3 files changed, 384 insertions, 0 deletions

diff --git a/modules/borgbackup/btrfs-snapshots.nix b/modules/borgbackup/btrfs-snapshots.nix
new file mode 100644
index 00000000..96d2b2ba
--- /dev/null
+++ b/modules/borgbackup/btrfs-snapshots.nix
@@ -0,0 +1,52 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.btrfs-snapshots;
+
+  snapshotMount = str: "${str}${cfg.mountSuffix}";
+in {
+  options = {
+
+    services.btrfs-snapshots = {
+      enable = mkEnableOption "a systemd unit for btrfs snapshots";   
+
+      mountSuffix = mkOption {
+        type = types.str;
+        default = ".snapshot";
+      };
+
+      readOnly = mkOption {
+        type = types.bool;
+        default = true;
+      };
+
+      persist = mkOption {
+        type = types.bool;
+        default = false;
+      };
+    };
+
+  };
+
+  
+  config = mkIf cfg.enable {
+    systemd.services."btrfs-snapshot@" = {
+      enable = true;
+
+      unitConfig = {
+        StopWhenUnneeded = !cfg.persist;
+      };
+
+      serviceConfig = with pkgs; {
+        Type = "oneshot";
+        ExecStartPre = "-${btrfs-progs}/bin/btrfs subvolume delete -c ${snapshotMount "%f"}";
+        ExecStart = "${btrfs-progs}/bin/btrfs subvolume snapshot ${optionalString cfg.readOnly "-r"} %f ${snapshotMount "%f"}";
+        RemainAfterExit = true;
+        ExecStop = "${btrfs-progs}/bin/btrfs subvolume delete -c ${snapshotMount "%f"}";
+      };
+    };
+
+  };
+}
diff --git a/modules/borgbackup/default.nix b/modules/borgbackup/default.nix
new file mode 100644
index 00000000..47f8e06d
--- /dev/null
+++ b/modules/borgbackup/default.nix
@@ -0,0 +1,199 @@
+{ config, lib, utils, pkgs, ... }:
+
+with utils;
+with lib;
+
+let
+  cfg = config.services.borgbackup;
+
+  lvmPath = {
+    options = {
+      LV = mkOption {
+        type = types.str;
+      };
+      VG = mkOption {
+        type = types.str;
+      };
+    };
+  };
+
+  pathType = if cfg.snapshots == "lvm" then types.submodule lvmPath else types.path;
+
+  systemdPath = path: escapeSystemdPath (if cfg.snapshots == "lvm" then "${path.VG}-${path.LV}" else path);
+
+  withSuffix = path: path + (if cfg.snapshots == "btrfs" then config.services.btrfs-snapshots.mountSuffix else config.services.lvm-snapshots.mountSuffix);
+
+  mountPoint = if cfg.snapshots == "lvm" then config.services.lvm-snapshots.mountPoint else "";
+
+  targetOptions = {
+    options = {
+      repo = mkOption {
+        type = types.str;
+      };
+    
+      paths = mkOption {
+        type = types.listOf pathType;
+        default = [];
+      };
+
+      prune = mkOption {
+        type = types.attrsOf (types.listOf types.str);
+        default = {};
+      };
+
+      interval = mkOption {
+        type = types.str;
+        default = "6h";
+      };
+
+      jitter = mkOption {
+        type = with types; nullOr str;
+        default = "6h";
+      };
+
+      lock = mkOption {
+        type = types.nullOr types.str;
+        default = "backup";
+      };
+
+      network = mkOption {
+        type = types.bool;
+        default = true;
+      };
+
+      lockWait = mkOption {
+        type = types.int;
+        default = 600;
+      };
+    };
+  };
+in {
+  disabledModules = [ "services/backup/borgbackup.nix" ];
+  
+  options = {
+    services.borgbackup = {
+      snapshots = mkOption {
+        type = types.nullOr (types.enum ["btrfs" "lvm"]);
+        default = null;
+      };
+
+      targets = mkOption {
+        type = types.attrsOf (types.submodule targetOptions);
+        default = {};
+      };
+
+      prefix = mkOption {
+        type = types.str;
+      };
+    };
+  };
+
+  imports =
+    [ ./lvm-snapshots.nix
+      ./btrfs-snapshots.nix
+    ];
+
+  config = mkIf (any (t: t.paths != []) (attrValues cfg.targets)) {
+    services.btrfs-snapshots.enable = mkIf (cfg.snapshots == "btrfs") true;
+
+    services.lvm-snapshots.snapshots = mkIf (cfg.snapshots == "lvm") (listToAttrs (map (path: nameValuePair (path.VG + "-" + path.LV) {
+      inherit (path) LV VG; 
+      mountName = withSuffix (path.VG + "-" + path.LV);
+    }) (unique (flatten (mapAttrsToList (target: tCfg: tCfg.paths) cfg.targets)))));
+
+    systemd.targets."timers-borg" = {
+      wantedBy = [ "timers.target" ];
+    };
+
+    systemd.slices."system-borgbackup" = {};
+  
+    systemd.timers = (listToAttrs (map ({ target, path, tCfg }: nameValuePair "borgbackup-${target}@${systemdPath path}" {
+      requiredBy = [ "timers-borg.target" ];
+
+      timerConfig = {
+        Persistent = false;
+        OnBootSec = tCfg.interval;
+        OnUnitActiveSec = tCfg.interval;
+        RandomizedDelaySec = mkIf (tCfg.jitter != null) tCfg.jitter;
+      };
+    }) (flatten (mapAttrsToList (target: tCfg: map (path: { inherit target path tCfg; }) tCfg.paths) cfg.targets)))) // (mapAttrs' (target: tCfg: nameValuePair "borgbackup-prune-${target}" {
+      enable = tCfg.prune != {};
+    
+      requiredBy = [ "timers-borg.target" ];
+
+      timerConfig = {
+        Persistent = false;
+        OnBootSec = tCfg.interval;
+        OnUnitActiveSec = tCfg.interval;
+        RandomizedDelaySec = mkIf (tCfg.jitter != null) tCfg.jitter;
+      };
+    }) cfg.targets);
+
+    systemd.services = (mapAttrs' (target: tCfg: nameValuePair "borgbackup-${target}@" (let
+      deps = flatten [
+        (optional (cfg.snapshots == "btrfs") "btrfs-snapshot@%i.service")
+        (optional tCfg.network "network-online.target")
+      ];
+    in {
+      bindsTo = deps;
+      after = deps;
+
+      path = with pkgs; [borgbackup] ++ optional (tCfg.lock != null) utillinux;
+
+      script = let
+        borgCmd = ''
+          borg create \
+            --lock-wait ${toString tCfg.lockWait} \
+            --stats \
+            --list \
+            --filter 'AME' \
+            --exclude-caches \
+            --keep-exclude-tags \
+            --patterns-from .backup-${target} \
+            --one-file-system \
+            --compression auto,lzma \
+            ${tCfg.repo}::${cfg.prefix}$1-{utcnow}
+        '';
+      in if tCfg.lock == null then borgCmd else "flock -xo /var/lock/${tCfg.lock} ${borgCmd}";
+      scriptArgs = if cfg.snapshots == "lvm" then "%I" else "%i";
+
+      unitConfig = {
+        AssertPathIsDirectory = mkIf (tCfg.lock != null) "/var/lock";
+        DefaultDependencies = false;
+        RequiresMountsFor = mkIf (cfg.snapshots == "lvm") [ "${mountPoint}/${withSuffix "%I"}" ];
+      };
+
+      serviceConfig = {
+        Type = "oneshot";
+        WorkingDirectory = if (cfg.snapshots == null) then "%I" else (if (cfg.snapshots == "lvm") then "${mountPoint}/${withSuffix "%I"}" else "${withSuffix "%f"}");
+        Nice = 15;
+        IOSchedulingClass = 2;
+        IOSchedulingPriority = 7;
+        SuccessExitStatus = [1 2];
+        Slice = "system-borgbackup.slice";
+      };
+    })) cfg.targets) // (mapAttrs' (target: tCfg: nameValuePair "borgbackup-prune-${target}" {
+      enable = tCfg.prune != {};
+    
+      bindsTo = ["network-online.target"];
+      after = ["network-online.target"];
+
+      path = with pkgs; [borgbackup];
+
+      script = concatStringsSep "\n" (mapAttrsToList (path: args: ''
+        borg prune \
+          --lock-wait ${toString tCfg.lockWait} \
+          --list \
+          --stats \
+          --prefix ${escapeShellArg "${cfg.prefix}${path}"} \
+          ${escapeShellArgs args} \
+          ${tCfg.repo}
+      '') tCfg.prune);
+
+      serviceConfig = {
+        Type = "oneshot";
+        Slice = "system-borgbackup.slice";
+      };
+    }) cfg.targets);
+  };
+}
diff --git a/modules/borgbackup/lvm-snapshots.nix b/modules/borgbackup/lvm-snapshots.nix
new file mode 100644
index 00000000..9b2a6562
--- /dev/null
+++ b/modules/borgbackup/lvm-snapshots.nix
@@ -0,0 +1,133 @@
+{ config, lib, utils, pkgs, ... }:
+
+with utils;
+with lib;
+
+let
+  cfg = config.services.lvm-snapshots;
+
+  snapshotMount = name: "${cfg.mountPoint}/${if isNull cfg.snapshots."${name}".mountName then name else cfg.snapshots."${name}".mountName}";
+  snapshotName = name: "${name}-${cfg.mountSuffix}";
+
+  snapshotConfig = {
+    options = {
+      LV = mkOption {
+        type = types.str;
+      };
+
+      VG = mkOption {
+        type = types.str;
+      };
+
+      mountName = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+      };
+      
+      cowSize = mkOption {
+        type = types.str;
+        default = "-l20%ORIGIN";
+      };
+
+      readOnly = mkOption {
+        type = types.bool;
+        default = true;
+      };
+
+      persist = mkOption {
+        type = types.bool;
+        default = false;
+      };
+    };
+  };
+in {
+  options = {
+
+    services.lvm-snapshots = {
+      snapshots = mkOption {
+        type = types.attrsOf (types.submodule snapshotConfig);
+        default = {};
+      };
+
+      mountPoint = mkOption {
+        type = types.path;
+        default = "/mnt";
+      };
+
+      mountSuffix = mkOption {
+        type = types.str;
+        default = "-snapshot";
+      };
+    };
+  };
+
+  
+  config = mkIf (cfg != {}) {
+
+    boot.kernelModules = [ "dm_snapshot" ];
+
+    # system.activationScripts = mapAttrs' (name: scfg: nameValuePair ("lvm-mountpoint" + name) ''
+    #   mkdir -p ${snapshotMount name}
+    # '') cfg.snapshots;
+
+    systemd.services = mapAttrs' (name: scfg: nameValuePair ("lvm-snapshot@" + escapeSystemdPath name) {
+      enable = true;
+
+      description = "LVM-snapshot of ${scfg.VG}/${scfg.LV}";
+
+      bindsTo = ["${escapeSystemdPath "/dev/${scfg.VG}/${scfg.LV}"}.device"];
+      after = ["${escapeSystemdPath "/dev/${scfg.VG}/${scfg.LV}"}.device"];
+
+      unitConfig = {
+        StopWhenUnneeded = !scfg.persist;
+        AssertPathIsDirectory = "/var/lock";
+      };
+
+      path = with pkgs; [ devicemapper utillinux ];
+      
+      script = ''
+        (
+          flock -xn -E 4 9
+          if [[ "$?" -ne 0 ]]; then
+            exit $?
+          fi
+          
+          lvcreate -s ${scfg.cowSize} --name ${snapshotName name} ${scfg.VG}/${scfg.LV}
+
+          sleep infinity &
+        ) 9>/var/lock/lvm-snapshot.${scfg.VG}
+      '';
+      
+      preStart = ''
+        lvremove -f ${scfg.VG}/${snapshotName name}
+      '';
+
+      preStop = ''
+        lvremove -f ${scfg.VG}/${snapshotName name}
+      '';
+
+      serviceConfig = with pkgs; {
+        Type = "forking";
+        RestartForceExitStatus = [ "4" ];
+        RestartSec = "5min";
+      };
+    }) cfg.snapshots;
+
+    systemd.mounts = mapAttrsToList (name: scfg: {
+      enable = true;
+
+      unitConfig = {
+        # AssertPathIsDirectory = snapshotMount name;
+        StopWhenUnneeded = !scfg.persist;
+      };
+
+      bindsTo = [ ("lvm-snapshot@" + escapeSystemdPath name + ".service") ];
+      after = [ ("lvm-snapshot@" + escapeSystemdPath name + ".service") ];
+
+      options = concatStringsSep "," ([ "noauto" ] ++ optional scfg.readOnly "ro");
+
+      where = snapshotMount name;
+      what = "/dev/" + scfg.VG + "/" + snapshotName name;
+    }) cfg.snapshots;
+  };
+}