Backup for /etc/passwd , /etc/group , /etc/shadow

/etc/passwd /etc/group /etc/shadow are very essential file systems for Linux. You should not be surprised that linux does do a backup of the /etc/passwd /etc/group /etc/shadow. They are represented by

/etc/passwd-
/etc/group-
/etc/shadow-

So in case your any of your /etc/passwd /etc/group /etc/shadow are corrupted, just do a copy and replace