How can I edit the lightdm.conf file and save it?

Question

I was searching for login screens like mac and I got this one

MAC OSX LOGIN SCREEN

I did everything correctly and suddenly I was told to edit

/etc/lightdm/lightdm.conf

I opened the file in gedit and I changed it but I couldn't save it - I got the error "you do not have permission to edit this file". I saw from the permissions that only root has permission to edit it, so I ran

sudo su 

which logged me in as root, but I was still not able to complete the edit.

How can I edit and save this file?

Solution

You can use gedit or nano (among others) as below

sudo nano /etc/lightdm/lightdm.conf
sudo -H gedit /etc/lightdm/lightdm.conf

Then Ctrl+S for gedit or Ctrl+O for name to save your edits.

Either will do fine, the only difference is that nano is a terminal-based editor while gedit has its own GUI.