useradd

Create new user accounts or update default account information.
Unless invoked with the -D option, user must be given. useradd will create new entries in system files. Home directories and initial files may also be created as needed.

SYNTAX
      useradd [options] [user]

OPTIONS
  -c comment    Comment field.

  -d dir        Home directory.
                The default is to use user as the directory name
                under the home directory specified with the -D option.

  -e date       Account expiration date.
                date is in the format MM/DD/YYYY.
                Two-digit year fields are also accepted.
                The value is stored as the number of days since January 1, 1970.
                This option requires the use of shadow passwords.

  -f days       Permanently disable account this many days after the
                password has expired. A value of -1 disables this feature.
                This option requires the use of shadow passwords.

  -g group      Initial group name or ID number.
                If a different default group has not been specified using the -D option,
                the default group is 1.
  -G groups     Supplementary groups given by name or number in a comma-separated
                list with no whitespace.

  -k [dir]      Copy default files to user's home directory.
                Meaningful only when used with the -m option.
                Default files are copied from /etc/skel/ unless an alternate dir is specified.

  -m            Make user's home directory if it does not exist.
                The default is not to make the home directory.

  -o            Override. Accept a nonunique uid with the -u option. (Probably a bad idea.)

  -s shell      Login shell.

  -u uid        Numerical user ID. The value must be unique unless the -o option is used.
                The default value is the smallest ID value greater than 99 and greater
                than every other uid.

  -D [options]  Set or display defaults. If options are specified, set them.
                If no options are specified, display current defaults. The options are:

                  -b dir        Home directory prefix to be used in creating home directories.
                                If the -d option is not used when creating an account, the
                                user name will be appended to dir.

                 -e date        Expire date. Requires the use of shadow passwords.

                 -f days        Number of days after a password expires to disable an account.
                                Requires the use of shadow passwords.

                 -g group       Initial group name or ID number.

                 -s shell       Default login shell.

Related commands:

userdel [-r] user - Remove user and (optionally) the user's home directory
usermod - modify user account