grpck
(8)verify integrity of group files
Options
5-h--helpDisplay help message and exit.
-r--read-onlyExecute the grpck command in read-only mode. This causes all questions regarding changes to be answered no without user intervention.
-R--rootCHROOT_DIRApply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory. Only absolute paths are supported.
-s--sortSort entries in /etc/group and /etc/gshadow by GID.
-S--silence-warningsSuppress more controversial warnings, in particular warnings about inconsistency between group members listed in /etc/group and /etc/ghadow.
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 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.
CONFIGURATION
The following configuration variables in /etc/login.defs change the behavior of this tool:
MAX_MEMBERS_PER_GROUP (number)
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.