During the "install" phase of the upgrade there was a power failure. After when starting up again the following errors are reported:
init: udevtrigger main process (420) terminated with status 1 init: udevtrigger post-stop process (428) terminated with status 1 init: udevmonitor main process (419) killed by TERM signal The disk drive for / is not ready yet or not present Continue to wait; or press S to skip mounting or M for manual recovery
Pressing M gives me the following message:
Root filesystem check failed. A maintenance shell will now be started. CONTROL-D will terminate this shell and reboot the system.