btrfs problem 12.04

[Colin Law]

On 28 October 2015 at 10:54, Petter Adsen <petter at synth.no> wrote:
> On Wed, 28 Oct 2015 11:38:12 +0100
> Johnny Rosenberg <gurus.knugum at gmail.com> wrote:
>
>> My desktop computer, with Ubuntu 14.04, failed on me today, it just refuses
>> to start. I think I tried at least 40 times. I suspect the graphics card,
>> but never mind. So I went down to the… whatever it's called in Englist, a
>> place outside my apartment for storing things that are not used regularly,
>> in this case located in the cellar, and found my old laptop with Ubuntu
>> 12.04. It's been a long time since I used it, so I didn't even remember if
>> it works, but here I am now, typing this email with it.
>>
>> Anyway, I have a USB HDD for backups and so on I wanted to bring the latest
>> versions of all my documents back to this old laptop, mostly ODF files. The
>> problem is that the USB disk is formatted as btrfs, which indeed is
>> supported by Ubuntu 12.04 as well, but I get an error message that it can't
>> be mounted. It asks me to do ”dmesg | tail” and here's the result:
>>
>> ~$ dmesg | tail
>> [ 2087.311210] sd 4:0:0:0: [sdb] No Caching mode page found
>> [ 2087.311216] sd 4:0:0:0: [sdb] Assuming drive cache: write through
>> [ 2087.327918] sdb: sdb1
>> [ 2087.332476] sd 4:0:0:0: [sdb] No Caching mode page found
>> [ 2087.332482] sd 4:0:0:0: [sdb] Assuming drive cache: write through
>> [ 2087.332487] sd 4:0:0:0: [sdb] Attached SCSI disk
>> [ 2087.929468] device label Backup 2000 devid 1 transid 1253 /dev/sdb1
>> [ 2087.930331] btrfs: disk space caching is enabled
>> [ 2087.930337] BTRFS: couldn't mount because of unsupported optional
>> features (60).
>> [ 2087.948115] btrfs: open_ctree failed
>> ~$
>>
>> So it seems like it ”couldn't mount because of unsupported optional
>> features”.
>> How can I install support for those ”optional features” on Ubuntu 12.04? I
>> really need those files…
>> I'm reasonably sure the disk isn't encrypted.
>> I'm not very keen on upgrading to Ubuntu 14.04 at the moment since I now at
>> least have something that kind of works…
>
> You would need a newer kernel that has support for the btrfs features
> that are missing from the 12.04 kernel.

To get over your immediate problem you could boot off a live DVD of a
later Ubuntu and copy the data across from the stick to the hard disk.

Colin