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what is the difference when a hard drive is mounted and when it is unmounted?

erm...
When a hard drive is mounted, you can access it through the VFS, when it isn't you can't.

ie. /dev/hda1 is a device, unless you want to read it byte by byte it isn't very useful. But you can mount it, "mount -t reiserfs /dev/hda1 /mnt/hda1" then you can access the contents via /mnt/hda1/*. It's also useful to note that you should always umount removal media since that also flushes the buffer (since writes aren't neccessarily atomic)

dude, that was probably the last place to ask. this is not a LUG. tnx.