User management
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The following commands are common commands for managing users on a Linux system, particularly in a multi-user or networked Linux environment.
| Command | Function |
|---|---|
| chage | Set or change password expiration (age) policy |
| chage -d 0 user | Make user password expire (requires user to change password on net logon) |
| chage -E YYYY-MM-DD user | Change password expiry |
| chage -E0 user | Disable account |
| chage -E1 user | Re-enable account |
| chage -M -W -I -d user | Set or change password expiration for user: -M maximum number of days between password changes; -W number of days for user to receive warning before expiration; -I inactive days after password expiration before account is locked; -d days since password was changed (setting to 0 forces password change on next logon) |
| chfn user | Change finger information for a user |
| finger | Display information about a user |
| grep user /etc/shadow | Check account status (! = locked account; !! = password locked) |
| groupadd group | Create a new group |
| groupdel group | Remove a group |
| groups | Shows which groups a user is in |
| id | Display UID and GID of the current user |
| last | Display the last users who have logged onto the system. |
| grep 'still logged in' | Find users who last logged in |
| lastlog | Lists login attempts and times for all users |
| lslogins | Display information on known users |
| passwd | Set or change password |
| passwd -l user | Lock password |
| passwd -u user | Unlock password |
| quota | List user’s quotas |
| quota | List user’s quotas |
| su user | Access superuser privileges |
| useradd -c "John Smith" -m john | Create an account named john, with a comment of "John Smith" and create the user's home directory. |
| useradd user | Add a new user account |
| userdel -r user | Delete a user account |
| usermod -aG group user | Add a user to a specific group |
| usermod -L user | Lock account |
| usermod option user | Change the user account information including, group, home directory, shell, expiration date |
| users | Find users who are logged in |
| visudo | Edit /etc/sudoers file |
| w | Display all users who are logged in to the machine and their active processes |
| who | Display all users who are logged in to the machine |
| whoami | Displays current user |
