nixos/borgbackup: allow dump scripts as stdin inputs

borg is able to process stdin during backups when backing up the special path -,
which can be very useful for backing up things that can be streamed (eg database
dumps, zfs snapshots).

1 files changed, 35 insertions, 8 deletions

diff --git a/nixos/modules/services/backup/borgbackup.nix b/nixos/modules/services/backup/borgbackup.nix
index 5461dbaf0bd0..220c571b927e 100644
--- a/nixos/modules/services/backup/borgbackup.nix
+++ b/nixos/modules/services/backup/borgbackup.nix
@@ -42,12 +42,16 @@ let
       ${cfg.postInit}
     fi
   '' + ''
-    borg create $extraArgs \
-      --compression ${cfg.compression} \
-      --exclude-from ${mkExcludeFile cfg} \
-      $extraCreateArgs \
-      "::$archiveName$archiveSuffix" \
-      ${escapeShellArgs cfg.paths}
+    (
+      set -o pipefail
+      ${optionalString (cfg.dumpCommand != null) ''${escapeShellArg cfg.dumpCommand} | \''}
+      borg create $extraArgs \
+        --compression ${cfg.compression} \
+        --exclude-from ${mkExcludeFile cfg} \
+        $extraCreateArgs \
+        "::$archiveName$archiveSuffix" \
+        ${if cfg.paths == null then "-" else escapeShellArgs cfg.paths}
+    )
   '' + optionalString cfg.appendFailedSuffix ''
     borg rename $extraArgs \
       "::$archiveName$archiveSuffix" "$archiveName"
@@ -182,6 +186,14 @@ let
       + " without at least one public key";
   };
 
+  mkSourceAssertions = name: cfg: {
+    assertion = count isNull [ cfg.dumpCommand cfg.paths ] == 1;
+    message = ''
+      Exactly one of borgbackup.jobs.${name}.paths or borgbackup.jobs.${name}.dumpCommand
+      must be set.
+    '';
+  };
+
   mkRemovableDeviceAssertions = name: cfg: {
     assertion = !(isLocalPath cfg.repo) -> !cfg.removableDevice;
     message = ''
@@ -240,11 +252,25 @@ in {
         options = {
 
           paths = mkOption {
-            type = with types; coercedTo str lib.singleton (listOf str);
-            description = "Path(s) to back up.";
+            type = with types; nullOr (coercedTo str lib.singleton (listOf str));
+            default = null;
+            description = ''
+              Path(s) to back up.
+              Mutually exclusive with <option>dumpCommand</option>.
+            '';
             example = "/home/user";
           };
 
+          dumpCommand = mkOption {
+            type = with types; nullOr path;
+            default = null;
+            description = ''
+              Backup the stdout of this program instead of filesystem paths.
+              Mutually exclusive with <option>paths</option>.
+            '';
+            example = "/path/to/createZFSsend.sh";
+          };
+
           repo = mkOption {
             type = types.str;
             description = "Remote or local repository to back up to.";
@@ -657,6 +683,7 @@ in {
       assertions =
         mapAttrsToList mkPassAssertion jobs
         ++ mapAttrsToList mkKeysAssertion repos
+        ++ mapAttrsToList mkSourceAssertions jobs
         ++ mapAttrsToList mkRemovableDeviceAssertions jobs;
 
       system.activationScripts = mapAttrs' mkActivationScript jobs;