how to backup git

how to backup git

[bill lam]

Hello, this should be a simple question. How to backup a git repository but 
excluding files that not under versioned?  If I cp or tar or rsync the 
directory. All non-versioned files are added.

regards,

Re: how to backup git

[Tobias Sarnowski]

Hi bill,

Backing up the ".git" directory is all you need. You can also clone it  
as a bare repository (see git clone --bare).

Afterwards "git checkout" is your friend.

Tobias

Am 12.05.2008 um 08:08 schrieb bill lam <cbill.lam@gmail.com>:

> Hello, this should be a simple question. How to backup a git  
> repository but excluding files that not under versioned?  If I cp or  
> tar or rsync the directory. All non-versioned files are added.
>
> regards

Re: how to backup git

[Sverre Hvammen Johansen]

bill lam <cbill.lam <at> gmail.com> writes:

> Hello, this should be a simple question. How to backup a git repository but 
> excluding files that not under versioned?  If I cp or tar or rsync the 
> directory. All non-versioned files are added.

A repository can be backed up by backing up the .git directory.

If you want to back up the HEAD commit, use git-archive as follows:

  $ git archive --prefix=my-backup/ HEAD | gzip >my-backup.tar.gz

If you want to back up the working directory, commit it to a temporary branch
before you use 'git archive'.

-- 
Sverre Hvammen Johansen

Re: how to backup git

[Eric Hanchrow]

>>>>> "bill" == bill lam <cbill.lam@gmail.com> writes:

    bill> Hello, this should be a simple question.  How to backup a git
    bill> repository but excluding files that not under versioned?  If I
    bill> cp or tar or rsync the directory.  All non-versioned files are
    bill> added.

I'd rsync just the .git directory.

-- 
It sounds churlish to bash a film that's as bereft of bad
thoughts as a tiny puppy.  But when the puppy licks your face for 108
minutes, enough's enough.
        -- Matt Zoller Seitz, NY Times

Re: how to backup git

[Johannes Schindelin]

Hi,

On Mon, 12 May 2008, Eric Hanchrow wrote:

> >>>>> "bill" == bill lam <cbill.lam@gmail.com> writes:
> 
>     bill> Hello, this should be a simple question.  How to backup a git
>     bill> repository but excluding files that not under versioned?  If I
>     bill> cp or tar or rsync the directory.  All non-versioned files are
>     bill> added.
> 
> I'd rsync just the .git directory.

Note that this is necessary if you want to keep the reflogs (clone would 
not copy them).

Ciao,
Dscho

Re: how to backup git

[bill lam]

Johannes Schindelin wrote:
 >> I'd rsync just the .git directory.

Thanks to all responders for quick reply. I still have a related question. svn 
has a hotcopy command to ensure integrity so that it is possible to backup 
without shutting down the svn server. If someone update the .git while I am 
performing backup using tar or rsync? Will the atomicity of that commit still 
preserve in my backup copy?

regards,

Re: how to backup git

[Miklos Vajna]

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On Mon, May 12, 2008 at 10:13:27PM +0800, bill lam <cbill.lam@gmail.com> wrote:
> Thanks to all responders for quick reply. I still have a related question. 
> svn has a hotcopy command to ensure integrity so that it is possible to 
> backup without shutting down the svn server. If someone update the .git 
> while I am performing backup using tar or rsync? Will the atomicity of that 
> commit still preserve in my backup copy?

the only problem can be when someone runs git-gc (as it runs git-prune)
while you are doing the backup. other commands never remove objects.

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Re: how to backup git

[Johannes Schindelin]

Hi,

[please do not cull the Cc: list]

On Mon, 12 May 2008, bill lam wrote:

> Johannes Schindelin wrote:
> > > I'd rsync just the .git directory.
> 
> Thanks to all responders for quick reply. I still have a related 
> question. svn has a hotcopy command to ensure integrity so that it is 
> possible to backup without shutting down the svn server. If someone 
> update the .git while I am performing backup using tar or rsync? Will 
> the atomicity of that commit still preserve in my backup copy?

No, rsync is particularly dumb in that respect.  The safest thing would be 
to back up the reflogs first (e.g. with rsync), then repack and then clone 
(the clone will transmit the objects referenced by the reflogs, too).  
Note: the same holds _not_ true for a simple fetch.

But then, you usually do not want to back up reflogs anyway, since they 
are purely local and not visible to anybody else.

Ciao,
Dscho

Re: how to backup git

[Heikki Orsila]

On Mon, May 12, 2008 at 04:08:21PM +0100, Johannes Schindelin wrote:
> No, rsync is particularly dumb in that respect.  The safest thing would be 
> to back up the reflogs first (e.g. with rsync), then repack and then clone 
> (the clone will transmit the objects referenced by the reflogs, too).  
> Note: the same holds _not_ true for a simple fetch.
> 
> But then, you usually do not want to back up reflogs anyway, since they 
> are purely local and not visible to anybody else.

Is there a simple and efficient mechanism for incremental backups?
It should be safe with respect to simultaneous repository access.
Incrementals should be efficient weven when a user runs "git gc". 
Preferably I would like to have one file per day: 
myrepo.YYYY-MM-DD.increment (and occasionally myrepo.YYYY-MM-DD.full)
I believe this is a common administration problem; 
something like "git-backup" script/tool would be nice so that not all 
the admins need consider these issues.

Currently, I'm doing daily clones of repos, and I preserve those cloned 
directories.

-- 
Heikki Orsila
heikki.orsila@iki.fi
http://www.iki.fi/shd

Re: how to backup git

[Johannes Schindelin]

Hi,

On Mon, 12 May 2008, Heikki Orsila wrote:

> On Mon, May 12, 2008 at 04:08:21PM +0100, Johannes Schindelin wrote:
> > No, rsync is particularly dumb in that respect.  The safest thing 
> > would be to back up the reflogs first (e.g. with rsync), then repack 
> > and then clone (the clone will transmit the objects referenced by the 
> > reflogs, too).  Note: the same holds _not_ true for a simple fetch.
> > 
> > But then, you usually do not want to back up reflogs anyway, since 
> > they are purely local and not visible to anybody else.
> 
> Is there a simple and efficient mechanism for incremental backups?

Umm.  "git fetch"?

Like I said, it does not get the reflogs, but if you want to back up a 
repository, the safest is to clone once, and fetch later.  Or you could 
set up a remote with the --mirror option, if you want to preserve the 
refs' namespaces.

Ciao,
Dscho

Re: how to backup git

[Heikki Orsila]

On Mon, May 12, 2008 at 06:07:28PM +0100, Johannes Schindelin wrote:
> Hi,
> 
> On Mon, 12 May 2008, Heikki Orsila wrote:
> 
> > On Mon, May 12, 2008 at 04:08:21PM +0100, Johannes Schindelin wrote:
> > > No, rsync is particularly dumb in that respect.  The safest thing 
> > > would be to back up the reflogs first (e.g. with rsync), then repack 
> > > and then clone (the clone will transmit the objects referenced by the 
> > > reflogs, too).  Note: the same holds _not_ true for a simple fetch.
> > > 
> > > But then, you usually do not want to back up reflogs anyway, since 
> > > they are purely local and not visible to anybody else.
> > 
> > Is there a simple and efficient mechanism for incremental backups?
> 
> Umm.  "git fetch"?
> 
> Like I said, it does not get the reflogs, but if you want to back up a 
> repository, the safest is to clone once, and fetch later.  Or you could 
> set up a remote with the --mirror option, if you want to preserve the 
> refs' namespaces.

Preferably some solution that does not require too much understanding of 
Git internals so that admins will actually use it, instead of hacking 
their own inefficient backup scripts.

Could someone please write a "git-backup" script?-)

-- 
Heikki Orsila
heikki.orsila@iki.fi
http://www.iki.fi/shd

Re: how to backup git

[Johannes Schindelin]

Hi,

On Mon, 12 May 2008, Heikki Orsila wrote:

> On Mon, May 12, 2008 at 06:07:28PM +0100, Johannes Schindelin wrote:
> 
> > On Mon, 12 May 2008, Heikki Orsila wrote:
> > 
> > > On Mon, May 12, 2008 at 04:08:21PM +0100, Johannes Schindelin wrote:
> > > > No, rsync is particularly dumb in that respect.  The safest thing 
> > > > would be to back up the reflogs first (e.g. with rsync), then 
> > > > repack and then clone (the clone will transmit the objects 
> > > > referenced by the reflogs, too).  Note: the same holds _not_ true 
> > > > for a simple fetch.
> > > > 
> > > > But then, you usually do not want to back up reflogs anyway, since 
> > > > they are purely local and not visible to anybody else.
> > > 
> > > Is there a simple and efficient mechanism for incremental backups?
> > 
> > Umm.  "git fetch"?
> > 
> > Like I said, it does not get the reflogs, but if you want to back up a 
> > repository, the safest is to clone once, and fetch later.  Or you 
> > could set up a remote with the --mirror option, if you want to 
> > preserve the refs' namespaces.
> 
> Preferably some solution that does not require too much understanding of 
> Git internals so that admins will actually use it, instead of hacking 
> their own inefficient backup scripts.
> 
> Could someone please write a "git-backup" script?-)

Heikki, why don't you just go with the "git fetch" approach I described?  
We do not need "git backup" when "git fetch" does already what you want.

Ciao,
Dscho

Re: how to backup git

[Heikki Orsila]

On Mon, May 12, 2008 at 07:21:02PM +0100, Johannes Schindelin wrote:
> Heikki, why don't you just go with the "git fetch" approach I described?  
> We do not need "git backup" when "git fetch" does already what you want.

I need efficient (small) daily increment files. What I could do is 
something like:

1. rm -rf yesterday ; mv today yesterday

2. git clone yesterday today

3. cd today && git fetch /path/to/repo

4. create an increment file (from yesterday to today) or a full

The above should just be something like (why not make this easy?):

1. git backup /path/to/repo /backup/location/

And restoration should be something like:

1. git backup --restore /backup/location/foo /path/to/repo

Am I missing something?

-- 
Heikki Orsila
heikki.orsila@iki.fi
http://www.iki.fi/shd

Re: how to backup git

[Heikki Orsila]

On Mon, May 12, 2008 at 09:36:15PM +0300, Heikki Orsila wrote:
> 3. cd today && git fetch /path/to/repo

That was a mistake, a bare fetch is not enough.

-- 
Heikki Orsila
heikki.orsila@iki.fi
http://www.iki.fi/shd

Re: how to backup git

[Jakub Narebski]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> On Mon, 12 May 2008, Heikki Orsila wrote:
> 
>> On Mon, May 12, 2008 at 06:07:28PM +0100, Johannes Schindelin wrote:
>> 
>>> On Mon, 12 May 2008, Heikki Orsila wrote:
 
>>>> Is there a simple and efficient mechanism for incremental backups?
>>> 
>>> Umm.  "git fetch"?
>>> 
>>> Like I said, it does not get the reflogs, but if you want to back up a 
>>> repository, the safest is to clone once, and fetch later.  Or you 
>>> could set up a remote with the --mirror option, if you want to 
>>> preserve the refs' namespaces.
>> 
>> Preferably some solution that does not require too much understanding of 
>> Git internals so that admins will actually use it, instead of hacking 
>> their own inefficient backup scripts.
>> 
>> Could someone please write a "git-backup" script?-)
> 
> Heikki, why don't you just go with the "git fetch" approach I described?  
> We do not need "git backup" when "git fetch" does already what you want.

I think that bundles (see git-bundle) would be what you want (please
read GitFaq/GitTips/"Git in Nutshell" for explanation and use cases).

"git fetch" (perhaps using bundle) would save state of refs (heads,
remote branches, tags) and object repository.  To save state of
working area and index I think it would be best to use 'git-stash'
before creating backup, and unstash after it; see documentation for
git-stash.  What is left is: reflogs, configuration, hooks, grafts and
shallow, repository local excludes file, repository local attributes
file[*1*].

[*1*] Which is not mentioned in Documentation/repository-layout.txt
-- 
Jakub Narebski
Poland
ShadeHawk on #git

Re: how to backup git

[Tim Harper]

On May 12, 2008, at 12:38 PM, Heikki Orsila wrote:

> On Mon, May 12, 2008 at 09:36:15PM +0300, Heikki Orsila wrote:
>> 3. cd today && git fetch /path/to/repo
>
> That was a mistake, a bare fetch is not enough.

Yeah, Heikki - I wonder if you're missing the point.  In our case, we  
don't bother with repository backups here.  Everyone developer has a  
full copy of the repository, and any one of them could be used to  
create a new "central" git repository.  If our central git repository  
goes down - we've got 9 others floating around on different laptops  
and computers.  You can't beat that kind of redundancy.  You'd have to  
nuke Utah to take us out (btw: please don't nuke Utah).

Tim

>
>
> -- 
> Heikki Orsila
> heikki.orsila@iki.fi
> http://www.iki.fi/shd
> --
> 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 backup git

[Heikki Orsila]

On Mon, May 12, 2008 at 12:58:07PM -0600, Tim Harper wrote:
> In our case, we  
> don't bother with repository backups here.  Everyone developer has a  
> full copy of the repository, and any one of them could be used to  
> create a new "central" git repository.

So you assume everyone syncs everyone else often enough. I don't think 
many organizations want to rely on that assumption. The point is to 
have a simple, efficient and manageable backup system that 
does _not_ require knowledge of Git internals.

-- 
Heikki Orsila
heikki.orsila@iki.fi
http://www.iki.fi/shd

Re: how to backup git

[Sverre Rabbelier]

On Mon, May 12, 2008 at 9:10 PM, Heikki Orsila <shdl@zakalwe.fi> wrote:
>  So you assume everyone syncs everyone else often enough. I don't think
>  many organizations want to rely on that assumption. The point is to
>  have a simple, efficient and manageable backup system that
>  does _not_ require knowledge of Git internals.

Isn't that what Dscho and others have mentioned a few times now?
Initially you git clone the repo, every few hours you have cron do a
git pull and daily you do 'rm yesterday.tar.gz && mv today.tar.gz
yesterday.tar.gz && tar czvf today.tar.gz .git '. Why would git need a
'backup script' for something so trivial? I reckon everybody wants a
different type of backup too, so creating a 'git backup' would
probably not be very usefull to most.

-- 
Cheers,

Sverre Rabbelier

Re: how to backup git

[Daniel Barkalow]

On Mon, 12 May 2008, bill lam wrote:

> Johannes Schindelin wrote:
> > > I'd rsync just the .git directory.
> 
> Thanks to all responders for quick reply. I still have a related question. svn
> has a hotcopy command to ensure integrity so that it is possible to backup
> without shutting down the svn server. If someone update the .git while I am
> performing backup using tar or rsync? Will the atomicity of that commit still
> preserve in my backup copy?

There's the risk that the backup will start, it will copy all of the 
objects, then a git commit happens, which adds more objects (after rsync 
has passed) and updates a "refs" entry to refer to one of them, and then 
rsync copies the "refs" directory.

It's likewise possible to have part of the information for a commit copied 
and part of it not. This commit will be clearly broken, however (one or 
more objects not found). 

So, essentially, every commit goes through the stages of not at all 
written, partially written but invalid, and valid and correct. 
Independantly, which commit is the latest is updated atomically. It's 
possible for an ill-timed backup to get a branch updated to a commit 
that's not yet valid in the backup. In you restored from this, you'd need 
to use one of several methods (mainly reflogs) to get back to the last 
valid commit that got backed up.

On the other hand, git will never, even in this sort of backup, end up 
with a commit that's valid but not completely correct.

	-Daniel
*This .sig left intentionally blank*

Re: how to backup git

[Junio C Hamano]

Daniel Barkalow <barkalow@iabervon.org> writes:

> On Mon, 12 May 2008, bill lam wrote:
>
>> Johannes Schindelin wrote:
>> > > I'd rsync just the .git directory.
>> 
>> Thanks to all responders for quick reply. I still have a related question. svn
>> has a hotcopy command to ensure integrity so that it is possible to backup
>> without shutting down the svn server. If someone update the .git while I am
>> performing backup using tar or rsync? Will the atomicity of that commit still
>> preserve in my backup copy?
>
> There's the risk that the backup will start, it will copy all of the 
> objects, then a git commit happens, which adds more objects (after rsync 
> has passed) and updates a "refs" entry to refer to one of them, and then 
> rsync copies the "refs" directory.
>
> It's likewise possible to have part of the information for a commit copied 
> and part of it not. This commit will be clearly broken, however (one or 
> more objects not found). 
>
> So, essentially, every commit goes through the stages of not at all 
> written, partially written but invalid, and valid and correct. 
> Independantly, which commit is the latest is updated atomically. It's 
> possible for an ill-timed backup to get a branch updated to a commit 
> that's not yet valid in the backup. In you restored from this, you'd need 
> to use one of several methods (mainly reflogs) to get back to the last 
> valid commit that got backed up.
>
> On the other hand, git will never, even in this sort of backup, end up 
> with a commit that's valid but not completely correct.

I think suggestions from old timers on this thread to first "git fetch" is
to handle that concern.  It may not get the commit that is being created
simultaneously when such a fetch to backup repository is running (but that
will be backed up during the next round), but at least the contents of the
backup repository would be self contained and correct.  So a nightly fetch
(perhaps with --mirror) into a backup repository, and then after the fetch
finishes, copying the backup repository to tape, would give you one copy a
night.  Copying out from the central repository to backup repository would
be incremental, and until you repack the backup repository, the tape
backup of that backup repository could also be made incremental, as fetch
will be append-only into its objects/ part with updates to refs/ part.

Re: how to backup git

[Daniel Barkalow]

On Mon, 12 May 2008, Junio C Hamano wrote:

> Daniel Barkalow <barkalow@iabervon.org> writes:
> 
> I think suggestions from old timers on this thread to first "git fetch" is
> to handle that concern.

Yeah, "git fetch" is the right solution (although it's a pain to do a 
backup of "every repo under <path>" or "every repo anywhere under <path>" 
that way, which I suspect of being the real issue). I just wanted to get a 
note into this thread of what problems using rsync can and cannot have, 
since it's different (both more and less reliable) from what the original 
poster asked about.

> It may not get the commit that is being created simultaneously when such 
> a fetch to backup repository is running (but that will be backed up 
> during the next round), but at least the contents of the backup 
> repository would be self contained and correct.

And simultaneous commit isn't really an issue; nothing will back up work 
you do right after the backup runs, and users can't tell whether they did 
the commit before or after the backup if it's close.

	-Daniel
*This .sig left intentionally blank*