Re: Corrupted output on errors

Hi John,

On 18/11/2021 16:28, John Goerzen wrote:
> Thank you, Denis.  I can confirm that the newer version fixed the issue.
> 
> I have uploaded 2.7.2 to Debian's bullseye-backports and after review it
> should be available to users of Debian stable.

Nice! Thanks for them :)

> 
> Now that this is cleared up, I can see the errors:
> 
> Restoration of FSA for /bakfs/other-backups/dar/ada/var/log/sysstat aborted: Skipping backward is not possible on a pipe
> Error while restoring data: Error while reading FSA from archive: Reached end of file before all data could be read
> Final memory cleanup...
> Error while restoring data: Error while reading FSA from archive: Reached end of file before all data could be read
> 
> It then exits with error 5.
> 
> This archive was generated by dar 2.6.13 on a Raspberry Pi running ext4 and unpacked
> by 2.7.2 on x86_64 running ZFS.

This error can come from a corrupted transfer between hosts or from dar
itself (bug). Could you thus:
- check that the backup testing (dar -t <backup>) succeeds with dar
2.6.13 on Raspberry?
- make a sha1 sum of the dar backup on Raspberry?
- check this sha1 sum against the dar backup on the x86_64
- test the backup on x86_64 (dar -t <backup>) using dar 2.7.2 ?

This should clarify whether the problem comes from dar or not.

> 
> The extraction command was:
> 
> dar --dirty-behavior no-warn --sequential-read -w -x - -R /bakfs/other-backups/dar/ada
> 
> And it was generated with:
> 
> Running dar -q -c - --aux /var/local/dar/1637242636 -A \
> /var/local/dar/1637182897 -R /baksnap --empty-dir \
> --retry-on-change 0 -P run -P tmp -P proc -P sys -P dev \
> -P var/tmp -P var/cache/apt/archives -P media -P mnt \
> -P cdrom -P var/cache/apt -P var/lib/mlocate -P var/lib/apt/lists \
> -P var/log/journal -P var/spool/nncp -P var/local/dar \
> -P var/cache/apt -P mythmount -P */no-backup -P home/*/.cache \
> -P var/log/*log

Thanks for that, I have no Rapberry board to test with, but I will check
this configuration between a 32 bits and 64 bits Debian OS.

> 
> There was no reference to var/log/sysstat at generation time, though I
> did get a number of messages like this:
> 
> SECURITY WARNING! SUSPICIOUS FILE /baksnap/var/spool/anacron/cron.monthly: ctime changed since archive of reference was done, while no other inode information changed
> SECURITY WARNING! SUSPICIOUS FILE /baksnap/var/spool/anacron/cron.weekly: ctime changed since archive of reference was done, while no other inode information changed
> 

This warning shows when you do differential backup and dar suspects file
to have been modified with the intention to hide the modification...
this is an heuristic that may give false positive. You can disable it
adding the -asecu option on command-line, but in anycase it does not
impact the backup content.

> - John
> 
> 

Cheers,
Denis