Automatic Login
This will automatically login into a certain user after reboot ... But, password will be required after screen lock or logout ... This is described in the official Ubuntu documentation:
Open the Activities overview and start typing Users.
Click Users to open the panel.
Press Unlock in the top right corner and type in your password when prompted.
If it is a different user account that you want to log into automatically, select the account under Other Users.
Switch the Automatic Login switch to on.
⚠ Passwordless Login ⚠
This will allow a user to login without a password e.g. by clicking on the username from the list of users in the login screen ... This is described in man passwd:
-d, --delete Delete a user's password (make it empty). This is a quick
way to disable a password for an account. It will set the named account
passwordless.
This means you need to, first, set a password for a certain user ... Then, delete it afterwords like so:
sudo passwd -d user
Where user is the actual username for the user you want to delete its password.
This, however, can be very dangerous(i.e. totally compromise your system, data and privacy) if that user is an administrator account ... Please, don't misinterpret my previous statement, it's still dangerous even for a normal(non administrator) account although to a much lesser extent.
Please, notice as well that this method doesn't make sense and cannot work normally if that user has an encrypted home directory which needs a password/passphrase to decrypt and mount ... Therefore, you'd still need to run ecryptfs-mount-private and supply your password/passphrase in order to decrypt and mount your home directory or otherwise, you won't be able to use your current home directory.
