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

[Mr. Clif]

Hey Eric,

any ideas on this? How do these diff files normally work?

    Thanks,
    Clif

On 2/5/22 11:05 AM, Mr. Clif wrote:
> Greetings,
>
> Recently I started experimenting with backing up LVM snapshots of live 
> systems instead of the systems themselves. This protects against 
> getting complaints about files changing like:
>
> UpdateError: 
> 'clif/.mozilla/firefox/5zz41jpw.default/sessionstore-backups/recovery.baklz4' 
> Updated mirror temp file 
> '/leda.bak/home/clif/.mozilla/firefox/5zz41jpw.default/sessionstore-backups/rdiff-backup.tmp.75' 
> does not match source
>
> So for example instead of the source being the root dir of a remote 
> server, it's now /mnt/vm-backup-snapshot/ on the local server. The 
> destination is the same. The first time I tried this I got .diff and 
> .diff.gz files for pretty much every file in the filesystem. The vast 
> majority of these files are very small like 80-100 bytes. Here is a 
> sample:
>
>
> -rwxr-xr-x 1 root root 96 Feb 28  2019 
> tank-rdiff/rdiff-backup-data/increments/bin/dir.2022-02-01T05:20:43-09:00.diff.gz
> -rwxr-xr-x 1 root root 103 Mar 18  2021 
> tank-rdiff/rdiff-backup-data/increments/bin/systemctl.2022-02-01T05:20:43-09:00.diff.gz
> -rwxr-xr-x 1 root root 96 Feb 28  2019 
> tank-rdiff/rdiff-backup-data/increments/bin/touch.2022-02-01T05:20:43-09:00.diff.gz
> -rwxr-xr-x 1 root root 80 Feb 28  2019 
> tank-rdiff/rdiff-backup-data/increments/bin/rm.2022-02-01T05:20:43-09:00.diff.gz
> -rwxr-xr-x 1 root root 93 Jan 21  2019 
> tank-rdiff/rdiff-backup-data/increments/bin/run-parts.2022-02-01T05:20:43-09:00.diff.gz
> -rwxr-xr-x 1 root root 91 Feb 28  2019 
> tank-rdiff/rdiff-backup-data/increments/bin/chown.2022-02-01T05:20:43-09:00.diff.gz
> -rwxr-xr-x 1 root root 94 Mar 18  2021 
> tank-rdiff/rdiff-backup-data/increments/bin/journalctl.2022-02-01T05:20:43-09:00.diff.gz
> -rwxr-xr-x 1 root root 83 Feb 28  2019 
> tank-rdiff/rdiff-backup-data/increments/bin/sync.2022-02-01T05:20:43-09:00.diff.gz
> -rwxr-xr-x 1 root root 96 Mar 18  2021 
> tank-rdiff/rdiff-backup-data/increments/bin/systemd-escape.2022-02-01T05:20:43-09:00.diff.gz
> -rwxr-xr-x 1 root root 109 Mar 18  2021 
> tank-rdiff/rdiff-backup-data/increments/bin/systemd-tty-ask-password-agent.2022-02-01T05:20:43-09:00.diff.gz
> -rwxr-xr-x 1 root root 90 Feb 28  2019 
> tank-rdiff/rdiff-backup-data/increments/bin/false.2022-02-01T05:20:43-09:00.diff.gz
> -rwxr-xr-x 1 root root 67 Jan  5  2019 
> tank-rdiff/rdiff-backup-data/increments/bin/zforce.2022-02-01T05:20:43-09:00.diff.gz
> -rwxr-xr-x 1 root root 65 Jan  5  2019 
> tank-rdiff/rdiff-backup-data/increments/bin/znew.2022-02-01T05:20:43-09:00.diff.gz
> -rwxr-xr-x 1 root root 98 Jan 21  2019 
> tank-rdiff/rdiff-backup-data/increments/bin/tempfile.2022-02-01T05:20:43-09:00.diff.gz
>
> The total space used by this increment was around 500MB and the 
> largest file was (the only file size that had a suffix):
>
> -rw-r----- 1 root adm 2.1K Jan 22 05:21 
> tank-rdiff/rdiff-backup-data/increments/var/log/auth.log.2022-02-01T05:20:43-09:00.diff.gz
>
> I looked at some of these diff files and they seemed empty except for 
> a binary header that I didn't find documentation for in the 
> rdiff-backup file format section. I also noticed that occasionally, 
> these "empty" diffs show up in normal day to day increments. I realize 
> that diffs also can show up when the permissions change but I don't 
> think all these files changed.
>
> Is this how it's supposed to work, and could you please explain it to 
> me? :-)
>
>     Thanks,
>     Clif