Adding users in Linux

Add Users

#Create public and private key
#private and public key will be generated
$ ssh-keygen -f name

#Create user
$sudo adduser username --disabled-password

# Change to the new user
sudo su - username

#create a directory
$ mkdir .ssh

#change the permissions
$ chmod 700 .ssh

#Create a new file
$ touch .ssh/authorized_keys

#change the permissions
$ chmod 600 .ssh/authorized_keys

Important
Without these exact file permissions, the user will not be able to log in.
Open the authorized_keys file using your favorite text editor (such as vim or nano).

#copy the public key contents and paste it in the file
$ vim .ssh/authorized_keys

You need to modify the sudo settings to enable password authentication when using sudo. Run the visudo command as root (or sudo visudo) and look for a line like this:

ec2-user        ALL=(ALL)       NOPASSWD: ALL
Remove the NOPASSWD: bit, so the line looks like this:

ec2-user        ALL=(ALL)       ALL
sudo will ask for a password next time you log on. Again, make sure to set your password before doing this!

#link:https://brianflove.com/2013/06/18/add-new-sudo-user-to-ec2-ubuntu/