UUID

[James Mcphee]

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 <bmike1 at gmail.com> wrote:

> I suppose not..... so where are UUID and  logical addresses kept?
>
> :-)~MIKE~(-:
>
> On Tue, Dec 30, 2014 at 9:04 PM, Michael Havens <bmike1 at gmail.com> 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 <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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>>
>>
>
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-- 
James McPhee
jmcphe at gmail.com
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