Manual: grpck

GRPCK(8)					 System Management Commands					    GRPCK(8)

NAME
       grpck - verify integrity of group files

SYNOPSIS

       grpck [options] [group [ shadow ]]

DESCRIPTION
       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
       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. 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 parameters.

CONFIGURATION
       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
       /etc/group
	   Group account information.

       /etc/gshadow
	   Secure group account information.

       /etc/passwd
	   User account information.

EXIT VALUES
       The grpck command exits with the following values:

       0
	   success

       1
	   invalid command syntax

       2
	   one or more bad group entries

       3
	   can't open group files

       4
	   can't lock group files

       5
	   can't update group files

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

shadow-utils 4.17.4					 02/02/2026						    GRPCK(8)