Modifying a User
Important Considerations
- Some changes (e.g., login name) cannot be applied if the user is logged in.
- Group membership changes take effect after the user logs out and logs back in.
-
Use
who,w, andlastto check who is currently logged in: -
who– Shows currently logged-in users. w– Verbose; shows logged-in users, system uptime, load, and running processes.last– Shows past login sessions; can filter by username or tty.
usermod Command Options
| Option | Description | Example Command |
|---|---|---|
-c COMMENT |
Set GECOS/comment field. | usermod -c "Alamgir Here" alamgir |
-d HOME_DIR |
Set new home directory. | usermod -d /home/alamgir_new alamgir |
-e EXPIRE_DATE |
Set account expiration date. | usermod -e 2026-12-31 alamgir |
-f INACTIVE |
Permit login for INACTIVE days after password expires. | usermod -f 10 alamgir |
-g GROUP |
Set primary group. | usermod -g users alamgir |
-G GROUPS |
Set supplementary groups (overwrites existing unless -a is used). |
usermod -G cse,ict alamgir |
-a -G GROUPS |
Append supplementary groups instead of overwriting. | usermod -aG cps alamgir |
-h |
Show help. | usermod -h |
-l NEW_LOGIN |
Change login name. | usermod -l alamgirhere alamgir |
-L |
Lock the user account. | usermod -L alamgir |
-s SHELL |
Set login shell. | usermod -s /bin/bash alamgir |
-u NEW_UID |
Change user UID (may orphan files). | usermod -u 1500 alamgir |
-U |
Unlock the user account. | usermod -U alamgir |