PWCK linux command manual

PWCK(1)                                                                PWCK(1)

       pwck - verify integrity of password files

       pwck [-sr] [passwd shadow]

       pwck  verifies the integrity of the system authentication information.
       All entries in the /etc/passwd and /etc/shadow are checked to see that
       the  entry  has  the  proper format and valid data in each field.  The
       user is prompted to delete entries that are  improperly  formatted  or
       which have other incorrectable errors.

       Checks are made to verify that each entry has

            - the correct number of fields
            - a unique user name
            - a valid user and group identifier
            - a valid primary group
            - a valid home directory
            - a valid login shell

       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.

       By  default,  pwck  operates on the files /etc/passwd and /etc/shadow.
       The user may select alternate files with the passwd and shadow parame-
       ters.   Additionally,  the  user  may execute the command in read-only
       mode by specifying the -r flag.  This causes all  questions  regarding
       changes  to  be  answered no without user intervention.  pwck can also
       sort entries in /etc/passwd and /etc/shadow by UID. To run it in  sort
       mode pass it -s flag. No checks are performed then, it just sorts.

       /etc/passwd - user account information
       /etc/shadow - encrypted password information
       /etc/group - group information

       group(5), passwd(5), shadow(5), usermod(8)

       The pwck command exits with the following values:

       0    Success

       1    Syntax Error

       2    One or more bad password entries

       3    Cannot open password files

       4    Cannot lock password files

       5    Cannot update password files

       Julianne Frances Haugh (