Error while adding user or modifying user 'cannot lock /etc/passwd; try again later'

Issue

• useradd: /etc/passwd.251778: Operation not permitted

• useradd: cannot lock /etc/passwd; try again later.

• Receiving error while adding or modifying the user

cannot lock /etc/passwd; try again later

• Unable to delete users using userdel command.

[root@example ~]# userdel test
userdel: unable to lock password file

• While manually editing the /etc/passwd file gives following error:

"/etc/passwd" E212: Can't open file for writing

• useradd and passwd command is working fine but can't remove users with userdel and chage command.