shadow/man/man8/groupmod.8

'\" t
.\"     Title: groupmod
.\"    Author: Julianne Frances Haugh
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 03/19/2025
.\"    Manual: System Management Commands
.\"    Source: shadow-utils 4.17.4
.\"  Language: English
.\"
.TH "GROUPMOD" "8" "03/19/2025" "shadow\-utils 4\&.17\&.4" "System Management Commands"
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.SH "NAME"
groupmod \- modify a group definition on the system
.SH "SYNOPSIS"
.HP \w'\fBgroupmod\fR\ 'u
\fBgroupmod\fR [\fIoptions\fR] \fIGROUP\fR
.SH "DESCRIPTION"
.PP
The
\fBgroupmod\fR
command modifies the definition of the specified
\fIGROUP\fR
by modifying the appropriate entry in the group database\&.
.SH "OPTIONS"
.PP
The options which apply to the
\fBgroupmod\fR
command are:
.PP
\fB\-a\fR, \fB\-\-append\fR
.RS 4
If group members are specified with \-U, append them to the existing member list, rather than replacing it\&.
.RE
.PP
\fB\-g\fR, \fB\-\-gid\fR\ \&\fIGID\fR
.RS 4
The group ID of the given
\fIGROUP\fR
will be changed to
\fIGID\fR\&.
.sp
The value of
\fIGID\fR
must be a non\-negative decimal integer\&. This value must be unique, unless the
\fB\-o\fR
option is used\&.
.sp
Users who use the group as primary group will be updated to keep the group as their primary group\&.
.sp
Any files that have the old group ID and must continue to belong to
\fIGROUP\fR, must have their group ID changed manually\&.
.sp
No checks will be performed with regard to the
\fBGID_MIN\fR,
\fBGID_MAX\fR,
\fBSYS_GID_MIN\fR, or
\fBSYS_GID_MAX\fR
from
/etc/login\&.defs\&.
.RE
.PP
\fB\-h\fR, \fB\-\-help\fR
.RS 4
Display help message and exit\&.
.RE
.PP
\fB\-n\fR, \fB\-\-new\-name\fR\ \&\fINEW_GROUP\fR
.RS 4
The name of the group will be changed from
\fIGROUP\fR
to
\fINEW_GROUP\fR
name\&.
.RE
.PP
\fB\-o\fR, \fB\-\-non\-unique\fR
.RS 4
When used with the
\fB\-g\fR
option, allow to change the group
\fIGID\fR
to a non\-unique value\&.
.RE
.PP
\fB\-p\fR, \fB\-\-password\fR\ \&\fIPASSWORD\fR
.RS 4
The encrypted password, as returned by
\fBcrypt\fR(3)\&.
.sp
\fBNote:\fR
This option is not recommended because the password (or encrypted password) will be visible by users listing the processes\&.
.sp
You should make sure the password respects the system\*(Aqs password policy\&.
.RE
.PP
\fB\-R\fR, \fB\-\-root\fR\ \&\fICHROOT_DIR\fR
.RS 4
Apply changes in the
\fICHROOT_DIR\fR
directory and use the configuration files from the
\fICHROOT_DIR\fR
directory\&. Only absolute paths are supported\&.
.RE
.PP
\fB\-P\fR, \fB\-\-prefix\fR\ \&\fIPREFIX_DIR\fR
.RS 4
Apply changes in the
\fIPREFIX_DIR\fR
directory and use the configuration files from the
\fIPREFIX_DIR\fR
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\&.
.RE
.PP
\fB\-U\fR, \fB\-\-users\fR
.RS 4
A comma\-separated list of usernames to add as members of the group\&.
.sp
The default behavior (if the
\fB\-g\fR
and
\fB\-U\fR
options are not specified) is defined by the
\fBUSERGROUPS_ENAB\fR
variable in
/etc/login\&.defs\&.
.RE
.SH "CONFIGURATION"
.PP
The following configuration variables in
/etc/login\&.defs
change the behavior of this tool:
.PP
\fBMAX_MEMBERS_PER_GROUP\fR (number)
.RS 4
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)\&.
.sp
The default value is 0, meaning that there are no limits in the number of members in a group\&.
.sp
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\&.
.sp
If you need to enforce such limit, you can use 25\&.
.sp
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\&.
.RE
.SH "FILES"
.PP
/etc/group
.RS 4
Group account information\&.
.RE
.PP
/etc/gshadow
.RS 4
Secure group account information\&.
.RE
.PP
/etc/login\&.defs
.RS 4
Shadow password suite configuration\&.
.RE
.PP
/etc/passwd
.RS 4
User account information\&.
.RE
.SH "EXIT VALUES"
.PP
The
\fBgroupmod\fR
command exits with the following values:
.PP
\fI0\fR
.RS 4
E_SUCCESS: success
.RE
.PP
\fI2\fR
.RS 4
E_USAGE: invalid command syntax
.RE
.PP
\fI3\fR
.RS 4
E_BAD_ARG: invalid argument to option
.RE
.PP
\fI4\fR
.RS 4
E_GID_IN_USE: group id already in use
.RE
.PP
\fI6\fR
.RS 4
E_NOTFOUND: specified group doesn\*(Aqt exist
.RE
.PP
\fI9\fR
.RS 4
E_NAME_IN_USE: group name already in use
.RE
.PP
\fI10\fR
.RS 4
E_GRP_UPDATE: can\*(Aqt update group file
.RE
.PP
\fI11\fR
.RS 4
E_CLEANUP_SERVICE: can\*(Aqt setup cleanup service
.RE
.PP
\fI12\fR
.RS 4
E_PAM_USERNAME: can\*(Aqt determine your username for use with pam
.RE
.PP
\fI13\fR
.RS 4
E_PAM_ERROR: pam returned an error, see syslog facility id groupmod for the PAM error message
.RE
.SH "SEE ALSO"
.PP
\fBchfn\fR(1),
\fBchsh\fR(1),
\fBpasswd\fR(1),
\fBgpasswd\fR(8),
\fBgroupadd\fR(8),
\fBgroupdel\fR(8),
\fBlogin.defs\fR(5),
\fBuseradd\fR(8),
\fBuserdel\fR(8),
\fBusermod\fR(8)\&.