncomment:to:override:your:PATH
ExecStart=/full/path/to/wm/executable
Restart=always
RestartSec=10
 
[Install]
WantedBy=wm.target

You can fill your user unit directory with a plethora of services, including ones for mpd, gpg-agent, offlineimap, parcellite, pulse, tmux, urxvtd, xbindkeys and xmodmap to name a few.

Auto-login

If you want to have systemd automatically log you in on boot, then you can use the unit in user-session-units to do so. Enabling a screen locker for will stop someone from booting your computer into a nice, logged in session.

If you installed user-session-units as listed above, then you must copy /usr/lib/systemd/system/user-session@.service to /etc/systemd/system/user-session@yourloginname.service) and edit these lines:

Environment=XDG_RUNTIME_DIR=/run/user/%I
Environment=DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/%I/dbus/user_bus_socket

to this:

Environment=XDG_RUNTIME_DIR=/run/user/%U
Environment=DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/%U/dbus/user_bus_socket

As well as an install section:

[Install]
WantedBy=graphical.target

or if you have no login manager:

[Install]
WantedBy=getty.target

Add this line to /etc/pam.d/login and /etc/pam.d/system-auth:

session    required    pam_systemd.so

Because user-session@.service starts on tty1, you will need to add Conflicts=getty@tty1.service to the service file, if it doesn't exist already. Alternately, you can have it run on tty7 instead by modifying TTYPath accordingly as well as the ExecStart line in xorg.service (cp /usr/lib/systemd/user/xorg.service /etc/systemd/user/ and make the modifications there).

Once this is done, systemctl --user enable YOUR_WM.service

One of the most important things you can add to the service files you will be writing is the use of Before= and After= in the [Unit] section. These two parts will determine the order things are started. Say you have a graphical application you want to start on boot, you would put After=xorg.target into your unit. Say you start ncmpcpp, which requires mpd to start, you can put After=mpd.service into your ncmpcpp unit. You will eventually figure out exactly how this needs to go either from experience or from reading the systemd manual pages. Starting with systemd.unit(5) is a good idea.

Other use cases

Persistent terminal multiplexer

You may wish your user session to default to running a terminal multiplexer, such as GNU Screen or Tmux, in the background rather than logging you into a window manager session. Separating login from X login is most likely only useful for those who boot to a TTY instead of to a display manager (in which case you can simply bundle everything you start in with myStuff.target).

To create this type of user session, procede as above, but instead of creating wm.target, create multiplexer.target:

[Unit]
Description=Terminal multiplexer
Documentation=info:screen man:screen(1) man:tmux(1)
After=cruft.target
Wants=cruft.target

[Install]
Alias=default.target

cruft.target, like mystuff.target above, should start anything you think should run before tmux or screen starts (or which you want started at boot regardless of timing), such as a GnuPG daemon session.

You then need to create a service for your multiplexer session. Here is a sample service, using tmux as an example and sourcing a gpg-agent session which wrote its information to /tmp/gpg-agent-info. This sample session, when you start X, will also be able to run X programs, since DISPLAY is set.

[Unit]
Description=tmux: A terminal multiplixer Documentation=man:tmux(1)
After=gpg-agent.service
Wants=gpg-agent.service

[Service]
Type=forking
ExecStart=/usr/bin/tmux start
ExecStop=/usr/bin/tmux kill-server
Environment=DISPLAY=:0
EnvironmentFile=/tmp/gpg-agent-info

[Install]
WantedBy=multiplexer.target

Once this is done, systemctl --user enable tmux.service, multiplexer.target and any services you created to be run by cruft.target and you should be set to go! Activated user-session@.service as described above, but be sure to remove the Conflicts=getty@tty1.service from user-session@.service, since your user session will not be taking over a TTY. Congratulations! You have a running terminal multiplexer and some other useful programs ready to start at boot!

Starting X

You have probably noticed that, since the terminal multiplexer is now default.target, X will not start automatically at boot. To start X, proceed as above, but do not activate or manually link to default.target wm.target. Instead, assuming you are booting to a terminal, we will simply be using a hack-ish workaround and masking /usr/bin/startx with a shell alias:

alias startx='systemctl --user start wm.target'

User Services

Users may now interact with units located in the following directories just as they would with system services (ordered by ascending precedence):

• /usr/lib/systemd/user/
• /etc/systemd/user/
• ~/.config/systemd/user/

To control the systemd instance, the user must use the command systemctl --user.

Installed by packages

A unit installed by a package that is meant to be run by a systemd user instance should install the unit to /usr/lib/systemd/user/. The system adminstration can then modify the unit by copying it to /etc/systemd/user/. A user can then modify the unit by copying it to ~/.config/systemd/user/.

Example

The following is an example of a user version of the mpd service.

mpd.service

[Unit]
Description=Music Player Daemon

[Service]
ExecStart=/usr/bin/mpd --no-daemon

[Install]
WantedBy=default.target

Example with variables

The following is an example of a user version of sickbeard.service, which takes into account variable home directories where SickBeard can find certain files:

sickbeard.service

[Unit]
Description=SickBeard Daemon

[Service]
ExecStart=/usr/bin/env python2 /opt/sickbeard/SickBeard.py --config %h/.sickbeard/config.ini --datadir %h/.sickbeard

[Install]
WantedBy=default.target

As detailed in man systemd.unit, the %h variable is replaced by the home directory of the user running the service. There are other variables that can be taken into account in the systemd manpages.

Note about X applications

Most X apps need a DISPLAY variable to run (so it's likely the first reason why your service files aren't starting), so you have to make sure to include it:

$HOME/.config/systemd/user/parcellite.service

[Unit]
Description=Parcellite clipboard manager

[Service]
ExecStart=/usr/bin/parcellite
Environment=DISPLAY=:0 # <= !

[Install]
WantedBy=mystuff.target

A simpler way, if using user-session-units^AUR, is to define it in user-session@yourloginname.service so it's inherited. Add Environment=DISPLAY=:0 to the [Service] section. Another helpful environment variable to set here is SHELL.

A cleaner way though, is to not hard code the DISPLAY environment variable (specially if you run more than on display):

$HOME/.config/systemd/user/x-app-template@.service

[Unit]
Description=Your amazing and original description

[Service]
ExecStart=/full/path/to/the/app
Environment=DISPLAY=%i # <= !

[Install]
WantedBy=mystuff.target

Then you can run it with:

systemctl --user {start|enable} x-app@your-desired-display.service # <= :0 in most cases

See also

• gtmanfred's guide - the original guideTemplate:Linkrot
• KaiSforza's bitbucket wiki
• Collection of useful systemd user units
• More systemd user units