F12-i386-DVD iso won't burn properly -- SOLVED

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Tony Nelson wrote:

> That test often fails due to a kernel issue, making good media seem
> bad.  I prefer to compare the bits with:

>     # cmp /dev/dvd /path/to/iso

> If the dvd matches the iso:  if there is no kernel issue there will
> be no output; else it will complain about eof on the iso file.  If
> the dvd does not match the iso, there will be a specific complaint
> about the first mismatch.

Reading /dev/dvd in general is not reliable since depending on the
hardware, it may not read exactly the right number of bytes (hopefully,
it will at least read >= the right number, which means your command
would either give an EOF error if the number was greater, or say the
files are identical if it's the same).

I use the rawread script from

http://www.troubleshooters.com/linux/coasterless.htm#rawread

which automatically reads the correct size of the ISO, and runs a dd
command reading exactly that much off the disc.  This way I can just
check the hash directly, like this:

rawread /dev/dvd | sha256sum

which only requires reading the optical disc.

To deal with the linux readahead bug, the ISO must be zero-padded before
burning.  Cdrecord/wodim has such an option (see the above page).
Instead, I use the isopad script at

http://ftp.cs.utoronto.ca/pub/hugh/isopad

I put both the rawread and isopad scripts in ~/bin with execute
permissions so they're available as regular commands.  My burning
procedure is:

1) Download DVD ISO, check its hash.
2) Pad the ISO with "isopad + dvd.iso".
3) Burn with command

growisofs -dvd-compat -speed=1 -Z /dev/dvd=dvd.iso

(preferably as root on an unloaded machine to give it every advantage).

4) Verify the burn with "rawread /dev/dvd | sha256sum" (should give the
hash of the UNpadded ISO), or do a mediacheck.

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