User Systemd Services

The systemd manager allows configuring services from a normal system user. These systemd user services are a little-known but very useful feature. It consists of being able to create and use .service files from a user’s local directory that run with their privileges.

systemd is a system and service manager for Linux that runs as PID 1 and boots the entire system. It enables parallelization, uses sockets and D-Bus to start services, launches daemons, monitors and manages processes and mount points. It displaced sysvinit as the de facto standard some time ago.

It has a very interesting feature called “user lingering” which consists of running systemd instances as a normal system user. This will allow us to launch user processes during system boot.

Configuration

Let’s look at an example. I have a virtual machine for software development prepared with Vagrant that I want to start during boot on a Linux machine called jupiter as a normal user luis.

I connect as luis

luis @ idefix ➜  ~  ssh -Y -a luis@jupiter.tudominio.com
luis@jupiter:~$

I grant permission to luis (from root) to enable this lingering feature

luis@jupiter:~$ sudo loginctl enable-linger luis
luis@jupiter:~$

I prepare my file: ~/.config/systemd/user/devbox.service:

[Unit]
AssertPathExists=/home/luis/devbox

[Service]
WorkingDirectory=/home/luis/devbox
ExecStart=/usr/bin/vagrant up
Restart=always
PrivateTmp=true
NoNewPrivileges=true

[Install]
WantedBy=default.target

I enable, start, and check the devbox.service

luis@jupiter:~$ systemctl --user enable devbox.service
Created symlink /home/luis/.config/systemd/user/default.target.wants/devbox.service → /home/luis/.config/systemd/user/devbox.service.

luis@jupiter:~$ systemctl --user start devbox
luis@jupiter:~$ systemctl --user status devbox
● devbox.service
     Loaded: loaded (/home/luis/.config/systemd/user/devbox.service; enabled; vendor preset: enabled)
     Active: active (running) since Sun 2021-05-30 13:52:41 CEST; 37s ago
   Main PID: 4541 (vagrant)
      Tasks: 4 (limit: 18983)
     Memory: 71.2M
        CPU: 2.990s
     CGroup: /user.slice/user-1000.slice/user@1000.service/app.slice/devbox.service
             └─4541 /usr/bin/ruby /usr/bin/vagrant up

:

From now on, every time the system restarts, the systemd manager will execute the vagrant up command (as user luis) during boot.

| Note: In my case I received the error Failed to connect to bus: $DBUS_SESSION_BUS_ADDRESS and $XDG_RUNTIME_DIR not defined. I was connecting via ssh and the server had the option UsePAM no. I changed it to UsePAM yes, restarted the sshd server, and reconnected |

Configuration#

Configuration