Comment 15 for bug 234185

Looking closer at cdrom-detect (which probably would need to be replaced by something like "detect-media") is that it does not iterate through devices. It really assumes there is one CD available. It just picks the first that satisfies a rough "cdrom" criteria, and then goes on to verify that single device. Just adding "list-devices usb-partition" would just grab the first USB drive's first partition (it will check for real CD devices first though). If there are several USB drives and partitions and it picks the wrong, it is stuck. Like Colin already mentioned, this is a problem if you want to install to another USB drive.

Similarly in the current situation, if there are two CDs, and only one is a Ubuntu CD, it fails if it happens to detect another CD first.

I therefore adjusted cdrom-detect.postinst to check for .disk/info each time it tries to mount a "CD" drive. See https://code.launchpad.net/~tormodvolden/cdrom-detect/usb-drive-install