userdel -r vivek
userdel: user vivek is currently used by process 749
How do I fix this problem and delete username vivek on a Debian Linux 9.x server?
One can use the userdel command to delete a user account on a Debian or any other Linux distro. It is a low level utility for removing users.
On Debian, sysadmin should usually use deluser command instead.
It seems that PID # 749 used by a user named vivek. It can be simple open ssh session or something running in the background. Use the ps command to find out about a PID # 749:
$ ps aux | grep 749
vivek 749 0.0 0.1 92716 4028 ? S 17:03 0:00 sshd: vivek@pts/0 root 10038 0.0 0.0 12784 944 pts/1 S+ 17:13 0:00 grep 749
The ‘sshd: vivek@pts/0’ indicates that active ssh session. From the man page:
userdel will not allow you to remove an account if there are running processes which belong to this account. In that case, you may have to kill those processes or lock the user’s password or account and remove the account later. The -f option can force the deletion of this account.
So, all you have to do is kill this PID and run the userdel command again using either the kill command/killall command:
# kill -15 749
# killall -TERM -u vivek
$ ps aux | grep 749
Now delete the user account name vivek:
# userdel -r vivek
Verify that user account deleted from /etc/passwd and /etc/shadow file with the id command or grep command:
$ id vivek
$ grep ^vivek /etc/passwd
$ grep vivek /etc/shadow
Another option is to pass the -f option to the userdel command. This option forces the removal of the user account, even if the user is still logged in. It also forces userdel to remove the user’s home directory and mail spool, even if another user uses the same home directory or if the mail spool is not owned by the specified user. You must be very careful while using the -f option as it may leave your system in an inconsistent state:
# userdel -f userNameHere
See man pages for more info:
$ man userdel
$ man deluser
$ man 5 passwd
$ man 5 shadow