Linux · User & Group Administration

A user's primary group and their supplementary groups are recorded in two different places. Where does each live, and what are the four fields of an /etc/group line?

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 User & Group Administration

Ubuntu tells you never to log in as root and instead run admin tasks through your own account with sudo. What is the actual state of the root account on such a system, and why does that make it a non-issue to leave root passwordless?

During a standard Debian install you can just press Next past the root password screen, leaving it blank. What does Debian silently do to the first user account as a result?

You have shell access on a fresh Debian box and need to run admin commands. How you enter admin mode depends on one earlier install choice — what determines whether you use sudo -s versus su -l?

The openSUSE installer sets up your new user and then, unusually, applies that same password to root unless you catch an easy-to-miss option. What justification is given, and why is it a security weak spot?

Linux usernames look like they could be anything, but there are real constraints. What are the rules for a login name, and what specifically can break if you use accented or non-ASCII characters in a password?

Debian gives you both adduser and useradd, and so does Fedora — but a script that works on Debian's adduser can misbehave on Fedora. Why?

Start learning today

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