Checks are made to verify that each entry has:
shadow checks are enabled when a second file parameter is specified or when /etc/shadow exists on the system.
These checks are the following:
The checks for correct number of fields and unique user name are fatal. If the entry has the wrong number of fields, the user will be prompted to delete the entire line. If the user does not answer affirmatively, all further checks are bypassed. An entry with a duplicated user name is prompted for deletion, but the remaining checks will still be made. All other errors are warning and the user is encouraged to run the usermod command to correct the error.
The commands which operate on the /etc/passwd file are not able to alter corrupted or duplicated entries. pwck should be used in those circumstances to remove the offending entry.
The -r and -s options cannot be combined.
The options which apply to the pwck command are:
-R, --root CHROOT_DIR
By default, pwck operates on the files /etc/passwd and /etc/shadow. The user may select alternate files with the passwd and shadow parameters.
The following configuration variables in /etc/login.defs change the behavior of this tool:
The pwck command exits with the following values:
group(5), grpck(8), passwd(5), shadow(5), usermod(8).