How to Create New User Account in Ubuntu Linux from command line?

Use useradd command create a new user or update default new user information from command line.

useradd testuser
passwd testuser

The above command will create a user named testuser and set its password to testuser. 

Some important files that define various properties etc for this user: 

• /etc/passwd - User account information.
• /etc/shadow - Secure user account information such as password.
• /etc/group - Group account information.
• /etc/default/useradd - Default values for account creation.
• /etc/skel/ - Directory containing default files.
• /etc/login.defs - Shadow password suite configuration.

Above command useradd will not create a home directory for this user. To create those try the below command that will create the user as well as home directory for it. 

sudo useradd -m -k /etc/skel -d /home/testuser testuser

This will create a user named test user with a home directory /home/testuser and will have the same files and settings as in /etc/skel.

To delete the user follow command: 

sudo userdel testuser