I am planning to upgrade the system compact flash in an ASA5520. Once I install the new flash, I am left without an OS to boot from. Is there an alternative to tftp from rommon to get the image onto the flash ?
ASA5520 has a slot for external flash card. You can copy the image to there and boot the box from external flash. After you replace internal flash, you can copy image back to it and change "boot system" statement to point back to internal flash.