systemd/User

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Revision as of 05:51, 20 December 2012 by KaiSforza (Talk | contribs) (Using systemd --user To Manage Your Session)

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Summary help replacing me
Covers how to set up systemd user sessions.
Related
systemd

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

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.

I began using gtmanfred's guide to setting this up. I rewrote it partially to be of more help, and partially to help get this into my head even more.

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-helperAUR and user-session-unitsAUR.

Next is setting up your targets. I set up two, one for my window manager (i3) and another as a default target. The window manager target, i3wm.target as I called it, should be populated like so:

[Unit]
Description=i3wm
Wants=xorg.target
Wants=myStuff.target
Requires=dbus.socket
AllowIsolate=true

[Install]
Alias=default.target

This will be the target for your graphical interface. (Replace i3wm with your choice of window manager/desktop environment.)

I put together a second target called mystuff.target. This will be 'WantedBy' all services but your window manager:

[Unit]
Description=Xinitrc Stuff
Wants=i3wm.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. I named mine i3.service:

[Unit]
Description=i3wm
Before=mystuff.target
After=xorg.target

[Service]
Requires=xorg.target
Environment=PATH=/home/wgiokas/.cabal/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/home/wgiokas/bin
Environment=DISPLAY=:0
ExecStart=/usr/bin/i3
Restart=always
RestartSec=10

[Install]
WantedBy=i3wm.target

Note the [Install] section includes a 'WantedBy' part. When using systemctl --user enable it will link this as $HOME/.config/systemd/user/i3wm.target.wants/i3.service, allowing it to be started at login. I would recommend enabling this service, not linking it manually.

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

Doing this will not allow you to run systemd --user, though. If you installed user-session-units as listed above, then you must copy user-session@.service to your user unit directory and use systemctl --user enable user-session@yourloginname.service (replace the obvious). Next, edit the user-session@.service (not the user-session@yourloginname.service) and edit this line:

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

to this: (Note the subtle change where the %I become %U)

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

You will need to patch systemd to do this, so either using systemd-git from after commit 067d851d or patch it into systemd with the ABS.

Last but not least, add this line to /etc/pam.d/login or /etc/pam.d/systemd-auth (whichever exists):

session    required    pam_systemd.so

Now add /usr/lib/systemd/systemd --user to your shell's $HOME/.*profile file and you are ready to go! (This takes a lot of tweaking, so when I say that, I mean that you are ready to debug and find spelling mistakes.)

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. I would recommend starting with systemd.unit(5).

Once all of this is up and running, you can type systemctl --user status i3.service (or whatever your window manager or desktop environment is called) and see something like this:

i3.service - i3wm
	  Loaded: loaded (/home/wgiokas/.config/systemd/user/i3.service; enabled)
	  Active: active (running) since Wed 2012-12-19 20:28:24 CST; 3h 8min ago
	Main PID: 11115 (i3)
	  CGroup: name=systemd:/user/wgiokas/3/systemd-11047/i3.service
		  ├─11115 /usr/bin/i3
		  ├─11127 i3bar --bar_id=bar-tyxnbu --socket=/run/user/1000/i3/ipc-socket.11115
		  ├─11133 i3status -c /home/wgiokas/.i3/status.conf
		  ├─27069 /bin/zsh
		  ├─27088 luakit
		  ├─29306 /bin/zsh
		  └─29317 dwb

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 before the exec line:

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.

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 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:

[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.

External links