Cannot manage to get borgbackup working via Nixos options

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1

I switched my server to Nixos and wanted to continue my backup setup with borg backup by setting it up in the configuration.nix. This is the interesting section:

  services.borgbackup.jobs.borgbackup = {
    paths = "/home/computer/data/";
    encryption = {
      mode = "repokey-blake2";
      passphrase = "mysecretpassword"; # I know it is world-readable
    };
    archiveBaseName = "${config.networking.hostName}--";
    dateFormat = "+%Y-%m-%d_%H:%M";
    environment.BORG_RSH = "ssh -p 69 -i /home/computer/.ssh/id_rsa";
    environment.BORG_RELOCATED_REPO_ACCESS_IS_OK = "yes";
    repo = "ssh://computer@remoteip:69/home/computer/ssd/backup";
    compression = "auto,lz4";
    user = "computer";
    startAt = "daily";
    inhibitsSleep = true;
    extraCreateArgs = "--verbose --filter AME --list --stats --show-rc --exclude-caches";
    prune.keep = {
      daily = 7;
      weekly = 4;
      monthly = 6;
    };
    extraPruneArgs = "--list --show-rc";
    preHook = "${pkgs.curl}/bin/curl https://hc-ping.com/secreturl";
    postHook = "
      if [ $exitStatus -ne 0 ]; then
        ${pkgs.curl}/bin/curl https://hc-ping.com/differentsecreturl1 \
      else
        ${pkgs.curl}/bin/curl https://hc-ping.com/differentsecreturl2 \
      fi
    ";
    failOnWarnings = true;
  };

If I manually start the service via:

sudo systemctl start borgbackup-job-borgbackup.service

and then check the log with:

sudo journalctl -fu borgbackup-job-borgbackup.service

I can see that I get the following result:

Aug 27 17:06:22 computer systemd[1]: Started BorgBackup job borgbackup.
Aug 27 17:06:22 computer borgbackup-job-borgbackup-start[1957369]: Failed to inhibit: Access denied
Aug 27 17:06:22 computer systemd[1]: borgbackup-job-borgbackup.service: Main process exited, code=exited, status=1/FAILURE
Aug 27 17:06:22 computer systemd[1]: borgbackup-job-borgbackup.service: Failed with result 'exit-code'.

I can give a borg create with no issues by giving the following command from the user computer (but before I export the PASSPHRASE and REPO_URL in the command line, the same specified in the configuration.nix above):

borg create    \
                              --verbose        \
                                  --filter AME                            \
                                  --list                                  \
                              --stats        \
                              --show-rc        \
                              --compression lz4        \
                              --exclude-caches        \
                              ::'{hostname}--{now:%Y-%m-%d_%H:%M}'    \
                              ./

I also don’t get any issue by connecting via ssh to:

ssh -v -p 69 -i /home/computer/.ssh/id_rsa computer@remoteip

Thus, I don’t understand why I cannot get borgbackup running via Nixos options…

2

Googling more I found what could be a “middle-solution” by modifying this line

environment.BORG_RSH = "ssh -p 69 -i /home/computer/.ssh/id_rsa";

into this:

environment.BORG_RSH = "ssh -o StrictHostKeyChecking=no -p 69 -i /home/computer/.ssh/id_rsa";

I don’t know if this is considered very safe but now it seems the process has started. I will see if someone comes with a better solution.