[vbox-dev] Using xattrs to exclude disk images from time machine under OSX

[Andrew Melo]

Hi Klaus,

Thanks for the response.

On Fri, Sep 18, 2015 at 11:20 AM, Klaus Espenlaub
<klaus.espenlaub at oracle.com> wrote:
> Hi Andrew,
>
> On 11.09.2015 05:00, Andrew Melo wrote:
>> Hello,
>>
>> I am looking to implement enabling a setting for Virtualbox to
>> automatically set the
>> "com.apple.metadata:com_apple_backup_excludeItem" xattr for newly
>> created disk images, most probably hooked into the global/per-VM
>> extradata somewhere under the VboxInternal tree. This xattr will cause
>> time machine to ignore the file when backing up, without having to
>> manually add the directories where Virtualbox is storing the images.
>
> Sounds like a nice option to me, but not something which should happen
> unconditionally (as some people might wan to have their VMs handled by
> time machine).

Oh, of course not, I would keep the defaults as-is and a user could
choose to change the behavior if they chose.

>
>> Why don't I just add ~/Virtualbox\ VMs to the exclusion? Because
>> there's some applications which integrate kicking off a VM for
>> testing, and the images are stored next to the rest of the application
>> state.
>
> I don't follow why you think 'time machining' VM configs without the
> corresponding disk images makes any sense.

Think of the situation where you kick off a webserver in a VM, but the
files served are on host mounts. I don't care about the VM image, but
I want the other bits. (ideally the VM image would be somewhere else)

>
>> Looking through the source tree, the change looks to be
>> straightforward, but I don't want to take the time to make a patch if
>> this feature wouldn't be considered for inclusion.
>
> The real challenge from my perspective is to make this configurable in a
> sensible way. I'm almost certain that a significant number of users
> would complain if for all newly created disk images VirtualBox would
> automatically exclude them from the backup. Feel free to give arguments
> which support the opposite :)

I agree 100%, the default behavior would stay the same. I would then
implement Doing The Right Thing based on the global/per-VM setting.
(You could set it globally to not back up and then invert it on a
per-VM basis if you wanted)

>
> I do agree that the basic feature isn't complicated. The tricky part is
> finding a sensible way to configure this, as no other platform so far
> needed a similar configuration.

I think as a first pass, I'd code the actual "tell the OS to not back
this file up" logic in a way that should be abstracted for different
platforms, if they have similar functionality. In the OSX case, it's
just setting an extended attribute on the file, so it's not very
heavyweight.

>
> Thanks for your proposal, we'll see what comes out of it...

Thanks for listening. If the maintainers consider it reasonable, I'll
put a patch together implementing it.

Cheers,
Andrew

>
> Klaus
>>
>> Thanks!
>> Andrew
>>
>
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-- 
--
Andrew Melo