Many Linux newbies are confused by this when they see it, usually from a fsck. They're prompted and given a root shell, when they don't really know what the problem is.
It's simple to
resolve. Usually just
# fsck /dev/some_partition. For example,
# fsck /dev/hda5. Yes, it's also a good idea to
remember what
partition is what.
fsck it, it will
prompt you for things, and
usually it's
safe to
blindly say
yes to
everything. Lost
data will be
sent to the
partition's "
lost+found"
directory. Lost files are sorted by
inode rather than what its
filename was, so it's a good idea to use the
file command to figure out what kind of
data it is. If
file just comes up with "
filename: Data" or the like, try opening it with a few common programs such as
vi,
ee,
StarOffice,
whatever.