usermod
AccountsPackage: passwdHandle with care
Changes an existing account: its groups, its shell, its expiry, its lock. The options look alike and do not do the same thing — -G replaces the group list, -aG adds to it.
A mistake with this command can destroy data or lock you out
usermod -Gwithout-areplaces every secondary group of the account with the ones you list. On an admin account, that is how you losesudowhile trying to add yourself todocker.
What its options do in the lessons
From the same glossary the lessons render under their commands, so the two cannot disagree.
usermod -a- Appends to the listed groups instead of replacing the list. Only valid with
-G— forgetting it removes the user from every other group. usermod -G- The supplementary groups. On its own it *replaces* the list; with
-ait adds to it. usermod --lock- Locks the password by prefixing it with
!: no password login remains, without deleting the account or its files. usermod --expiredate- The date the account is disabled.
--expiredate 1disables it immediately. usermod --unlock- Removes the
!in front of the hash, so the previous password works again. If there is nothing behind the!, the command refuses rather than leave a passwordless account.