Backing up BTRFS metadata

Backing up BTRFS metadata

[Marat Khalili]

Sorry if question sounds unorthodox, Is there some simple way to read 
(and backup) all BTRFS metadata from volume?

Motivation of course is possibility to quickly recover from catastrophic 
filesystem failures on a logical level. Some small amount of actual data 
that this metadata references may be overwritten between backup and 
restore moments, but due to checksumming it can easily be caught (and 
either individually restored from backup or discarded).

--

With Best Regards,
Marat Khalili

Re: Backing up BTRFS metadata

[Chris Murphy]

On Thu, May 11, 2017 at 8:56 AM, Marat Khalili <mkh@rqc.ru> wrote:
> Sorry if question sounds unorthodox, Is there some simple way to read (and
> backup) all BTRFS metadata from volume?

btrfs-image



-- 
Chris Murphy

Re: Backing up BTRFS metadata

[Marat Khalili]

On 11/05/17 18:19, Chris Murphy wrote:
> btrfs-image
Looks great, thank you!

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With Best Regards,
Marat Khalili

Re: Backing up BTRFS metadata

[Roman Mamedov]

On Thu, 11 May 2017 09:19:28 -0600
Chris Murphy <lists@colorremedies.com> wrote:

> On Thu, May 11, 2017 at 8:56 AM, Marat Khalili <mkh@rqc.ru> wrote:
> > Sorry if question sounds unorthodox, Is there some simple way to read (and
> > backup) all BTRFS metadata from volume?
> 
> btrfs-image

Hm, I thought that's for debugging only, and that you can't actually restore
metadata onto a data-containing FS and have anything mountable/readable as a
result.

Seems not to be the case, and in fact, could this be one of the "missing
links" in the Fsck story, 

       -w
           Walk all the trees manually and copy any blocks that are
           referenced. Use this option if your extent tree is corrupted to
           make sure that all of the metadata is captured.

This certainly does sound like something to try for some of those broken
filesystems where Btrfsck refuses to do anything. Save image with this manual
walking/reconstruction of the trees, then restore. Too bad I already nuked
mine, so can't experiment with that.

-- 
With respect,
Roman

Re: Backing up BTRFS metadata

[Hugo Mills]

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On Fri, May 12, 2017 at 12:22:00AM +0500, Roman Mamedov wrote:
> On Thu, 11 May 2017 09:19:28 -0600
> Chris Murphy <lists@colorremedies.com> wrote:
> 
> > On Thu, May 11, 2017 at 8:56 AM, Marat Khalili <mkh@rqc.ru> wrote:
> > > Sorry if question sounds unorthodox, Is there some simple way to read (and
> > > backup) all BTRFS metadata from volume?
> > 
> > btrfs-image
> 
> Hm, I thought that's for debugging only, and that you can't actually restore
> metadata onto a data-containing FS and have anything mountable/readable as a
> result.

   Indeed. This has been tried before, and I don't think it came to
anything.

> Seems not to be the case, and in fact, could this be one of the "missing
> links" in the Fsck story, 
> 
>        -w
>            Walk all the trees manually and copy any blocks that are
>            referenced. Use this option if your extent tree is corrupted to
>            make sure that all of the metadata is captured.
> 
> This certainly does sound like something to try for some of those broken
> filesystems where Btrfsck refuses to do anything. Save image with this manual
> walking/reconstruction of the trees, then restore. Too bad I already nuked
> mine, so can't experiment with that.

   I suspect it's still only capturing metadata, rather than data.

   Hugo.

-- 
Hugo Mills             | Would you like an ocelot with that non-sequitur?
hugo@... carfax.org.uk |
http://carfax.org.uk/  |
PGP: E2AB1DE4          |

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Re: Backing up BTRFS metadata

[Marat Khalili]

>     Indeed. This has been tried before, and I don't think it came to
> anything.
What can/did go wrong?


>     I suspect it's still only capturing metadata, rather than data.
Yes. But data should still be there, on disk, right?


--

With Best Regards,
Marat Khalili