not able of booting into rescue mode

[Chris Murphy]

FYI it's not linux rescue. It's just rescue. Add one word at the end
of the boot parameter line.

On BIOS systems, the media uses isolinux, so to edit the boot
parameter you use arrow keys to choose the boot option you want, hit
tab and the cursor should already be at the end of that line, so just
type rescue and then press enter.

On UEFI systems, the media uses GRUB2, so to edit the boot parameter
you need to use arrow keys to pick the boot option you want, hit the
letter e to edit that entry, and then use arrows to find the line
starting with linuxefi and use arrow keys to (laboriously) get to the
end of that line where you see rhgb quiet and add the word rescue.
Then you need to hit either control-x or F10 or Fn+F10 depending on
how your keyboard, firmware, and GRUB negotiate such things.

(On my Mac, it's always Fn+F10, nothing else works. On a new Dell,
it's always control-x, nothing else works. Joy.)

Chris Murphy