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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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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CONFIGURATION | FILES | EXIT VALUES | SEE ALSO | COLOPHON |
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GROUPMOD(8) System Management Commands GROUPMOD(8)
groupmod - modify a group definition on the system
groupmod [options] GROUP
The groupmod command modifies the definition of the specified
GROUP by modifying the appropriate entry in the group database.
The options which apply to the groupmod command are:
-a, --append
If group members are specified with -U, append them to the
existing member list, rather than replacing it.
-g, --gid GID
The group ID of the given GROUP will be changed to GID.
The value of GID must be a non-negative decimal integer. This
value must be unique, unless the -o option is used.
Users who use the group as primary group will be updated to
keep the group as their primary group.
Any files that have the old group ID and must continue to
belong to GROUP, must have their group ID changed manually.
No checks will be performed with regard to the GID_MIN,
GID_MAX, SYS_GID_MIN, or SYS_GID_MAX from /etc/login.defs.
-h, --help
Display help message and exit.
-n, --new-name NEW_GROUP
The name of the group will be changed from GROUP to NEW_GROUP
name.
-o, --non-unique
When used with the -g option, allow to change the group GID to
a non-unique value.
-p, --password PASSWORD
The encrypted password, as returned by crypt(3).
Note: This option is not recommended because the password (or
encrypted password) will be visible by users listing the
processes.
You should make sure the password respects the system's
password policy.
-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.
-P, --prefix PREFIX_DIR
Apply changes in the PREFIX_DIR directory and use the
configuration files from the PREFIX_DIR directory. This option
does not chroot and is intended for preparing a
cross-compilation target. Some limitations: NIS and LDAP
users/groups are not verified. PAM authentication is using the
host files. No SELINUX support.
-U, --users
A comma-separated list of usernames to add as members of the
group.
The default behavior (if the -g and -U options are not
specified) is defined by the USERGROUPS_ENAB variable in
/etc/login.defs.
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/login.defs
Shadow password suite configuration.
/etc/passwd
User account information.
The groupmod command exits with the following values:
0
E_SUCCESS: success
2
E_USAGE: invalid command syntax
3
E_BAD_ARG: invalid argument to option
4
E_GID_IN_USE: group id already in use
6
E_NOTFOUND: specified group doesn't exist
9
E_NAME_IN_USE: group name already in use
10
E_GRP_UPDATE: can't update group file
11
E_CLEANUP_SERVICE: can't setup cleanup service
12
E_PAM_USERNAME: can't determine your username for use with pam
13
E_PAM_ERROR: pam returned an error, see syslog facility id
groupmod for the PAM error message
chfn(1), chsh(1), passwd(1), gpasswd(8), groupadd(8), groupdel(8),
login.defs(5), useradd(8), userdel(8), usermod(8).
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 GROUPMOD(8)
Pages that refer to this page: gpasswd(1), groupadd(8), groupdel(8), grpck(8), useradd(8), userdel(8), usermod(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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