Undo in vim, vi, how to undo the changes in linux, ubuntu

If we open a file using 'vim' or vi we can undo the changes by pressing 'u' key on the keyboard.

For example:

vi example (enter)

After changing some content if you want to undo the changes simply press 'u' bottom. By pressing 'u' button again and agian it will automatically undo the changes in last 10 sec.

Note: 'vi' must not be insert mode. If it is in insert mode press escape ( esc on keyboard) and press 'u' button on keyboard.