useradd - create a new user or update default new user information
useradd [options] LOGIN
useradd -D useradd -D [options]
When invoked without the -D option, the useradd command creates a new user account using the values specified on the command line plus the default values from the system. Depending on command line options, the useradd command will update system files and may also create the new user's home directory and copy initial files.
By default, a group will also be created for the new user (see -g, -N, -U, and USERGROUPS_ENAB).
The options which apply to the useradd command are:
-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. The directory HOME_DIR does not have to exist but will not be created if it is missing. -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.