pwck /etc/passwd Configuration Validator Linux Utility

I ran into the following error when trying to change my password:

passwd: Authentication token manipulation error
passwd: password unchanged

I found the following pwck linux command which validates the /etc/passwd and /etc/shadow config files, and advises of any problems.

From the man page:

       pwck - verify integrity of password files
       pwck [-q] [-s] [passwd shadow]
       pwck [-r] [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 uncorrectable 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.

Link to the askubunu thread where I found out about the pwck command:


 Linux utilities