btrbk_restore_raw.py: add dry-run mode

contrib/tools/btrbk_restore_raw.py

@@ -11,6 +11,9 @@ logger = logging.getLogger(__name__)
 
 class TransformProcess:
     def run(self, bfile, options, **kw):
+        return subprocess.Popen(self.get_cmd(bfile, options), **kw)
+
+    def get_cmd(self, bfile, options):
         raise NotImplementedError()
 
     @classmethod
@@ -20,13 +23,14 @@ class TransformProcess:
 
 class TransformOpensslDecrypt(TransformProcess):
     @staticmethod
-    def run(bfile, options, **kw):
-        return subprocess.Popen([
+    def get_cmd(bfile, options):
+        return [
             'openssl', 'enc', '-d', '-' + bfile.info['cipher'], '-K',
-            open(options.openssl_keyfile, 'r').read(), '-iv', bfile.info['iv']], **kw)
+            open(options.openssl_keyfile, 'r').read(), '-iv', bfile.info['iv']
+        ]
 
-    @classmethod
-    def add_parser_options(cls, parser):
+    @staticmethod
+    def add_parser_options(parser):
         parser.add_argument('--openssl-keyfile', help="path to private encryption key file")
 
 
@@ -34,14 +38,18 @@ class TransformDecompress(TransformProcess):
     def __init__(self, program):
         self.p = program
 
-    def run(self, bfile, options, **kw):
-        return subprocess.Popen([self.p, '-d'], **kw)
+    def get_cmd(self, bfile, options):
+        return [self.p, '-d']
 
 
 class TransformBtrfsReceive(TransformProcess):
+    @classmethod
+    def run(cls, bfile, options, **kw):
+        return subprocess.Popen(cls.get_cmd(bfile, options), **kw)
+
     @staticmethod
-    def run(bfile, options, **kw):
-        return subprocess.Popen(['btrfs', 'receive', options.restore_dir], **kw)
+    def get_cmd(bfile, options):
+        return ['btrfs', 'receive', options.restore_dir]
 
 
 TRANSFORMERS = (
@@ -96,6 +104,13 @@ class BtrfsPipeline:
                                 if msg:
                                     logger.error(f"error running {p.args}: {msg}")
 
+    def get_cmd(self, options):
+        command_pipe = [['cat', self.bfile.data_file]]
+        for transformer in self.processors:
+            command_pipe.append(transformer.get_cmd(self.bfile, options))
+        command_pipe.append(TransformBtrfsReceive.get_cmd(self.bfile, options))
+        return ' | '.join(' '.join(x) for x in command_pipe)
+
 
 class BackupFile:
     def __init__(self, path):
@@ -132,11 +147,14 @@ class BackupFile:
     def restore_file(self, options):
         assert self.info.get('TYPE') == 'raw'
         assert not self.info.get('INCOMPLETE')
-        logger.info(f"restoring backup {os.path.basename(self.data_file)}")
         pipeline = BtrfsPipeline(self)
         for transformer in self.get_transformers():
             pipeline.append(transformer)
-        pipeline.run(options)
+        if options.dry_run:
+            print(pipeline.get_cmd(options))
+        else:
+            logger.info(f"restoring backup {os.path.basename(self.data_file)}")
+            pipeline.run(options)
         self.is_restored = True
 
 
@@ -175,13 +193,21 @@ def main():
     parser = argparse.ArgumentParser(description="restore btrbk raw backup")
     parser.add_argument('backup', help="backup file to restore; for incremental"
                         " backups the parent files must be in the same directory")
-    parser.add_argument('restore_dir', help="target directory for restored subvolumes (path argument for \"btrfs receive\")")
-    parser.add_argument('--ignore-missing', action='store_true', help="do not fail on missing parent snapshots")
+    parser.add_argument('restore_dir', help="target directory for restored subvolumes"
+                                            " (path argument for \"btrfs receive\")")
+    parser.add_argument('--ignore-missing', action='store_true',
+                        help="do not fail on missing parent snapshots")
+    parser.add_argument('--dry-run', '-n', action='store_true',
+                        help="print commmands that would be exectuted")
 
     for transformer in TRANSFORMERS:
         transformer.add_parser_options(parser)
 
     args = parser.parse_args()
+
+    if args.dry_run:
+        logger.setLevel('ERROR')
+
     restore_from_path(args.backup, args)