Managing Linux user accounts from the command line is a core sysadmin skill — the GUI tools most distros offer are fine for a desktop, but servers are managed via these commands almost exclusively.
# Create a new user with a home directory and specific shell sudo useradd -m -s /bin/bash alice # Set their password sudo passwd alice # Add an existing user to a group (e.g. sudo/wheel, or docker) sudo usermod -aG sudo alice # -a is critical - appends, doesn't replace existing groups # Lock an account without deleting it sudo usermod -L alice sudo passwd -l alice # equivalent # Delete a user, optionally removing their home directory too sudo userdel -r alice # List a user's group memberships groups alice id alice
The -a Flag Mistake
Forgetting -aG and using just -G instead REPLACES a user’s existing group memberships entirely rather than adding to them — a classic mistake that silently removes a user from groups they were supposed to keep, often not discovered until something they used to have access to suddenly breaks.