A special shell will be launched by this option with a fixit Floppy
mounted as /mnt2.  This provides access to extra commands under /mnt2
as well as a more complete set of device files in /mnt2/dev.  Some device
operations, like fsck and disklabel, may therefore require you to go to
/mnt2/dev and use the entries there rather than assuming that they will be
present in the default /dev (which came from the boot floppy and is very
minimal).

When you're done, exit the shell to reboot.
