drive configuration changes on reboot; blkid.tab defeats UUIDs
 

I had cause to reboot my gentoo box this morning, and it was an
unexpected disaster.
For some reason, my two PCI-X SATA controllers decided to switch
places in the /dev/sd* lists.
My /etc/fstab had explicit drive paths hard-coded, and they tried to
mount stuff that
didn't exist, and naturally failed. I wound up in a root shell under
instructions to clean this
up.

I decided to go with UUIDs in /etc/fstab. After a half-hour or so
pfutzing around with these
(how do you find the UUID of an unmounted partition when you're not
even really sure
what kind of filesystem it has), I got everything to mount with "mount
-a", and I rebooted.

The drives had changed names again, the sort of thing that UUIDs were
designed to
deal with, but the mount command was stubbornly using the old names.
Bootup failed and
I was back in a root shell. Thank goodness my root directory is still
on an HDA drive.
But where did these names come from -- they weren't in /etc/fstab any
more. I did a system
call trace on mount(1) to find out.

There's a file I never heard of or noticed before: /etc/blkid.tab, and
a backup, that seem to
override the UUIDs, putting us back in the world we were in before
Labels and UUIDs.

Grrrr.

I can get a good boot if I rm blkid.tab and its backup before I shut down.

So:

1) Can I disable blkid.tab? In the presence of UUIDs this seems sensible.
2) Does anyone know if labels are also defeated? I don't feel like
rebooting any more
today just to find out.
3) Can we just stop this madness somehow?

++ kevin

--
Kevin O'Gorman, PhD
--
gentoo-user@lists.gentoo.org mailing list

drive configuration changes on reboot; blkid.tab defeats UUIDs
 

Kevin O'Gorman schrieb:

I had cause to reboot my gentoo box this morning, and it was an
unexpected disaster.
For some reason, my two PCI-X SATA controllers decided to switch
places in the /dev/sd* lists.
My /etc/fstab had explicit drive paths hard-coded, and they tried to
mount stuff that
didn't exist, and naturally failed. I wound up in a root shell under
instructions to clean this
up.

I decided to go with UUIDs in /etc/fstab. After a half-hour or so
pfutzing around with these
(how do you find the UUID of an unmounted partition when you're not
even really sure
what kind of filesystem it has), I got everything to mount with "mount
-a", and I rebooted.

The drives had changed names again, the sort of thing that UUIDs were
designed to
deal with, but the mount command was stubbornly using the old names.
Bootup failed and
I was back in a root shell. Thank goodness my root directory is still
on an HDA drive.
But where did these names come from -- they weren't in /etc/fstab any
more. I did a system
call trace on mount(1) to find out.

There's a file I never heard of or noticed before: /etc/blkid.tab, and
a backup, that seem to
override the UUIDs, putting us back in the world we were in before
Labels and UUIDs.

Grrrr.

I can get a good boot if I rm blkid.tab and its backup before I shut down.

So:

1) Can I disable blkid.tab? In the presence of UUIDs this seems sensible.
2) Does anyone know if labels are also defeated? I don't feel like
rebooting any more
today just to find out.
3) Can we just stop this madness somehow?

++ kevin



I have never heard of this before too. So i tried something like this:

blkid -c /dev/null -w /etc/blkid.tab

Which should drop the old blkid.tab and create new one from scratch. See
'man blkid' for reference. I want to do this because my blkid.tab has
also some entries which are obsolete. This did not work as expected,
after a search i found that the -w switch is not working for quite some
time now [1].

So i moved both the /etc/blkid.tab and /etc/blkid.tab.old to somewhere
else and simply run blkid and a new correct /etc/blkid.tab and
/etc/blkid.tab.old have been created.

I have not rebooted yet, but I don't expect much trouble with this changes!

Regards,

Daniel

[1] http://lists.openwall.net/linux-ext4/2008/03/02/2
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gentoo-user@lists.gentoo.org mailing list

drive configuration changes on reboot; blkid.tab defeats UUIDs
 

On Monday 07 July 2008, Kevin O'Gorman wrote:

> I decided to go with UUIDs in /etc/fstab. After a half-hour or so
> pfutzing around with these
> (how do you find the UUID of an unmounted partition when you're not
> even really sure
> what kind of filesystem it has),

blkid
part of e2fsprogs

> There's a file I never heard of or noticed before: /etc/blkid.tab,
> and a backup, that seem to
> override the UUIDs, putting us back in the world we were in before
> Labels and UUIDs.

It's just a cache, see 'man blkid'

You can safely delete it, or use 'blkid -c <filename>' to use a
different cache, or 'blkid -c /dev/null' to ignore it.

I suspect your troubles come down to mount using a blkid with data from
before your controller decided to go all postal on you

> 3) Can we just stop this madness somehow?

You could just use volume labels - a poor man's UUID scheme where you
get to invent your own unique names

--
Alan McKinnon
alan dot mckinnon at gmail dot com

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