Re: cross-platform backup tool Same files from different source dir causes spurious diff files

On 2/8/22 1:05 AM, Mr. Clif wrote:
> Hey folks,
> 
> thanks for the feedback. :-) More comments below...
> 
> On 2/7/22 8:25 PM, Robert Nichols wrote:
>> On 2/7/22 7:23 PM, Leland Best wrote:
>>> Hi Cliff,
>>>
>>> On Mon, 2022-02-07 at 11:45 -0800, Mr. Clif wrote:
>>>> Hey Eric,
>>>>
>>>> any ideas on this? How do these diff files normally work?
>>> [...]
>>>
>>> I'm not an 'rdiff-backup' developer or anything so all you experts out there
>>> correct me if I'm wrong but ...
>>>
>>> IIRC 'rdiff-backup' keeps inode info as part of the metadata for each file.
>>> When you mount a filesystem Linux assigns "fake" inode numbers to avoid
>>> collisions between filesystems on different devices/partitions/etc.. So if you
>>> change the mount point, every file could potentially get a new inode number and,
>>> consequently, have changed metadata.  That results in 'rdiff-backup' creating a
>>> '*.diff*' file for every source file.
>>
>> Device and inode metadata is kept only for files with multiple hard links. That's
>> to keep track of which links reference the same file. That information is not
>> needed for files with just a single hard link, and unless something has changed
>> in the latest release that metadata is not kept. You can look in the
>> mirror_metadata file (it's compressed ASCII) and see what fields are present
>> for each file.
> 
> Cool, these are the diff.gz files? I tried ungzipping them but the first "line" of data still seems to be binary. Is it encoded somehow?

No, I'm talking about the files named "mirror_metadata..." in the rdiff-backup-data
directory itself. Those are gzip-ed ASCII files that hold the principal metadata
for every file in the mirror. The most recent will have a name that ends in
".snapshot.gz". The one for the previous backup date will most likely have a
name ending in ".diff.gz", but is also a gzip-ed ASCII file that contains the
metadata for every file that was somehow different then than it is in the
latest backup. You can look at those files and see what was somehow "different".

-- 
Bob Nichols     "NOSPAM" is really part of my email address.
                 Do NOT delete it.