I created a bucket on BackBlaze.
I run the following command from my Mac: restic -r b2:mybucket:s3:s3.eu-central-003.backblazeb2.com init
I receive the following error:
Fatal: create repository at b2:mybucket:s3:s3.eu-central-003.backblazeb2.com failed: Fatal: unable to open repository at b2:mybucket:s3:s3.eu-central-003.backblazeb2.com: Fatal: unable to open B2 backend: Account ID ($B2_ACCOUNT_ID) is empty
Due to issues with error handling in the current B2 library that restic uses, the recommended way to utilize Backblaze B2 is by using its S3-compatible API.
B2 supports two different API - B2 native and industry standard S3. For reasons mentioned in docs looks like S3 is preferred by restic.
You have to get S3 credentials - ACCESS_KEY and SECRET_ACCESS_KEY. How exactly I am not sure as I do not use B2:) But I am sure you can google it easily.
Then you export both keys and connect to S3, as per docs: