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groupmod(8) [centos man page]

GROUPMOD(8)						    System Management Commands						       GROUPMOD(8)

NAME
groupmod - modify a group definition on the system SYNOPSIS
groupmod [options] GROUP DESCRIPTION
The groupmod command modifies the definition of the specified GROUP by modifying the appropriate entry in the group database. OPTIONS
The options which apply to the groupmod command are: -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. CONFIGURATION
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. FILES
/etc/group Group account information. /etc/gshadow Secure group account information. /etc/login.defs Shadow password suite configuration. /etc/passwd User account information. EXIT VALUES
The groupmod command exits with the following values: 0 success 2 invalid command syntax 3 invalid argument to option 4 specified group doesn't exist 6 specified group doesn't exist 9 group name already in use 10 can't update group file SEE ALSO
chfn(1), chsh(1), passwd(1), gpasswd(8), groupadd(8), groupdel(8), login.defs(5), useradd(8), userdel(8), usermod(8). shadow-utils 4.1.5.1 05/25/2012 GROUPMOD(8)

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GROUPADD(8)						    System Management Commands						       GROUPADD(8)

NAME
groupadd - create a new group SYNOPSIS
groupadd [options] group DESCRIPTION
The groupadd command creates a new group account using the values specified on the command line plus the default values from the system. The new group will be entered into the system files as needed. OPTIONS
The options which apply to the groupadd command are: -f, --force This option causes the command to simply exit with success status if the specified group already exists. When used with -g, and the specified GID already exists, another (unique) GID is chosen (i.e. -g is turned off). -g, --gid GID The numerical value of the group's ID. This value must be unique, unless the -o option is used. The value must be non-negative. The default is to use the smallest ID value greater than or equal to GID_MIN and greater than every other group. See also the -r option and the GID_MAX description. -h, --help Display help message and exit. -K, --key KEY=VALUE Overrides /etc/login.defs defaults (GID_MIN, GID_MAX and others). Multiple -K options can be specified. Example: -K GID_MIN=100 -K GID_MAX=499 Note: -K GID_MIN=10,GID_MAX=499 doesn't work yet. -o, --non-unique This option permits to add a group with a non-unique GID. -p, --password PASSWORD The encrypted password, as returned by crypt(3). The default is to disable the password. 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, --system Create a system group. The numeric identifiers of new system groups are chosen in the SYS_GID_MIN-SYS_GID_MAX range, defined in login.defs, instead of GID_MIN-GID_MAX. -R, --root CHROOT_DIR Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory. CONFIGURATION
The following configuration variables in /etc/login.defs change the behavior of this tool: GID_MAX (number), GID_MIN (number) Range of group IDs used for the creation of regular groups by useradd, groupadd, or newusers. The default value for GID_MIN (resp. GID_MAX) is 1000 (resp. 60000). 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. SYS_GID_MAX (number), SYS_GID_MIN (number) Range of group IDs used for the creation of system groups by useradd, groupadd, or newusers. The default value for SYS_GID_MIN (resp. SYS_GID_MAX) is 101 (resp. GID_MIN-1). FILES
/etc/group Group account information. /etc/gshadow Secure group account information. /etc/login.defs Shadow password suite configuration. CAVEATS
It is usually recommended to only use groupnames that begin with a lower case letter or an underscore, followed by lower case letters, digits, underscores, or dashes. They can end with a dollar sign. In regular expression terms: [a-z_][a-z0-9_-]*[$]? On Debian, the only constraints are that groupnames must neither start with a dash ('-') nor plus ('+') nor tilde ('~') nor contain a colon (':'), a comma (','), or a whitespace (space:' ', end of line: ' ', tabulation: ' ', etc.). Groupnames may only be up to 32 characters long. You may not add a NIS or LDAP group. This must be performed on the corresponding server. If the groupname already exists in an external group database such as NIS or LDAP, groupadd will deny the group creation request. EXIT VALUES
The groupadd command exits with the following values: 0 success 2 invalid command syntax 3 invalid argument to option 4 GID not unique (when -o not used) 9 group name not unique 10 can't update group file SEE ALSO
chfn(1), chsh(1), passwd(1), gpasswd(8), groupdel(8), groupmod(8), login.defs(5), useradd(8), userdel(8), usermod(8). shadow-utils 4.1.5.1 05/25/2012 GROUPADD(8)

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