As users are added, updated, and deleted it's quite easy for the administrative files to get out of sync with each other—especially if any manual file edits have been performed. Therefore, in this last section we'll look at a few of the utilities that can be used to check and maintain the related files (/etc/passwd, /etc/shadow, and /etc/group).
We've already come across pwconv—it was used in our custom script earlier. It is used to create or update the shadow file, which it does by synchronizing it with the password file.
It uses the second field of /etc/passwd (the encrypted password field) to indicate that the password for this user can be found in /etc/shadow. It does this by moving the encrypted password into