How To Add a User
If you are signed in as the root user, you can create a new user at any time by typing:
adduser newuser
If you are signed in as a non-root user who has been given sudo privileges, as demonstrated in the initial server setup guide, you can add a new user by typing:
sudo adduser newuser
Either way, you will be asked a series of questions. The procedure will be:
• Assign and confirm a password for the new user
• Enter any additional information about the new user. This is entirely optional and can be skipped by hitting "ENTER" if you don't wish to utilize these fields.
• Finally, you'll be asked to confirm that the information you provided was correct. Type "Y" to continue.
Your new user is now ready for use! You can now log in using the password you set up.
Note: Continue on if you need your new user to have access to administrative functionality.
How To Grant a User Sudo Privileges
If your new user should have the ability to execute commands with root (administrative) privileges, you will need to give the new user access to sudo.
We can do this by using the visudo command, which opens the appropriate configuration file in your editor. This is the safest way to make these changes.
If you are currently signed in as the root user, type:
visudo
If you are signed i
n using a non-root user with sudo privileges, type:
sudo visudo
Search for the line that looks like this:
root ALL=(ALL:ALL) ALL
Below this line, copy the format you see here, changing only the word "root" to reference the new user that you would like to give sudo privileges to:
root ALL=(ALL:ALL) ALL
newuser ALL=(ALL:ALL) ALL
You should add a new line like this for each user that should be given full sudo privileges. When you are finished, you can save and close the file by hitting CTRL-X, followed by "Y", and then hit "ENTER" to confirm.
Now, your new user is able to execute commands with administrative privileges.
When signed in as the new user, you can execute commands as your regular user by typing commands as normal:
some_command
You can execute the same command with administrative privileges by typing sudo ahead of the command:
sudo some_command
You will be prompted to enter the password of the regular user account you are signed in as.
How To Delete a User
In the event that you no longer need a user, it is best to delete the old account.
You can delete the user itself, without deleting any of his or her files by typing this as root:
deluser newuser
If you are signed in as another non-root user with sudo privileges, you could instead type:
sudo deluser newuser
If, instead, you want to delete the user's home directory when the user is deleted, you can issue the following command as root:
deluser --remove-home newuser
If you're running this as a non-root user with sudo privileges, you would instead type:
sudo deluser --remove-home newuser
If you had previously configured sudo privileges for the user you deleted, you may want to remove the relevant line again by typing:
visudo
Or use this if you are a non-root user with sudo privileges:
sudo visudo
root ALL=(ALL:ALL) ALL
newuser ALL=(ALL:ALL) ALL # DELETE THIS LINE
This will prevent a new user created with the same name from being accidentally given sudo privileges.
This guide is from Jastin Ellingwood @ Digital Ocean. I am just trying to Decentralization this baby.