Does rsync detect file corruption?

[Christian Hecht]

Thank you Wayne for pointing me to these patches. I've never noticed  
them before.


Am 24.05.2009 um 23:53 schrieb Wayne Davison:

> On Sun, May 24, 2009 at 06:32:40PM +0200, Christian Hecht wrote:
>> Such a tool i plan to write for Mac OS X. The first time it should
>> store checksums and mod times for all files to verify.
>
> There are various patches in the "patches" dir that deal with cached
> checksums in different ways:
>
> - checksum-reading.diff & checksum-updating.diff -- both of these  
> use a
>   special file in each dir to store the checksums, with the latter
>   putting code into rsync to be able to update the file when copying
>   the files (both have a perl script to build/update the files and
>   check checksums against the file).
>
> - checksum-xattr.diff -- this has a script that puts checksums into an
>   xattr field which rsync can access when it is using the --checksum
>   option.  The very latest version of this patch (in git) adds a -- 
> list
>   and --check option to the script.
>
checksum-xattr.diff -This seems to be a good option for me but i'm a  
not sure how to use it exactly.

- First i run the xsum script which generates all the checksums an  
stores it in the xattrs
- Then i use rync which can compare the stored checksums with the  
actual new generated checksum, right? I assume if the checksums are  
different, there will be some message in log. But if a file has  
changed meanwhile, the checksum also will be different. How can rsync  
distinguish between these caes?
- To update the stored checksums, i have to use the xsum script again?  
But if a file is corrupted, the checksum also will be updated?

Best regards
Christian

> - db.diff -- this is the start of some db-accessing code for rsync  
> that
>   can be used to store/access/check checksums (supports sqlite and
>   mysql at present).  This is the method I like the best, but the code
>   is in an early state that needs more work.
>
> ..wayne..