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Holger Parplies wrote:
> Hi,
>
> Michael Stucki wrote on 2008-07-23 14:27:17 +0200 [[BackupPC-users] Change
> RsyncShareName - will BackupPC reuse existing backup data?]:
>> I'm backing up a rather huge system which I had synced with rsync before.
>>
>> [...] I had to change XferMethod and RsyncShareName. [...]
>>
>> The backup seems to work will, as the data gets copied. However, since it
>> takes extremely long, I have the impression that the old backups are not
>> found anymore, and the full data is transferred again.
>>
>> I have no proof if the old data is really ignored, just think that it takes
>> way too long. Can anyone confirm this?
>
> yes, that is correct. The pooled data is re-used, i.e. no extra space is taken
> up on the BackupPC server, and even re-compression of the data is unnecessary
> (the pooled copy is found and decompressed - provided you are using
> compression, that is). But it needs to be re-transferred first. There is no
> way for BackupPC to know that the 'share' "foo" used to be named "bar", even
> if it's obvious to you, so the old contents cannot be used as a reference to
> speed up the transfer. And no, it is not possible to use the pool file as
> reference, because you need part of the file contents and the file length to
> determine the possible pool files, and by the time the BackupPC server has
> that data, it's too late to select a reference file, because the transfer of
> the file is already in progress.
>
>> Is it a bug?
>
> No.
>
>> It would have been very easy if rsyncd allows module names to be named
>> like paths, e.g. "/". However, as this doesn't work I was forced to change
>> the RsyncShareName...
>
> I'm no rsyncd expert, but I believe I've read of people using rsyncd modules
> named like paths. Aside from that, why didn't you use rsync over ssh or sudo
> instead of rsyncd for the initial local backup (of course the paths would
> still
> have to match, but maybe chroot can help there)? That seems even more
> straightforward than naming the rsyncd module according to what the real path
> is.
Could you not just rename the files/dirs in
/var/lib/backuppc/pc/hostname/0....
ie, look at your first backup you took and you should see something like
this:
/var/lib/backuppc/pc/hostname/0/fabc
where abc is the rsyncd sharename you used.
You should also see this:
/var/lib/backuppc/pc/hostname/1/f%2fhome
where /home is the rsync sharename
just rename 0/fabc to 0/f%2fhome and then run your rsync backup....
You might also need some help in modifying the attrib file, I really
don't know anything about the format of that, and it seems to be some
binary format.....
At the end of the day, the transformations that backuppc does are not
hugely complicated, and there is plenty of very good knowledge people
are willing to share on this list. If you are trying to save a few
hundred meg on a multi megabit link, then I'd suggest don't bother, it
will be easier. If you are trying to save multi-gigabyte data over a
small link, then persevere, I am sure someone will help solve the
problem for you.
BTW, I would repeat the question above, why not use ssh+rsync for your
local backup as well ?
Best of luck :)
Regards,
Adam
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