Linux · User & Group Administration

PAM decides how to authenticate, but something else decides where user, group, and host names are looked up. What subsystem is that, which file configures it, and what does a line like passwd: files systemd sss mean?

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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?

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