I am trying to install from the live DVD. My system is already partitioned with LVM, and a grub boot. I tried access the LVM partitions from the Live DVD with the command:
lvchange -a y system
This activated my LVM volume named "system", but for some reason it also unmounted the live DVD. This left me in a environment where no unix commands where available, including the shutdown and mount commands.
I do not know why lvchange is unmounting the cdrom, but it is definitely an error for the DVD not to be locked. I should not be able to unmount the DVD while it is in use...
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I found the problem was not the lvchange command, but the fact that my very next commant was mount commant to /mnt. It turns out that unlike most live DVD's and CD's, that the mount is done to /mnt/livecd and then symbolic links are done to that location. This unfortunately means is someone mounts to /mnt the system is dead. A very simple way to fix this would be to mount to somewhere like /.livedvd instead, as someone is not going to instictively mount to a hidden directory named /.livedvd. Even better, do a mount --rebind on a subdirectory, so the directory is locked by the kernel as being in use.