Decisions/clanModules: Add example borgbackup as real world example
This commit is contained in:
Johannes Kirschbauer
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Mic92
Mic92
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8231979bae
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591d397df9
@@ -255,3 +255,293 @@ The following thoughts went into this:
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## Iteration note
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## Iteration note
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We want to implement the system as described. Once we have sufficient data on real world use-cases and modules we might revisit this document along with the updated implementation.
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We want to implement the system as described. Once we have sufficient data on real world use-cases and modules we might revisit this document along with the updated implementation.
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## Real world example
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The following module demonstrates the idea in the example of *borgbackup*.
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```nix
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{
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_class = "clan.service";
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# Define the 'options' of 'settings' see argument of perInstance
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roles.server.interface =
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{ lib, ... }:
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{
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options = lib.mkOption {
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type = lib.types.str;
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default = "/var/lib/borgbackup";
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description = ''
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The directory where the borgbackup repositories are stored.
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'';
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};
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};
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roles.server.perInstance =
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{
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instanceName,
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settings,
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roles,
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...
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}:
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{
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nixosModule =
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{ config, lib, ... }:
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let
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dir = config.clan.core.settings.directory;
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machineDir = dir + "/vars/per-machine/";
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allClients = roles.client.machines;
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in
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{
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# services.borgbackup is a native nixos option
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config.services.borgbackup.repos =
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let
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borgbackupIpMachinePath = machine: machineDir + machine + "/borgbackup/borgbackup.ssh.pub/value";
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machinesMaybeKey = builtins.map (
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machine:
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let
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fullPath = borgbackupIpMachinePath machine;
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in
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if builtins.pathExists fullPath then
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machine
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else
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lib.warn ''
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Machine ${machine} does not have a borgbackup key at ${fullPath},
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run `clan var generate ${machine}` to generate it.
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'' null
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) allClients;
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machinesWithKey = lib.filter (x: x != null) machinesMaybeKey;
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hosts = builtins.map (machine: {
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name = instanceName + machine;
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value = {
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path = "${settings.directory}/${machine}";
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authorizedKeys = [ (builtins.readFile (borgbackupIpMachinePath machine)) ];
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};
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}) machinesWithKey;
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in
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if (builtins.listToAttrs hosts) != [ ] then builtins.listToAttrs hosts else { };
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};
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};
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roles.client.interface =
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{ lib, ... }:
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{
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# There might be a better interface now. This is just how clan borgbackup was configured in the 'old' way
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options.destinations = lib.mkOption {
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type = lib.types.attrsOf (
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lib.types.submodule (
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{ name, ... }:
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{
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options = {
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name = lib.mkOption {
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type = lib.types.strMatching "^[a-zA-Z0-9._-]+$";
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default = name;
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description = "the name of the backup job";
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};
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repo = lib.mkOption {
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type = lib.types.str;
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description = "the borgbackup repository to backup to";
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};
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rsh = lib.mkOption {
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type = lib.types.nullOr lib.types.str;
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default = null;
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defaultText = "ssh -i \${config.clan.core.vars.generators.borgbackup.files.\"borgbackup.ssh\".path} -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null";
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description = "the rsh to use for the backup";
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};
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};
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}
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)
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);
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default = { };
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description = ''
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destinations where the machine should be backed up to
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'';
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};
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options.exclude = lib.mkOption {
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type = lib.types.listOf lib.types.str;
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example = [ "*.pyc" ];
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default = [ ];
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description = ''
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Directories/Files to exclude from the backup.
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Use * as a wildcard.
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'';
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};
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};
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roles.client.perInstance =
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{
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instanceName,
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roles,
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machine,
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settings,
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...
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}:
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{
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nixosModule =
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{
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config,
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lib,
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pkgs,
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...
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}:
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let
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allServers = roles.server.machines;
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# machineName = config.clan.core.settings.machine.name;
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# cfg = config.clan.borgbackup;
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preBackupScript = ''
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declare -A preCommandErrors
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${lib.concatMapStringsSep "\n" (
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state:
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lib.optionalString (state.preBackupCommand != null) ''
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echo "Running pre-backup command for ${state.name}"
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if ! /run/current-system/sw/bin/${state.preBackupCommand}; then
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preCommandErrors["${state.name}"]=1
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fi
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''
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) (lib.attrValues config.clan.core.state)}
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if [[ ''${#preCommandErrors[@]} -gt 0 ]]; then
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echo "pre-backup commands failed for the following services:"
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for state in "''${!preCommandErrors[@]}"; do
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echo " $state"
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done
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exit 1
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fi
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'';
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destinations =
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let
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destList = builtins.map (serverName: {
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name = "${instanceName}-${serverName}";
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value = {
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repo = "borg@${serverName}:/var/lib/borgbackup/${machine.name}";
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rsh = "ssh -i ${
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config.clan.core.vars.generators."borgbackup-${instanceName}".files."borgbackup.ssh".path
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} -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o IdentitiesOnly=Yes";
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} // settings.destinations.${serverName};
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}) allServers;
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in
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(builtins.listToAttrs destList);
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in
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{
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config = {
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# Derived from the destinations
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systemd.services = lib.mapAttrs' (
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_: dest:
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lib.nameValuePair "borgbackup-job-${instanceName}-${dest.name}" {
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# since borgbackup mounts the system read-only, we need to run in a ExecStartPre script, so we can generate additional files.
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serviceConfig.ExecStartPre = [
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''+${pkgs.writeShellScript "borgbackup-job-${dest.name}-pre-backup-commands" preBackupScript}''
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];
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}
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) destinations;
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services.borgbackup.jobs = lib.mapAttrs (_destinationName: dest: {
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paths = lib.unique (
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lib.flatten (map (state: state.folders) (lib.attrValues config.clan.core.state))
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);
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exclude = settings.exclude;
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repo = dest.repo;
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environment.BORG_RSH = dest.rsh;
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compression = "auto,zstd";
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startAt = "*-*-* 01:00:00";
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persistentTimer = true;
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encryption = {
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mode = "repokey";
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passCommand = "cat ${config.clan.core.vars.generators."borgbackup-${instanceName}".files."borgbackup.repokey".path}";
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};
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prune.keep = {
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within = "1d"; # Keep all archives from the last day
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daily = 7;
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weekly = 4;
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monthly = 0;
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};
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}) destinations;
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environment.systemPackages = [
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(pkgs.writeShellApplication {
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name = "borgbackup-create";
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runtimeInputs = [ config.systemd.package ];
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text = ''
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${lib.concatMapStringsSep "\n" (dest: ''
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systemctl start borgbackup-job-${dest.name}
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'') (lib.attrValues destinations)}
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'';
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})
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(pkgs.writeShellApplication {
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name = "borgbackup-list";
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runtimeInputs = [ pkgs.jq ];
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text = ''
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(${
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lib.concatMapStringsSep "\n" (
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dest:
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# we need yes here to skip the changed url verification
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''echo y | /run/current-system/sw/bin/borg-job-${dest.name} list --json | jq '[.archives[] | {"name": ("${dest.name}::${dest.repo}::" + .name)}]' ''
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) (lib.attrValues destinations)
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}) | jq -s 'add // []'
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'';
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})
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(pkgs.writeShellApplication {
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name = "borgbackup-restore";
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runtimeInputs = [ pkgs.gawk ];
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text = ''
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cd /
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IFS=':' read -ra FOLDER <<< "''${FOLDERS-}"
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job_name=$(echo "$NAME" | awk -F'::' '{print $1}')
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backup_name=''${NAME#"$job_name"::}
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if [[ ! -x /run/current-system/sw/bin/borg-job-"$job_name" ]]; then
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echo "borg-job-$job_name not found: Backup name is invalid" >&2
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exit 1
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fi
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echo y | /run/current-system/sw/bin/borg-job-"$job_name" extract "$backup_name" "''${FOLDER[@]}"
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'';
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})
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];
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# every borgbackup instance adds its own vars
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clan.core.vars.generators."borgbackup-${instanceName}" = {
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files."borgbackup.ssh.pub".secret = false;
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files."borgbackup.ssh" = { };
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files."borgbackup.repokey" = { };
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migrateFact = "borgbackup";
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runtimeInputs = [
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pkgs.coreutils
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pkgs.openssh
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pkgs.xkcdpass
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];
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script = ''
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ssh-keygen -t ed25519 -N "" -f $out/borgbackup.ssh
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xkcdpass -n 4 -d - > $out/borgbackup.repokey
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'';
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};
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};
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};
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};
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perMachine = {
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nixosModule =
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{ ... }:
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{
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clan.core.backups.providers.borgbackup = {
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list = "borgbackup-list";
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create = "borgbackup-create";
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restore = "borgbackup-restore";
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};
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};
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};
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}
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```
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## Prior-art
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- https://github.com/NixOS/nixops
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- https://github.com/infinisil/nixus
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