[rhelv6-beta-list] My first experiences with RHEL6 beta

[John McNulty]

This brings me onto the reason why I don't like using UUIDs like this.
It's all fine and dandy for locating the filesystem on a functioning system:

[john at dsv03-pv1 ~]$ findfs UUID=cae1fd8f-acfd-4e46-bd96-8c893c07b54b
/dev/md0

But what about disaster recovery?  If I loose my system and have to recreate
a new filesystem during restore, maybe onto a new disk because it's a new
system in a new datacentre, then the UUID in fstab no longer matches the
filesystem in use and (in this example) the system won't boot.  I have to
jump through hoops to make it work, and if I have scores or hundreds of
systems like this then it becomes a PITA.

So what's the rational for the change?   With the old way it was easy to
just add -L /boot to mkfs and forget about it.

John


On 16 June 2010 19:36, John McNulty <johnmcn1 at googlemail.com> wrote:

>
> Ever wish you could unsend an email, seconds after you send it ... Doh!
>
> [john at dsv03-pv1 ~]$ sudo udevadm info --query=all --name=/dev/md0 | grep
> UUID
> E: MD_UUID=274ea8e2:0bd22aab:ab863ea6:f42c03cb
> E: ID_FS_UUID=cae1fd8f-acfd-4e46-bd96-8c893c07b54b            <---- HERE
> !!!
> E: ID_FS_UUID_ENC=cae1fd8f-acfd-4e46-bd96-8c893c07b54b
>
> John
>
>
> On 16 June 2010 19:35, John McNulty <johnmcn1 at googlemail.com> wrote:
>
>> On 16 June 2010 15:47, Bryan J. Smith <b.j.smith at ieee.org> wrote:
>> >
>> > Not entirely true.  In fact, that -- among other assumptions presented
>> > here -- are not at all, even for a single hard drive.  That's why all,
>> > new versions of major distros have changed to UUID and other references,
>> > and _away_ from legacy, fixed devices.
>>
>> Yes I noticed this and I'm not sure I like it.  For example on a test
>> rhel6 build I have a UUID for /boot
>>
>> [john at dsv03-pv1 ~]$ grep UUID /etc/fstab
>> UUID=cae1fd8f-acfd-4e46-bd96-8c893c07b54b /boot                   ext3
>>  defaults        1 2
>>
>>
>> But where is it getting this from?  It's not the UUID for the filesystem
>> or (in my case) the md raid device underneath. e.g.
>>
>> [john at dsv03-pv1 ~]$ sudo udevadm info --query=all --name=/dev/sda1 | grep
>> UUID
>> E: ID_FS_UUID=274ea8e2-0bd2-2aab-ab86-3ea6f42c03cb
>> E: ID_FS_UUID_ENC=274ea8e2-0bd2-2aab-ab86-3ea6f42c03cb
>> E: MD_UUID=274ea8e2:0bd22aab:ab863ea6:f42c03cb
>> E: MD_DEV_UUID=117ed612:97cea2cd:2d80c66d:52ade163
>>
>> John
>>
>>
>
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