Linux · systemd

In an Init-V runlevel directory like /etc/rc2.d you see files named S15sshd and K80sshd. What do the S, the K, and the number mean?

Answer locked. Get the free KnowCard app to reveal it — plus spaced-repetition review so it actually sticks.

This is one card from the KnowCard library — thousands more across SAP, Linux, Python and more. In the app you get the answer, AI explanations, and cards that come back right before you would forget them. Free to start on iOS, Android or the web.

More in systemd

In systemd terms, what is a target, and how do you find out (or change) which one the machine boots into by default?

After a fresh boot the kernel has loaded, but nothing else is running yet. What is the very first userspace process the kernel launches, and what is it responsible for?

Traditional init systems were collections of shell scripts. What is architecturally different about systemd, and how does it know when a service has crashed?

You run pstree and see one process at the root of the entire tree. Which PID is systemd, and why does /sbin/init sometimes appear to be process 1 instead?

What is the single central command for administering systemd services by hand, and what are its everyday subcommands?

A tutorial written for Fedora says to run systemctl start sshd, but on your Debian box the SSH unit isn't found under that name. What went wrong, and how far does this problem generalize?

Start learning today

Free to start — download the app or use it in your browser.