useradd
Use the command useradd process (without any parameters)
useradd -D can modify the default configuration values for the new user's / etc / default / useradd
usermod modify user information, and usage almost useradd
Try not to use in practical work userdel to delete a user, instead of using the method of user comments in / etc / passwd, the systems and services to prevent users accidentally deleted bring abnormal
passwd can change the user's password and password expiration time, ordinary users can only change their own user password
