How to rename a user safely?

Question

I've misspelled user name when installing Ubuntu and would like to rename if possible. How can I safely change my user name?

Answer 1

Safely? Don't rename at all. Instead, (make sure the user is logged out first) create a new user with the correct username, rename the old home directory to the new username and chown -R the folder to the new user.

This assumes that you're not using encrypted homes. That would require some different steps, but since I haven't done that myself, I'll leave that to someone else.

Answer 2

Use usermod like so:

usermod -l newname currentname

Answer 3

I have recently faces such problem and got working solution.

1. Make backup of the users- and groups-related files

   sudo cp /etc/passwd ~/passwd.bak
   sudo cp /etc/group ~/group.bak
   sudo cp /etc/subuid ~/subuid.bak
   sudo cp /etc/subgid ~/subgid.bak
   sudo cp /etc/gshadow ~/gshadow.bak
   sudo cp /etc/shadow ~/shadow.bak
   

2. We need to boot in Recovery mode (click Shift on boot, in GRUB select Advanced options for Ubuntu, select Ubuntu, with Linux ... (recovery mode))

3. Select root Drop to root shell prompt to access root-shell

4. Enter your main user (usually GID = 1000, member of sudo group) password here when asked

   Press Enter for maintenance
   (or press Control-D to continue):
   

5. Remount all filesystems with read and write

   mount -o rw,remount /
   mount -o rw,remount /home
   

6. Rename user from old_user to new_user, rename comment on user-name (field 5 in /etc/passwd) and move its home

   OLDNAME="old_user"
   NEWNAME="new_user"
   usermod -l $NEWNAME $OLDNAME -c $NEWNAME -d /home/$NEWNAME  -m
   

7. Rename user's group from old_user to new_user

   groupmod $OLDNAME -n $NEWNAME
   

8. Replace old_user to new_user in /etc/subgid and /etc/subuid

   sed -i "s/$OLDNAME/$NEWNAME/g" /etc/subuid
   sed -i "s/$OLDNAME/$NEWNAME/g" /etc/subgid
   

9. Reboot the system and then login with new_user name and old password. Optionally change password with passwd

10. If goes right - remove backed-up files:

    sudo rm ~/passwd.bak ~/group.bak ~/subuid.bak ~/subgid.bak \
    ~/gshadow.bak ~/shadow.bak
    

Note: you can read about used options of usermod and groupmod on their man-pages.