Product Reviews

Linux 101: What are the Linux systemd equivalents of runlevels?

If systemd is a bit confusing to you, Jack Wallen is here to help ease that a bit by comparing systemd targets to sysvinit runlevels.

Image: Jack Wallen

If you’re a Linux admin, you probably remember the old runlevels, which defined a state of initialization the operating system is running in. For example, runlevel 0 was a system halt, runlevel 1 was single-user mode, runlevel 2 was multi-user mode with no network file system, run level 3 was multi-user mode with a text-only interface, run level 4 was user-definable, runlevel 5 was multi-user mode with a GUI and runlevel 6 was reboot. 

That was with sysvinit. Now that most Linux distributions have migrated to systemd, you might be curious as to the equivalent run levels. There isn’t a per-level equivalent, because opts to go with target levels, instead of run levels. Because there are only five targets, it doesn’t quite map out perfectly. 

SEE: Kubernetes: A cheat sheet (free PDF) (TechRepublic)

However, systemd takes a much more logical approach to runlevels. Here’s how systemd targets track with the old-school runlevels. poweroff.target is shutdown or power off, so it’s akin to runlevel 0. rescue.target launches the rescue shell session, so it’s like runlevel 1. multi-user.target launches the system in non-GUI, multi-user mode, so it’s like run levels 2, 3, and 4. graphical.target launches the system into a GUI, multi-user mode, so it’s like runlevel 5. 

Finally, reboot.target shuts down or reboots the system, so it’s like runlevel 6. Most of your systems will use runlevels 3, 4 or 5, which translates to either multi-user.target or graphical.target. 

These targets are defined in the systemd startup scripts in /etc/systemd/system and are generally found in the install section, as in WantedBy=multi-user.target. 

And those are the systemd equivalents of sysvinit runlevels. Hopefully, this helps to demystify systemd just a bit for you.

Subscribe to TechRepublic’s How To Make Tech Work on YouTube for all the latest tech advice for business pros from Jack Wallen.

Also see

 Source link

Back to top button
SoundCloud To Mp3