I have looked through several posts, but cannot piece together enough that I feel relates directly to my need, so i will ask in a new thread. If there is a good answer elsewhere which I have missed, please point me there.
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I have just recovered from a long episode of failure upgrading to 12.10, by reverting to a new, fresh install of 12.04.

I downloaded the .iso twice, and burnt 2 LiveCDs, but got the same results. First time, I upgraded from 12.04, second time I wiped the disk and did a fresh install, but alas, nothing but a grub prompt.

When I couldn't boot into 12.10, I downloaded and ran boot-repair, and had subsequent conversation with Yann. The core problem was that I had no kernel, and the thought was advanced that perhaps my .iso or LiveCD were corrupt.
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I still want to move to 12.10, but I would like to verify the checksum. What I don't know is whether I need to verify the checksum of the .iso image (which I no longer have), or of the LiveCD itself.

Is there a howto somewhere that I can follow through the steps of verifying a checksum?

Thanks in advance,
Daniel