Read out the chunker parameters

Getting Help
1

Greetings, everyone,

Is it possible to read out chunker parameters?
Use cases for example:

  1. The user is curious how the parameters look like.
  2. A user already initialized a 2nd repository without --copy-chunker-params and this already contains a snapshot. Now he wants to copy a snapshot from a 1st repository to the 2nd, but does not know if the chunker parameters are the same and wants to make sure that deduplication would work.

For the second use case, assume a large amount of data, a remote backup server with slow internet and similar data with many deduplication opportunities.

2

restic cat config prints out this information:

repository 6b517e47 opened (version 2, compression level auto)
{
  "version": 2,
  "id": "6b517e47687b77fa912c3e4110f66c174974fe49c0556113aa70284f77971e78",
  "chunker_polynomial": "3b525ca01d336d"
}
2 Likes
3

Thank you. :slightly_smiling_face:

With your help I found the command hidden in restic cat --help.

Features and Ideas → Getting Help

In the documetation I only found:

Content Defined Chunking (CDC): An irreducible polynomial is selected at random and saved in the file config when a repository is initialized.

I think this is the chunker_polynomial.

4

Too bad can’t change the chunker polynomial post initialization - coz with second case - if find out the polynomial is diffrent… can’t do anything about it!