filesystem weirdness :(

[James Mabry]

Hey all,
I'm using Debian unstable and have been very pleased as I have not run 
into many problems...until now.

I wanted to convert my filesystems from ext2 to ext3 so to be safe I 
booted my machine with knoppix. I used tune2fs -j on /dev/hda1 (/) and 
/dev/hda6 (/home) successfully but when I tried it on /dev/hda7 (/usr) I 
got the following error:

"tune2fs: Bad magic number in super-block while trying to open /dev/hda7 
couldn't find valid filesystem superblock."

I thought I specified the wrong device but /usr is in fact /dev/hda7. I 
booted back into my normal debian install (no longer using knoppix) and 
was very surprised to see that only /dev/hda1 (/) was mounted yet I was 
still able to access /home and /usr! What's going on here :(!?!