GRPCK - Online Linux Manual PageSection : 8
Updated : 03/06/2023
Source : shadow−utils 4​.13
Note : System Management Commands

NAMEgrpck − verify integrity of group files

SYNOPSISgrpck [options] [group [ shadow ]]

DESCRIPTIONThe 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​.

OPTIONSThe −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​.

CONFIGURATIONThe 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 VALUESThe 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 ALSOgroup(5), groupmod(8), gshadow(5), passwd(5), pwck(8), shadow(5)​.
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