Give me some examples of using recovery mode with linux ?

Try to rescue mode F5

As an examples when its  impossible to start  linux OS due to :

forgiven password.

corrupted file system .

full disk .

problem is graphical interface (X11).

For these reasons we use rescue or recovery mode.

if you means tools so we have :

1- R-Studio Clic

2- knoppix Clic

3-Trinity Rescue Kit Clic

4-GParted Live Clic

5-SystemRescueCd Clic

6-Ubuntu Rescue Remix Clic