systemd is a not so new Linux init system. It's default on Debian systems. This is the very first process to start when Linux boots - it's PID is 1:
$ ps aux USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1 0.0 0.1 139092 6876 ? Ss 14:03 0:01 /sbin/init $ file /sbin/init /sbin/init: symbolic link to /lib/systemd/systemd
I've been running systemd for a while. But thanks to it's System V init script compatibility I've never actually written any scripts for it.
I wanted to start a simple bash script after linux booted and I decided it's time to use systemd to take care of business.
Unit files describe the services systemd manages. Very simple unit file that starts a bash script could be:
[Unit] Description=Starts some bash script [Service] WorkingDirectory=/home/povilas/ Type=forking ExecStart=/bin/bash my_script.sh KillMode=process [Install] WantedBy=multi-user.target
WantedBy option in the Install section means that this unit is wanted by multi-user.target unit. Meaning this unit becomes a dependency of multi-user.target unit.
Install unit file
Save the unit file to /etc/systemd/system/my_unit.service and enable it with:
# systemctl enable my_unit.service
Next time the OS boots, bash script will be executed.