[Box Backup] "WARNING: Found conflicting parent ID for file ID"

[Yang Zhang]

On Wed, Apr 27, 2011 at 1:13 AM, Chris Wilson <chris at qwirx.com> wrote:
> Hi Yang,
>
> On Tue, 26 Apr 2011, Yang Zhang wrote:
>
>> I'm seeing the following on my (Ubuntu 10.04) client using the Ubuntu
>> package of boxbackup-client:
>>
>> Apr 26 19:02:21 zs bbackupd[14805]: WARNING: Found conflicting parent ID
>> for file ID 5508939
>> (/home/yang/.local/share/Trash/files/pod2/mockup/.git/objects/pack/pack-75d4956d5386619cc4fe7dc1160e500cad5486af.pack):
>> expected 226184 but found 229226 (same directory used in two different
>> locations?)
>
> [...]
>>
>> I'm wondering if I need to be concerned about this.
>
> Yes, because it's likely that Box Backup will "detect" a rename that never
> happened, and start moving files around in your backup. The data will still
> be there, but it might be difficult for you to find it when it comes to
> restore.
>
> To find out if this has affected you already, please run a test restore.
> It's a good idea to run these regularly.
>
>> I found this thread:
>>
>> http://lists.boxbackup.org/pipermail/boxbackup/2009-February/004972.html
>>
>> but it never quite got to the point of explaining the above (unless I'm
>> missing something).
>
> The most common cause is that you are backing up the same directory in more
> than one backup location. This can happen even if it's not obvious, for
> example if you use bind mounts (mount --bind) or mount the same filesystem
> twice on Linux (which does the same thing, transparently).
>
> The second most common cause is probably that there's something weird about
> the filesystem that you're backing up, and it has duplicate or changing
> inode numbers. This can happen with smbfs and various virtual/encrypting
> filesystems for example.
>
> Do either of these apply in your case? Can we see your configuration file?
>
> I notice that some of the files you're backing up have hard links (e.g. the
> git repositories). This is currently unsupported with Box Backup and will
> produce this problem. I'm not sure whether to deliberately exclude all files
> with multiple hard links with a big loud warning message, or allow people to
> do it in the knowledge that the results may well be incorrect. I think I'll
> just add a warning for now.

I'm not mounting volumes like that (just checked) and I have no
duplicate locations in my config, but I wouldn't be surprised to find
hard links (and I do have a bunch of git repos - surprised that only
one of them is showing this problem).

After leaving things running, the only thing that has been
consistently showing up as a warning is the git one - the others just
appear once and go away.  I'm assuming these transient warnings aren't
worth worrying about.  And it sounds like the worst that will happen
isn't data loss but file renames (or duplicate/hard-linked files
showing up in only one place instead of all its linked paths - I guess
this could be problematic, but I'd rather wait for that to become
supported by Box Backup :).

Running a test restore is a good idea - I'll give that a go.

>
> Cheers, Chris.
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-- 
Yang Zhang
http://yz.mit.edu/