Types of systemd unit files

Unit files are stored in /usr/lib/systemd/system and /etc/systemd/system. There are several types of them:

• Service - this is the unit file that you would activate to manage the service
• Mount - to replace mounts that are coming trough /etc/fstab
• Timer - which is are replacement for starting jobs through cron at specific time
• Automount - which is closely tied together with the Mount unit type to automatically mount directories when they are needed
• Target - a very specific unit type. A Target is basically a group of unit files, but a Target can also be used as an endpoint. Examples: multiuser.target and graphical.target - defines the state that your machine should be booting in
• Path - which is a unit which is monitoring activity in some directory
• Device - a device file recognized by the kernel
• Scope - an externally created process
• Slice - a group of hierarchically organized units that manage system processes
• Snapshot - a saved state of the systemd manager
• Socket - an inter-process communication socket
• Swap - a swap device or a swap file