Hi, I'm trying to fix tarsnap service on NixOS[1] and I have several questions regarding cache directories.
As experimentally discovered in [1], tarsnap breaks when using separate cache directories. I'm not yet sure if this is an intended behavior or we do something the wrong way. A short summary of the problem: 1. User (me) has several tarsnap configurations with different cache directories and one common key file. 2. Run `tarsnap --fsck` for configurations foo and bar; 3. Run `tarsnap -c --configfile foo`, observe that it works; 4. Run `tarsnap -c --configfile bar`, observe that it fails; 5. Run `tarsnap --fsck --configfile bar`; 6. Run `tarsnap -c --configfile bar`, observe that it works now; 7. Run `tarsnap -c --configfile foo`; observe that it's broken. The error in all cases is "Sequence number mismatch". From that I can conclude that tarsnap doesn't support separate cache directories -- is it correct? Generally, our NixOS module supports creating several tarsnap configurations with different key files and other settings, which are given separate cache directories. The first fix that I thought of was to instead use one common cache directory. But what if a user has configurations with different keys? Is it okay to use the same cache directory in this case? One last thing -- when I run tarsnap given an empty cache directory, it fails. Do I understand correctly that if I want to use a cache directory, I should first run `--fsck` on it to fill it for the first time? Last but not least, I want to use this chance to thank Colin and tarsnap contributors for their awesome work on this product. You are the best! -- Nikolay. 1: https://github.com/NixOS/nixpkgs/issues/15948