Re-initializing the internal hard drive
WARNING: This will wipe out *everything* on the internal hard drive, and (hopefully) restore the DS-101 to a working state. It *does* depend on some libraries in /lib, so if you've messed around too much there, it won't work. The solution then is to take out the hdd and remove the partitions on some other PC. Formatting the drive in Windows or OSX for example is an easy way to "reset" the drive so it will format again in a DS101.
(If you still have telnet access)