I am checking different video resolutions in the grub menu by using videotest and vbetest programs and can't go back to the grub command line, after using this programs. System doesn't respond - like hanging. Only Virtualbox's poweroff the machine helps. Question: How exit from this mode? May be I use this programs wrong way?My actions:Enters to the grub menu, while booting, then go to the command mode.Run videotest 800x600  Look at the new resolution example  Then, after pressing any key, system stops respond and I can't go back to the grub menu. Get this screen: 
How exit from videotest in the grub?
virtualbox;grub2