groupadd - create a new group
groupadd [OPTIONS] NEWGROUP
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.
Groupnames may contain only lower and upper case letters, digits, underscores, or dashes. They can end with a dollar sign. Dashes are not allowed at the beginning of the groupname. Fully numeric groupnames and groupnames . or .. are also disallowed.
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: \n, tabulation: \t, etc.).
On Ubuntu, the same constraints as Debian are in place, with the additional constraint that the groupname cannot be fully numeric. This includes octal and hexadecimal syntax.
Groupnames may only be up to 32 characters long.
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 groups ID.
GIDmust 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-KGID_MAX=499Note: -K
GID_MIN=10,GID_MAX=499doesnt work yet.
-o, --non-unique
permits the creation of a group with an already used numerical ID. As a result, for this
GID, the mapping towards groupNEWGROUPmay not be unique.
-p, --password
PASSWORD
defines an initial password for the group account. PASSWORD is expected to be encrypted, as returned by crypt (3).
Without this option, the group account will be locked and with no password defined, i.e. a single exclamation mark in the respective field of ths system account file /etc/group or /etc/gshadow.
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 systems 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_DIRdirectory and use the configuration files from theCHROOT_DIRdirectory. Only absolute paths are supported.
-P, --prefix
PREFIX_DIR
Apply changes to configuration files under the root filesystem found under the directory
PREFIX_DIR. 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 list of usernames to add as members of the group.
The default behavior (if the -g, -N, 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:
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).
/etc/group
Group account information.
/etc/gshadow
Secure group account information.
/etc/login.defs
Shadow password suite configuration.
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.
The groupadd command exits with the following values:
0
success
2
invalid command syntax
3
invalid argument to option
4
GID is already used (when called without -o)
9
group name is already used
10
cant update group file