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Re: drive names and UUIDs, was Re: Intresting dd fsck grub uuid fstab action





-------- Original Message --------
From: deblis@xxxxxxxxxxxxxxxxx
To: debian-user@xxxxxxxxxxxxxxxx

On Thu 01 Jun 2017 at 12:24:28 (-0400), Fungi4All wrote:

> Why don't just skip all this that we are in perfect agreement with and go to the juicy part.
> After all uuids are unique and fstab are all correct, updating-grub would mix match uuids in writing
> its grub.cfg
> Two uuids on the same entry! Over and over again.... till I edited it out to the correct ones and it all worked.
> Why does everyone choses to skip on this issue and keeps explaining me over and over
> what I have well understood by now?

Well, we don't have a lot of evidence. But we do have a tiny bit:

Ι was waiting to see if anyone else found something like this significant and willing to contribute some wisdom
I suspect the experiment would be simple.
Let's say we make a new partition on a disk with a debian installed system and use dd to clone that system in
the new partition (I have no idea whether doing this in the same disk or a second one makes a difference),
Let's say that dd copies uuid to the new partition so we have two partitions with the same uuid in the same system.
Intentionally we make the mistake and log in to the original system and update-grub with the conflict.
Then relogin and create new uuids for the clone, edit ftstab and check original, then update-grub.
Will it boot having the first root or the clone root?  Then look at grub.cfg of the original to see if the uuids for each
entry are matching or there is a mismatch.
I went through the grub manual and didn't come up with an answer.  It smells like a tiny bug or room for improvement.
Also, I believe that when dd is used to copy something from disk to disk it should provide an option of whether to
produce a new uuid or retain the original (backup, not a concurrent system).


if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos3 --hint-efi=hd0,msdos3 --hint-baremetal=ahci0,msdos3 --hint='hd0,msdos3' UUID on sda3 XXX
else
search --no-floppy --fs-uuid --set=root UUID on sda3 YYY
fi