Exit/save edit to sudoers file? Putty SSH

Just open file by nano /file_name

Once done, press CTRL+O and then Enter to save. Then press CTRL+X to return.

Here CTRL+O : is CTRL and O for Orange Not 0 Zero

The tutorial you saw was telling you how to exit nano editor. By typing Ctrl+X nano exits and if your file needs change you will be prompted to save the changes in which case to save you should press Y and then enter to save changes in the same file you open.

If you are not using any gui and you just want to leave the shell the command is Ctrl+D.

Regarding tutorial, The Linux Documentation Project would be a good place to start. If you like books I would recommend by far any book you want from O'Reilly. They have nice cd bookshelfs with good compilation for any linux sysadmin, and without much effort you can find many places where those html bookshelfs are available to read online.

To make changes to sudo from putty/bash:

• Type visudo and press enter.
• Navigate to the place you wish to edit using the up and down arrow keys.
• Press insert to go into editing mode.
• Make your changes - for example: user ALL=(ALL) ALL.
• Note - it matters whether you use tabs or spaces when making changes.
• Once your changes are done press esc to exit editing mode.
• Now type :wq to save and press enter.
• You should now be back at bash.
• Now you can press ctrl + D to exit the session if you wish.

#UBUNTU20

if you are opening this file as root, then type

root# visudo

the file will be opened, go to the line where you want to add/modifiy anything simply without any insert or i button pressed.

press ctrl + O
press ctrl + x
press enter