UNIX / Linux : How to delete root equivalent user (Non-Root User with UID 0)

If you try to delete a user with UID 0 by userdel command, you will get following error.

# id 
uid=0(root) gid=0(root) groups=0(root)
# userdel 
userdel: user user01 is currently used by process 1

All the processes are owned by user IDs and not user-names. So, All process owned by root will be owned by root equivalent user, as they have same UID. To work around this issue follow the steps given below.

Deleting non-root user with UID 0

If you need to delete non-root user having UID 0 (say user01), follow the steps below.

1. Backup the /etc/passwd file.

# cp /etc/passwd /etc/passwd_bkp

2. Open /etc/passwd and change the UID of user01 from 0 to to a UID which is not used by any other user, for example:
change below entry from

user01:x:0:0::/home/user01:/bin/bash

to an entry shown below:

user01:x:2000:0::/home/user01:/bin/bash

3. Now, delete the user with userdel command. This time you should not get any error.

# userdel user01