How to recovery a corrupted git repo

How to recovery a corrupted git repo

[Ping Yin]

I have a corrupted git repo, with "git fsck", it shows

missing blob b71eb55f2dbc97dafd4a769fc61f346e69a5e0af
missing blob 282035f3ae964e1e288f352c370be8edd11d3078
missing tree 3c20f556eecc476e3542cc522d46a62a4461fec6
missing blob f321b578edeb452358497e832815d6cae6b36886
missing commit 6d23f5084c975be637f7d748db82116bf84d3872

And i also have a good backup repo. How can i recover the corrupted
repo with the backup repo?

I can do a rsync or fresh "git clone", however, is there any git
related commands to incrementally do this?

btw, "git remote add and then git fetch" doesn't work, it reports

error: refs/heads/bringup does not point to a valid object!
error: refs/heads/fsl_imx_r9.3 does not point to a valid object!
error: refs/heads/bringup does not point to a valid object!
error: refs/heads/fsl_imx_r9.3 does not point to a valid object!
error: refs/heads/bringup does not point to a valid object!
error: refs/heads/fsl_imx_r9.3 does not point to a valid object!
error: refs/heads/bringup does not point to a valid object!
error: refs/heads/fsl_imx_r9.3 does not point to a valid object!
error: missing object referenced by 'refs/tags/v2.6.32'
error: missing object referenced by 'refs/tags/v2.6.32-rc1'
error: missing object referenced by 'refs/tags/v2.6.32-rc2'

Re: How to recovery a corrupted git repo

[Christian Couder]

On Mon, Feb 21, 2011 at 8:50 AM, Ping Yin <pkufranky@gmail.com> wrote:
> I have a corrupted git repo, with "git fsck", it shows
>
> missing blob b71eb55f2dbc97dafd4a769fc61f346e69a5e0af
> missing blob 282035f3ae964e1e288f352c370be8edd11d3078
> missing tree 3c20f556eecc476e3542cc522d46a62a4461fec6
> missing blob f321b578edeb452358497e832815d6cae6b36886
> missing commit 6d23f5084c975be637f7d748db82116bf84d3872
>
> And i also have a good backup repo. How can i recover the corrupted
> repo with the backup repo?

Please, have a look this FAQ entry:

https://git.wiki.kernel.org/index.php/GitFaq#How_to_fix_a_broken_repository.3F

And tell us what you did according to it.

Thanks,
Christian.

Re: How to recovery a corrupted git repo

[Axel Freyn]

Hi,
On Mon, Feb 21, 2011 at 03:50:09PM +0800, Ping Yin wrote:
> I have a corrupted git repo, with "git fsck", it shows
> 
> missing blob b71eb55f2dbc97dafd4a769fc61f346e69a5e0af
> missing blob 282035f3ae964e1e288f352c370be8edd11d3078
> missing tree 3c20f556eecc476e3542cc522d46a62a4461fec6
> missing blob f321b578edeb452358497e832815d6cae6b36886
> missing commit 6d23f5084c975be637f7d748db82116bf84d3872
> 
> And i also have a good backup repo. How can i recover the corrupted
> repo with the backup repo?
> 
> I can do a rsync or fresh "git clone", however, is there any git
> related commands to incrementally do this?
I don't know whether there is a single git command to do it, but you can
copy those 5 objects "by hand": in your backup, you should have a
directory .git/objects, where you have the files
   b7/1eb55f2dbc97dafd4a769fc61f346e69a5e0af
   28/2035f3ae964e1e288f352c370be8edd11d3078
   3c/20f556eecc476e3542cc522d46a62a4461fec6
   f3/21b578edeb452358497e832815d6cae6b36886
   6d/23f5084c975be637f7d748db82116bf84d3872

It should be sufficient to just copy those files into the corrupted
repo.

However if you packed the git-files in the backup (e.g. by running "git
gc"), those objects might be found in a pack in .git/objects/pack.
The easiest ist probably to use git-unpack-objects to unpack the
objects, and then copy the 5 missing objects.

Axel

PS: Well, I'm using git and I like it -- but I'm no specialist; so first
do a backup, before you follow my proposal ;-)

Re: How to recovery a corrupted git repo

[Ping Yin]

Thanks, axel and Christian.

I am just look for a simpler method. since i have a full backup,
finally , i do something like following

git clone --bare --reference bad-repo.git foo.com:good-repo.git repo.git

On Mon, Feb 21, 2011 at 6:04 PM, Axel Freyn <axel-freyn@gmx.de> wrote:
> Hi,
> On Mon, Feb 21, 2011 at 03:50:09PM +0800, Ping Yin wrote:
>> I have a corrupted git repo, with "git fsck", it shows
>>
>> missing blob b71eb55f2dbc97dafd4a769fc61f346e69a5e0af
>> missing blob 282035f3ae964e1e288f352c370be8edd11d3078
>> missing tree 3c20f556eecc476e3542cc522d46a62a4461fec6
>> missing blob f321b578edeb452358497e832815d6cae6b36886
>> missing commit 6d23f5084c975be637f7d748db82116bf84d3872
>>
>> And i also have a good backup repo. How can i recover the corrupted
>> repo with the backup repo?
>>
>> I can do a rsync or fresh "git clone", however, is there any git
>> related commands to incrementally do this?
> I don't know whether there is a single git command to do it, but you can
> copy those 5 objects "by hand": in your backup, you should have a
> directory .git/objects, where you have the files
>   b7/1eb55f2dbc97dafd4a769fc61f346e69a5e0af
>   28/2035f3ae964e1e288f352c370be8edd11d3078
>   3c/20f556eecc476e3542cc522d46a62a4461fec6
>   f3/21b578edeb452358497e832815d6cae6b36886
>   6d/23f5084c975be637f7d748db82116bf84d3872
>
> It should be sufficient to just copy those files into the corrupted
> repo.
>
> However if you packed the git-files in the backup (e.g. by running "git
> gc"), those objects might be found in a pack in .git/objects/pack.
> The easiest ist probably to use git-unpack-objects to unpack the
> objects, and then copy the 5 missing objects.
>
> Axel
>
> PS: Well, I'm using git and I like it -- but I'm no specialist; so first
> do a backup, before you follow my proposal ;-)
>
> --
> To unsubscribe from this list: send the line "unsubscribe git" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

Re: How to recovery a corrupted git repo

[Matthieu Moy]

Axel Freyn <axel-freyn@gmx.de> writes:

> I don't know whether there is a single git command to do it, but you can
> copy those 5 objects "by hand": in your backup, you should have a
> directory .git/objects, where you have the files
>    b7/1eb55f2dbc97dafd4a769fc61f346e69a5e0af
>    28/2035f3ae964e1e288f352c370be8edd11d3078
>    3c/20f556eecc476e3542cc522d46a62a4461fec6
>    f3/21b578edeb452358497e832815d6cae6b36886
>    6d/23f5084c975be637f7d748db82116bf84d3872
>
> It should be sufficient to just copy those files into the corrupted
> repo.
>
> However if you packed the git-files in the backup (e.g. by running "git
> gc"), those objects might be found in a pack in .git/objects/pack.
> The easiest ist probably to use git-unpack-objects to unpack the
> objects, and then copy the 5 missing objects.

There's also the brute-force approach

rsync $good_repo/.git/objects/ $bad_repo/.git/objects/
cd $bad_repo
git gc

Notice the absence of --delete in the rsync command: I'm just adding
new files in the $bad_repo, not deleting any (since files with
identical names must have identical content).

This will result in a lot of duplicates (objects found in several
packs), but "git gc" should be able to remove them.

(the notice about doing backups before also applies to my
proposal ;-) )

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/

Re: How to recovery a corrupted git repo

[Ping Yin]

On Mon, Feb 21, 2011 at 10:51 PM, Matthieu Moy
<Matthieu.Moy@grenoble-inp.fr> wrote:
> Axel Freyn <axel-freyn@gmx.de> writes:
>
> There's also the brute-force approach
>
> rsync $good_repo/.git/objects/ $bad_repo/.git/objects/
> cd $bad_repo
> git gc
>
> Notice the absence of --delete in the rsync command: I'm just adding
> new files in the $bad_repo, not deleting any (since files with
> identical names must have identical content).

Thanks. This should be an applicable method. However, before rsyncing,
the pack should be unpacked first.

Re: How to recovery a corrupted git repo

[Matthieu Moy]

Ping Yin <pkufranky@gmail.com> writes:

> Thanks. This should be an applicable method. However, before rsyncing,
> the pack should be unpacked first.

No need. Just copying the pack files works too, and is way faster:

/tmp/corrupted$ git fsck
missing commit 4815c2955d5863005edc4ff61c0de42e9609a920
dangling tree c8b826f673e1f1edb0fb5dc58294148be06cd6cb
/tmp/corrupted$ cp ../cloned/.git/objects/pack/pack-e34444a471a9cd3e6f2656b609ffa0d66cce1f9c.* .git/objects/pack/
/tmp/corrupted$ git fsck                                                                                         
/tmp/corrupted$ git gc
Counting objects: 12, done.
Delta compression using up to 2 threads.
Compressing objects: 100% (4/4), done.
Writing objects: 100% (12/12), done.
Total 12 (delta 0), reused 12 (delta 0)

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/

Re: How to recovery a corrupted git repo

[Ping Yin]

On Mon, Feb 21, 2011 at 11:31 PM, Matthieu Moy
<Matthieu.Moy@grenoble-inp.fr> wrote:
> Ping Yin <pkufranky@gmail.com> writes:
>
>> Thanks. This should be an applicable method. However, before rsyncing,
>> the pack should be unpacked first.
>
> No need. Just copying the pack files works too, and is way faster:
>

Great, thanks.