Re: UUID

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Author: Michael Havens
Date:  
To: Main PLUG discussion list
Subject: Re: UUID
so then why did his virtual machine not look at the partitions as UUIDs but
rather as /dev/sd?? ?

:-)~MIKE~(-:

On Tue, Dec 30, 2014 at 9:29 PM, James Mcphee <> wrote:

> Hrmph, I guess you don't need one these days. I'm working off an old
> system that's been upgraded since the bronze age.
>
> https://www.gnu.org/software/grub/manual/html_node/Device-map.html
>
> On Tue, Dec 30, 2014 at 9:13 PM, Michael Havens <> wrote:
>
>> I suppose not..... so where are UUID and logical addresses kept?
>>
>> :-)~MIKE~(-:
>>
>> On Tue, Dec 30, 2014 at 9:04 PM, Michael Havens <> wrote:
>>
>>> 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 <> 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 <>
>>>> 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 <>
>>>>> 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
>>>>
>>>>
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>>>
>>>
>>
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>
>
>
> --
> James McPhee
>
>
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