The options which apply to the useradd command are:
--badname
Allow names that do not conform to standards.
-b, --base-dir BASE_DIR
The default base directory for the system if -d HOME_DIR is
not specified. BASE_DIR is concatenated with the account
name to define the home directory. If the -m option is not
used, BASE_DIR must exist.
If this option is not specified, useradd will use the base
directory specified by the HOME variable in
/etc/default/useradd, or /home by default.
-c, --comment COMMENT
Any text string. It is generally a short description of the
login, and is currently used as the field for the user's full
name.
-d, --home-dir HOME_DIR
The new user will be created using HOME_DIR as the value for
the user's login directory. The default is to append the
LOGIN name to BASE_DIR and use that as the login directory
name. If the directory HOME_DIR does not exist, then it will
be created unless the -M option is specified.
-D, --defaults
See below, the subsection "Changing the default values".
-e, --expiredate EXPIRE_DATE
The date on which the user account will be disabled. The date
is specified in the format YYYY-MM-DD.
If not specified, useradd will use the default expiry date
specified by the EXPIRE variable in /etc/default/useradd, or
an empty string (no expiry) by default.
-f, --inactive INACTIVE
The number of days after a password expires until the account
is permanently disabled. A value of 0 disables the account as
soon as the password has expired, and a value of -1 disables
the feature.
If not specified, useradd will use the default inactivity
period specified by the INACTIVE variable in
/etc/default/useradd, or -1 by default.
-g, --gid GROUP
The group name or number of the user's initial login group.
The group name must exist. A group number must refer to an
already existing group.
If not specified, the behavior of useradd will depend on the
USERGROUPS_ENAB variable in /etc/login.defs. If this variable
is set to yes (or -U/--user-group is specified on the command
line), a group will be created for the user, with the same
name as her loginname. If the variable is set to no (or
-N/--no-user-group is specified on the command line), useradd
will set the primary group of the new user to the value
specified by the GROUP variable in /etc/default/useradd, or
100 by default.
-G, --groups GROUP1[,GROUP2,...[,GROUPN]]]
A list of supplementary groups which the user is also a
member of. Each group is separated from the next by a comma,
with no intervening whitespace. The groups are subject to the
same restrictions as the group given with the -g option. The
default is for the user to belong only to the initial group.
-h, --help
Display help message and exit.
-k, --skel SKEL_DIR
The skeleton directory, which contains files and directories
to be copied in the user's home directory, when the home
directory is created by useradd.
This option is only valid if the -m (or --create-home) option
is specified.
If this option is not set, the skeleton directory is defined
by the SKEL variable in /etc/default/useradd or, by default,
/etc/skel.
If possible, the ACLs and extended attributes are copied.
-K, --key KEY=VALUE
Overrides /etc/login.defs defaults (UID_MIN, UID_MAX, UMASK,
PASS_MAX_DAYS and others).
Example: -K PASS_MAX_DAYS=-1 can be used when creating system
account to turn off password aging, even though system
account has no password at all. Multiple -K options can be
specified, e.g.: -K UID_MIN=100 -K UID_MAX=499
-l, --no-log-init
Do not add the user to the lastlog and faillog databases.
By default, the user's entries in the lastlog and faillog
databases are reset to avoid reusing the entry from a
previously deleted user.
-m, --create-home
Create the user's home directory if it does not exist. The
files and directories contained in the skeleton directory
(which can be defined with the -k option) will be copied to
the home directory.
By default, if this option is not specified and CREATE_HOME
is not enabled, no home directories are created.
The directory where the user's home directory is created must
exist and have proper SELinux context and permissions.
Otherwise the user's home directory cannot be created or
accessed.
-M, --no-create-home
Do no create the user's home directory, even if the system
wide setting from /etc/login.defs (CREATE_HOME) is set to
yes.
-N, --no-user-group
Do not create a group with the same name as the user, but add
the user to the group specified by the -g option or by the
GROUP variable in /etc/default/useradd.
The default behavior (if the -g, -N, and -U options are not
specified) is defined by the USERGROUPS_ENAB variable in
/etc/login.defs.
-o, --non-unique
Allow the creation of a user account with a duplicate
(non-unique) UID.
This option is only valid in combination with the -u option.
-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 account.
System users will be created with no aging information in
/etc/shadow, and their numeric identifiers are chosen in the
SYS_UID_MIN-SYS_UID_MAX range, defined in /etc/login.defs,
instead of UID_MIN-UID_MAX (and their GID counterparts for
the creation of groups).
Note that useradd will not create a home directory for such a
user, regardless of the default setting in /etc/login.defs
(CREATE_HOME). You have to specify the -m options if you want
a home directory for a system account to be created.
-R, --root CHROOT_DIR
Apply changes in the CHROOT_DIR directory and use the
configuration files from the CHROOT_DIR directory.
-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.
-s, --shell SHELL
The name of the user's login shell. The default is to leave
this field blank, which causes the system to select the
default login shell specified by the SHELL variable in
/etc/default/useradd, or an empty string by default.
-u, --uid UID
The numerical value of the user'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 UID_MIN and greater than every other
user.
See also the -r option and the UID_MAX description.
-U, --user-group
Create a group with the same name as the user, and add the
user to this 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.
-Z, --selinux-user SEUSER
The SELinux user for the user's login. The default is to
leave this field blank, which causes the system to select the
default SELinux user.
Changing the default values
When invoked with only the -D option, useradd will display the
current default values. When invoked with -D plus other options,
useradd will update the default values for the specified options.
Valid default-changing options are:
-b, --base-dir BASE_DIR
The path prefix for a new user's home directory. The user's
name will be affixed to the end of BASE_DIR to form the new
user's home directory name, if the -d option is not used when
creating a new account.
This option sets the HOME variable in /etc/default/useradd.
-e, --expiredate EXPIRE_DATE
The date on which the user account is disabled.
This option sets the EXPIRE variable in /etc/default/useradd.
-f, --inactive INACTIVE
The number of days after a password has expired before the
account will be disabled.
This option sets the INACTIVE variable in
/etc/default/useradd.
-g, --gid GROUP
The group name or ID for a new user's initial group (when the
-N/--no-user-group is used or when the USERGROUPS_ENAB
variable is set to no in /etc/login.defs). The named group
must exist, and a numerical group ID must have an existing
entry.
This option sets the GROUP variable in /etc/default/useradd.
-s, --shell SHELL
The name of a new user's login shell.
This option sets the SHELL variable in /etc/default/useradd.
