UUID

[Michael Havens]

well I thought to myself that I should investigate the file before asking
any questions but:

 cat /boot/grub/device.map
cat: /boot/grub/device.map: No such file or directory

I then reasoned that I would play the <tab><tab> game and see what the
files were in /boot/grub .

grub.cfg  grubenv

so I suppose it is grub.cfg?

:-)~MIKE~(-:

On Tue, Dec 30, 2014 at 8:27 PM, James Mcphee <jmcphe at gmail.com> wrote:

> /boot/grub/device.map keeps things mapped by logical location and uuid.
>  if you created a new partition, even if it had the same UUID, it would
> have a different logical address.
>
> On Tue, Dec 30, 2014 at 7:41 PM, Michael Havens <bmike1 at gmail.com> wrote:
>
>> better yet could someone come explain it to us:
>>
>> http://www.bleepingcomputer.com/forums/t/561405/new-partition-scheme/page-2#entry3582631
>>
>> :-)~MIKE~(-:
>>
>> On Tue, Dec 30, 2014 at 7:38 PM, Michael Havens <bmike1 at gmail.com> wrote:
>>
>>> I'm part of another discussion in which we are talking about UUIDs.
>>> This is what one of the participants said:
>>>
>>> As pointed out earlier by bmike1 in response to my comment about GRUB2
>>> not being able to find the OS if you move the partitions, by default on
>>> Linux Mint GRUB2 will use UUIDs *(the id tag for your partitions)* instead
>>> of partition numbers*(eg: sda1, sda2, etc)*, so I was incorrect when I
>>> said GRUB2 won't be able to find the boot partition. Linux Mint's fstab *(a
>>> config file read at boot to tell Mint which partitions should be
>>> automatically mounted)* also uses UUIDs by default so no issues there.
>>> Therefore I do not see any reason why moving your installation would be an
>>> issue *(keep reading)*, so I decided to test it in a virtual machine. I
>>> installed Linux Mint 17.1 - Cinnamon 64bit *(I've been wanting to try
>>> Linux Mint for a while. I've been downloading a little bit of the ISO each
>>> day)* with a partition layout similar to yours *(http://i.imgur.com/3qg0bSv.png
>>> <http://i.imgur.com/3qg0bSv.png> )*. I wasn't able to move the extended
>>> partition using Gparted, or create a new one. In the end I just created 3
>>> new primary partitions and cloned the Linux Mint logical partitions to them
>>> using dd *(dd is a sector based cloning tool that comes pre-installed
>>> on most Linux operating systems. I used it because this way the new
>>> partitions will have the same UUIDS as the Linux Mint ones did. This is
>>> important since GRUB2 is using UUIDS to identify the boot partition and
>>> because the fstab uses UUIDs to identify your swap partition)*. Then I
>>> deleted the old partitions *( http://i.imgur.com/hDBT5ns.png
>>> <http://i.imgur.com/hDBT5ns.png> )*. The result was that GRUB2 was
>>> unable boot Linux Mint because it couldn't find the boot partition *(I
>>> don't know why this is, but if I had to take a guess it would be that GRUB2
>>> was probably storing part of itself on the extended partition's VBR which
>>> no longer exists because I deleted the extended partition)*. So GRUB2
>>> needed to be repaired. Using a Linux Mint Live-cd, I ran "sudo
>>> add-apt-repository ppa:yannubuntu/boot-repair"*(this adds a third party
>>> repo that has boot-repair in it, because it's not available in the default
>>> Linux Mint repos)*, "sudo apt-get update" *(to update apts package
>>> list)*, "sudo apt-get install boot-repair" *(to download and install
>>> boot-repair)*, and then I ran boot-repair with its default settings *(be
>>> warned by default boot-repair uploads information about your computer
>>> online, you can disable this)*. This successfully fixed GRUB2, and I
>>> was able to boot Linux Mint again *(http://i.imgur.com/ZJhXRbe.png
>>> <http://i.imgur.com/ZJhXRbe.png> )*.
>>>
>>> I then said:
>>>
>>> I think I know why it needed repairing. The reason is that you created
>>> new partitions (new UUIDs) and deleted the old partitions (the existing
>>> UUIDs).
>>>
>>> to which he responded:
>>>
>>> The partitions were cloned with dd so that they would have the same
>>> UUIDs. I also used "sudo blkid" to verify the uuids of the new primary
>>> partitions matched before deleting the original logical partitions.
>>>
>>> He and I both remarked between the first and last quote that we thought
>>> the UUID of the partition would of had it recognized regardless of what we
>>> did with other partitions on the drive. Could someone kindly explain to us
>>> wherein the difficulties lie?
>>> :-)~MIKE~(-:
>>>
>>
>>
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>
>
>
> --
> James McPhee
> jmcphe at gmail.com
>
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