Ubuntu Server is like any Linux range, and has full multi-user capacity, and a common task on any server is adding users.

useradd
using useradd command will you can easily add new :
useradd <username>
But without using any other options your user will not have a password or a home directory.

Using -d option you can set the home directory for the user. The -m option will force useradd to make the home directory. We will try creating a user account using this option, and after that use the passwd command to set the password. You can alternatively set a password using -p on the useradd command, but I choose to set the password using passwd command.
sudo useradd -d /home/testuser -m testuser

sudo passwd testuser
This will make the user named testuser and offer them their individual home directory in /home/testuser. The files in the new home directory are copied from the /etc/skel folder. If we a look at the new home directory for the user:
geek@ubuntuServ:/etc/skel$ ls -la /home/testuser
total 20

drwxr-xr-x 2 testuser testuser 4096 2006-12-15 11:34 .
drwxr-xr-x 5 root root 4096 2006-12-15 11:37 ..
-rw-r–r– 1 testuser testuser 220 2006-12-15 11:34 .bash_logout
-rw-r–r– 1 testuser testuser 414 2006-12-15 11:34 .bash_profile
-rw-r–r– 1 testuser testuser 2227 2006-12-15 11:34 .bashrc

You will observe that there are bash scripts in this directory. If you wanted to set default path options for all new users, you can modify the files in/etc/skel, which would then be used to make these files by the useradd command.
adduser

The adduser command very simple compare to useradd command, because it prompts you for every part of info. Here’s the syntax:
adduser <username>

Example:
geek@ubuntuServ:/etc/skel$ sudo adduser thegeek
Password:
Adding user `thegeek’…
Adding new group `thegeek’ (1004).
Adding new user `thegeek’ (1004) with group `thegeek’.
Creating home directory `/home/thegeek’.
Copying files from `/etc/skel’
Enter new UNIX password:
Retype new UNIX password:
No password supplied
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
Changing the user information for thegeek
Enter the new value, or press ENTER for the default
Full Name []: The Geek
Room Number []: 0
Work Phone []: 555-1212
Home Phone []: 555-1212
Other []:
Is the information correct? [y/N]