Provided by: passwd_4.8.1-2ubuntu2.2_amd64 bug


       grpck - verify integrity of group files


       grpck [options] [group [ shadow ]]


       The grpck command verifies the integrity of the groups information. It checks that all
       entries in /etc/group and /etc/gshadow 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:

       •   the correct number of fields

       •   a unique and valid group name

       •   a valid group identifier (/etc/group only)

       •   a valid list of members and administrators

       •   a corresponding entry in the /etc/gshadow file (respectively /etc/group for the
           gshadow checks)

       The checks for correct number of fields and unique group name are fatal. If an 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 group name is prompted for deletion, but the remaining checks will still be
       made. All other errors are warnings and the user is encouraged to run the groupmod command
       to correct the error.

       The commands which operate on the /etc/group and /etc/gshadow files are not able to alter
       corrupted or duplicated entries.  grpck should be used in those circumstances to remove
       the offending entries.


       The -r and -s options cannot be combined.

       The options which apply to the grpck command are:

       -h, --help
           Display help message and exit.

       -r, --read-only
           Execute the grpck command in read-only mode. This causes all questions regarding
           changes to be answered no without user intervention.

       -R, --root CHROOT_DIR
           Apply changes in the CHROOT_DIR directory and use the configuration files from the
           CHROOT_DIR directory.

       -s, --sort
           Sort entries in /etc/group and /etc/gshadow by GID.

       By default, grpck operates on /etc/group and /etc/gshadow. The user may select alternate
       files with the group and shadow parameters.


       The following configuration variables in /etc/login.defs change the behavior of this tool:

       MAX_MEMBERS_PER_GROUP (number)
           Maximum members per group entry. When the maximum is reached, a new group entry (line)
           is started in /etc/group (with the same name, same password, and same GID).

           The default value is 0, meaning that there are no limits in the number of members in a

           This feature (split group) permits to limit the length of lines in the group file.
           This is useful to make sure that lines for NIS groups are not larger than 1024

           If you need to enforce such limit, you can use 25.

           Note: split groups may not be supported by all tools (even in the Shadow toolsuite).
           You should not use this variable unless you really need it.


           Group account information.

           Secure group account information.

           User account information.


       The grpck command exits with the following values:


           invalid command syntax

           one or more bad group entries

           can't open group files

           can't lock group files

           can't update group files


       group(5), groupmod(8), gshadow(5), passwd(5), pwck(8), shadow(5).