All is clear now.
Thank you so much for your detailed reply.


On 16/3/2023 8:54 π.μ., Rob Sheldon wrote:
There is no reason to be concerned. This is normal.

Searching for "backuppc pool hashing chain" finds 
https://sourceforge.net/p/backuppc/mailman/message/20671583/ for example. The documentation could 
perhaps be more specific about this, but BackupPC "chains" hash collisions, so no data is 
lost or damaged. This is a pretty standard compsci data structure. If you search the BackupPC 
repository for the message you're seeing, you find 
https://github.com/backuppc/backuppc/blob/43c91d83d06b4af3760400365da62e1fd5ee584e/lib/BackupPC/Lang/en.pm#L311,
 which gives you a couple of variable names that you can use to search the codebase and satisfy 
your curiosity.

"165 repeated files with longest chain 1" just means that there are 165 
different files that had a digest (hash) that matched another file. This can happen for a 
number of different reasons. A common one is that there are identical files on the 
backuppc client system that have different paths.

I've been running BackupPC for a *long* time and have always had chained hashes 
in my server status. It's an informational message, not an error.

On Tue, Mar 14, 2023, at 12:41 PM, Giannis Economou wrote:
The message appears in "Server Information" section, inside server
status, in the web interface of BackupPC (page "BackupPC Server Status").

Both servers are running BackupPC version 4.4.0.
1st server says:  "Pool hashing gives 165 repeated files with longest
chain 1"
2nd server says:  "Pool hashing gives 5 repeated files with longest chain 1"

I could not find more info/details about this message in the documentation.
Only a comment in github is mentioning this message, and to my
understanding it is related to hash collisions in the pool.

Since hash collisions might be worrying (in theory), my question is if
this is alarming and in that case if there is something that we can do
about it (for example actions to zero out any collisions if needed).


Thank you very much.
_</email>_
Rob Sheldon
Contract software developer, devops, security, technical lead


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