pwck [-q] [-s] [passwd [ shadow ]]

       pwck [-q] [-r] [passwd [ shadow ]]

       The pwck command verifies the integrity of the users and authentication
       information. It checks that all entries in /etc/passwd and /etc/shadow
       have the proper format and contain valid data. The user is prompted to
       delete entries that are improperly formatted or which have other
       uncorrectable errors.

       Checks are made to verify that each entry has:

       o   the correct number of fields

       o   a unique and valid user name

       o   a valid user and group identifier

       o   a valid primary group

       o   a valid home directory

       o   a valid login shell

       shadow checks are enabled when a second file parameter is specified or
       when /etc/shadow exists on the system.

       These checks are the following:

       o   every passwd entry has a matching shadow entry, and every shadow
           entry has a matching passwd entry

       o   passwords are specified in the shadowed file

       o   shadow entries have the correct number of fields

       o   shadow entries are unique in shadow

       o   the last password changes are not in the future

       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.
           Sort entries in /etc/passwd and /etc/shadow by UID.

       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:

       PASS_MAX_DAYS (number)
           The maximum number of days a password may be used. If the password
           is older than this, a password change will be forced. If not
           specified, -1 will be assumed (which disables the restriction).

       PASS_MIN_DAYS (number)
           The minimum number of days allowed between password changes. Any
           password changes attempted sooner than this will be rejected. If
           not specified, -1 will be assumed (which disables the restriction).

       PASS_WARN_AGE (number)
           The number of days warning given before a password expires. A zero
           means warning is given only upon the day of expiration, a negative
           value means no warning is given. If not specified, no warning will
           be provided.

           Group account information.

           User account information.

           Secure user account information.

       The pwck command exits with the following values:


           invalid command syntax

           one or more bad password entries

           can't open password files

           can't lock password files

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