[tlug] Computer fails to boot

["David Bernat" <dbernat@example.com>]

I get a message stating

init: unable to execute "/bin/sh" for rc-default: Permission denied
init: rc-default main process (****) terminated with status 255
-------------------------------------------------------------
**** refers to a four-digit numeral that varies at each reboot.

Is there a way to get back to a functioning system?