useradd - create a new user or update default new user information
[SYNOPSIS] useradd OPTION USER
option
-s the login shell for the new user account
# useradd -s /sbin/nologin user
-d home directory for the new user account
# useradd -d /home/user user
-g force use GROUP for the new user account
# useradd -g group user
-e set account expiration date to EXPIRE_DATE
# useradd -e 20081231 user
-u force use the UID for the new user account
# useradd -u 550 user
-m create home directory for the new user account
# useradd -m user
-M do not create user's home directory(overrides /etc/login.defs)
# useradd -M user