grpck(8) — Linux manual page


GRPCK(8)               System Management Commands               GRPCK(8)

NAME         top

       grpck - verify integrity of group files

SYNOPSIS         top

       grpck [options] [group [ shadow ]]

DESCRIPTION         top

       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.

OPTIONS         top

       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

       -R, --root CHROOT_DIR
           Apply changes in the CHROOT_DIR directory and use the
           configuration files from the CHROOT_DIR directory. Only
           absolute paths are supported.

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

       -S, --silence-warnings
           Suppress more controversial warnings, in particular warnings
           about inconsistency between group members listed in
           /etc/group and /etc/ghadow.

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


       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 group.

           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 characters.

           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.

FILES         top

           Group account information.

           Secure group account information.

           User account information.

EXIT VALUES         top

       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

SEE ALSO         top

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

COLOPHON         top

       This page is part of the shadow-utils (utilities for managing
       accounts and shadow password files) project.  Information about
       the project can be found at 
       ⟨⟩.  If you have a bug
       report for this manual page, send it to  This page was obtained
       from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-12-15.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

shadow-utils 4.11.1            12/22/2023                       GRPCK(8)

Pages that refer to this page: gpasswd(1)gshadow(5)pwck(8)pwconv(8)