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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CONFIGURATION | FILES | EXIT VALUES | SEE ALSO | COLOPHON |
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GRPCK(8) System Management Commands GRPCK(8)
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. 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.
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.
/etc/group
Group account information.
/etc/gshadow
Secure group account information.
/etc/passwd
User account information.
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
group(5), groupmod(8), gshadow(5), passwd(5), pwck(8), shadow(5).
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
⟨https://github.com/shadow-maint/shadow⟩. If you have a bug report
for this manual page, send it to
[email protected]. This page was obtained
from the project's upstream Git repository
⟨https://github.com/shadow-maint/shadow⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-10.) 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
[email protected]
shadow-utils 4.18.0 08/11/2025 GRPCK(8)
Pages that refer to this page: gpasswd(1), gshadow(5), pwck(8), pwconv(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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