Unable to mount (or, why not to work late at night).

Unable to mount (or, why not to work late at night).

[Ken D'Ambrosio]

So, I was trying to downgrade my Ubuntu last night, and, before doing anything
risky like that, I backed up my disk via dd to an image on an external disk. 
The critical part here is that I'm afraid I did something truly stupid: I'm
afraid I did the dd... live.  (I can't swear to this, and it does seem
unlikely, but it also seems to be the most likely circumstance.)

So, I dd'd everything back, and now it crashes on boot.  Booting to a 2.6.x
kernel (which is what I had on-hand on a USB drive) mounts it, but doesn't let
me *do* anything (though it spews btrfs errors in dmesg).  Getting Ubuntu 11.10
(kernel rev. 3.0.0) gives me this:

[  121.226246] device fsid d657ce6a-d353-4c2c-858a-6a1f4d9e766e devid 1 transid
217713 /dev/sda1
[  121.232430] parent transid verify failed on 100695031808 wanted 217713 found
217732
[  121.232898] parent transid verify failed on 100695031808 wanted 217713 found
217732
[  121.233357] parent transid verify failed on 100695031808 wanted 217713 found
217732
[  121.233365] parent transid verify failed on 100695031808 wanted 217713 found
217732
[  121.248231] btrfs: open_ctree failed

As I have this complete image on-disk, I'm more than willing to try Extreme
Measures(tm), whatever that might entail.  If I can't get it back, it's not
like it's the loss of my job or anything, but there *is* stuff I'd really like
to get back.

Thanks,

-Ken

Re: Unable to mount (or, why not to work late at night).

[Helmut Hullen]

Hallo, Ken,

Du meintest am 27.10.11:

> So, I dd'd everything back, and now it crashes on boot.  Booting to a
> 2.6.x kernel (which is what I had on-hand on a USB drive) mounts it,
> but doesn't let me *do* anything (though it spews btrfs errors in
> dmesg).  Getting Ubuntu 11.10 (kernel rev. 3.0.0) gives me this:

> [  121.226246] device fsid d657ce6a-d353-4c2c-858a-6a1f4d9e766e devid
> 1 transid 217713 /dev/sda1
> [  121.232430] parent transid verify failed on 100695031808 wanted
> 217713 found 217732
> [  121.232898] parent transid verify failed on 100695031808 wanted
> 217713 found 217732
> [  121.233357] parent transid verify failed on 100695031808 wanted
> 217713 found 217732
> [  121.233365] parent transid verify failed on 100695031808 wanted
> 217713 found 217732
> [  121.248231] btrfs: open_ctree failed

It may not please you - I have the same problem. Kernel 3.1.

The first try to mount is in "/etc/rc.d/rc.local". Has worked many  
weeks, now doesn't work. Without any message.

Next try produces (in "dmesg")

device label MMedia devid 2 transid 57932 /dev/sdb1
parent transid verify failed on 21094400 wanted 57401 found 47987
parent transid verify failed on 21094400 wanted 57401 found 47987
parent transid verify failed on 21094400 wanted 57401 found 47987
parent transid verify failed on 21094400 wanted 57401 found 47987
parent transid verify failed on 21094400 wanted 57401 found 47987
btrfs: failed to read chunk tree on sdg1
btrfs: open_ctree failed

And the third try has success:

device label MMedia devid 2 transid 57932 /dev/sdb1

----------------------------------------

Very few times I don't need 3 tries, but only 2.

---------------------------------------------------------------

What's the meaning of the 3 numbers in the "parent" message?

Viele Gruesse!
Helmut

Re: Unable to mount (or, why not to work late at night).

[Fajar A. Nugraha]

On Thu, Oct 27, 2011 at 10:22 PM, Ken D'Ambrosio <ken@jots.org> wrote:
> So, I was trying to downgrade my Ubuntu last night, and, before doing=
 anything
> risky like that, I backed up my disk via dd to an image on an externa=
l disk.

some of us make use of snapshot/clone, whether it's using btrfs or zfs =
:)

> So, I dd'd everything back, and now it crashes on boot. =A0Booting to=
 a 2.6.x
> kernel (which is what I had on-hand on a USB drive) mounts it, but do=
esn't let
> me *do* anything (though it spews btrfs errors in dmesg).

What do you mean don't let you do anything? Can you mount it read-only
and copy the data off the disk?

> =A0Getting Ubuntu 11.10
> (kernel rev. 3.0.0) gives me this:

I'd try 3.1. If you use 11.10 try
http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.1-oneiric/

>
> [ =A0121.226246] device fsid d657ce6a-d353-4c2c-858a-6a1f4d9e766e dev=
id 1 transid
> 217713 /dev/sda1
> [ =A0121.232430] parent transid verify failed on 100695031808 wanted =
217713 found
> 217732
> [ =A0121.232898] parent transid verify failed on 100695031808 wanted =
217713 found
> 217732
> [ =A0121.233357] parent transid verify failed on 100695031808 wanted =
217713 found
> 217732
> [ =A0121.233365] parent transid verify failed on 100695031808 wanted =
217713 found
> 217732
> [ =A0121.248231] btrfs: open_ctree failed

> As I have this complete image on-disk, I'm more than willing to try E=
xtreme
> Measures(tm), whatever that might entail.

Try getting source of btrfs-progs, do "make btrfs-zero-log", and use it=
=2E

--=20
=46ajar
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Re: Unable to mount (or, why not to work late at night).

[Ken D'Ambrosio]

> some of us make use of snapshot/clone, whether it's using btrfs or zfs :)

No, this is just flat my fault: it doesn't matter what backup method you use if
you do it wrong.  (I actually have three snapshots of each of my two
partitions.)

> What do you mean don't let you do anything? Can you mount it read-only
> and copy the data off the disk?

You can mount it on the older kernels, but, once you try any form of access,
you can watch your load spike as it spews errors into dmesg.

> I'd try 3.1. If you use 11.10 try
> http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.1-oneiric/

3.1 is what the system had been running; it simply panics when trying to mount
the FS.

> Try getting source of btrfs-progs, do "make btrfs-zero-log", and use it.

Already got 'em.  Everything that tries to even think about modifying stuff
(btrfs-zero-log, btrfsck, and btrfs-debug-tree) all dump core:

root@ubuntu:/tmp/btrfs-progs# ./btrfs-zero-log /dev/sda1
parent transid verify failed on 100695031808 wanted 217713 found 217732
parent transid verify failed on 100695031808 wanted 217713 found 217732
parent transid verify failed on 100695031808 wanted 217713 found 217732
btrfs-zero-log: disk-io.c:413: find_and_setup_root: Assertion '!(!root->node)'
failed.
Aborted (core dumped)


-Ken

Re: Unable to mount (or, why not to work late at night).

[dima]

On 10/28/2011 09:32 AM, Ken D'Ambrosio wrote:
>> some of us make use of snapshot/clone, whether it's using btrfs or zfs :)
>
> No, this is just flat my fault: it doesn't matter what backup method you use if
> you do it wrong.  (I actually have three snapshots of each of my two
> partitions.)
>
>> What do you mean don't let you do anything? Can you mount it read-only
>> and copy the data off the disk?
>
> You can mount it on the older kernels, but, once you try any form of access,
> you can watch your load spike as it spews errors into dmesg.
>
>> I'd try 3.1. If you use 11.10 try
>> http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.1-oneiric/
>
> 3.1 is what the system had been running; it simply panics when trying to mount
> the FS.

Hello Ken,

Personally I would be very afraid to go from 3.1 to 2.6.x. There should 
be no incompatible changes, but still I would expect all sorts of 
trouble and instability at the very least. There are a few mount options 
that were added in 3.x and that will not work with older kernels. Might 
be you are hitting those as well if you used them (just wild guessing 
without any real grounds).

I would try getting the latest live CD with 3.1 from somewhere and try 
to mount your various snapshots from there. You might as well be lucky 
and be able to mount some of your snapshots.
The repair program from this list would be your last resort I think (

~d

Re: Unable to mount (or, why not to work late at night).

[Fajar A. Nugraha]

On Fri, Oct 28, 2011 at 7:32 AM, Ken D'Ambrosio <ken@jots.org> wrote:
>> some of us make use of snapshot/clone, whether it's using btrfs or z=
fs :)
>
> No, this is just flat my fault: it doesn't matter what backup method =
you use if
> you do it wrong. =A0(I actually have three snapshots of each of my tw=
o
> partitions.)

What I meant was, if you use snapshot you can easily rollback, and not
having to dd-back. But you're right though, it doesn't matter what you
use if you do it wrong.

>> Try getting source of btrfs-progs, do "make btrfs-zero-log", and use=
 it.
>
> Already got 'em. =A0Everything that tries to even think about modifyi=
ng stuff
> (btrfs-zero-log, btrfsck, and btrfs-debug-tree) all dump core:

Your last resort (for now, anyway) might be using "restore" from
Josef's btrfs-progs: https://github.com/josefbacik/btrfs-progs

It might be able to copy some data.

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=46ajar
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Re: Unable to mount (or, why not to work late at night).

[Stephane CHAZELAS]

2011-10-28, 07:57(+07), Fajar A. Nugraha:
[...]
>> Already got 'em. =C2=A0Everything that tries to even think about mod=
ifying stuff
>> (btrfs-zero-log, btrfsck, and btrfs-debug-tree) all dump core:
>
> Your last resort (for now, anyway) might be using "restore" from
> Josef's btrfs-progs: https://github.com/josefbacik/btrfs-progs
>
> It might be able to copy some data.

I also have got one FS in that same situation. I tried
everything on it including that "restore" (which bailed out with
those same error messages IIRC).

The only thing that got me a bit further was to use an alternate
superblock, though that screwed the FS even further as I need to
reboot the machine after trying to mount it (mount hangs and
there are some btrfs tasks using all the CPU time).

=46ortunately, for that one, I had a not too old backup at the
block device level.

--=20
Stephane

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Re: Unable to mount (or, why not to work late at night).

[Dave]

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Hash: SHA256

On Thu, Oct 27, 2011 at 08:32:09PM -0400, Ken D'Ambrosio wrote:
> root@ubuntu:/tmp/btrfs-progs# ./btrfs-zero-log /dev/sda1
> parent transid verify failed on 100695031808 wanted 217713 found 217732
> parent transid verify failed on 100695031808 wanted 217713 found 217732
> parent transid verify failed on 100695031808 wanted 217713 found 217732
> btrfs-zero-log: disk-io.c:413: find_and_setup_root: Assertion '!(!root->node)'
> failed.

This is the same bullshit I dealt with back in August.  In short, your data is
likely fine.  btrfs is preventing you from accessing your data because there is
something wrong with the csum tree.  My solution was to create a custom kernel
which ignored all checksums.  I was then able to mount the filesystem read-only
and copy data to another volume.

http://thread.gmane.org/gmane.comp.file-systems.btrfs/12344

I've had this happen to me on two occasions.  The first time was after a hard
reboot.  The second was on a totally different machine at a different geographic
location, which occurred after nothing more than a reboot.
- -- 
- -=[dave]=-

Entropy isn't what it used to be.
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