create reproducable tar files

backupdb2/cli.py

@@ -135,6 +135,7 @@ def cmd_backup(args, parser, config, client):
 
     args_tar += ['nice', '-n', '19']
     args_tar += [get_tarcmd(),
+                 '--sort=name',
                  f'--exclude={LOCKFILE}',
                  '--warning=no-file-changed',
                  '--warning=no-file-removed',
@@ -143,9 +144,9 @@ def cmd_backup(args, parser, config, client):
 
     # Use pigz if available (Parallel gzip - http://zlib.net/pigz/)
     if has_binary("pigz"):
-        args_tar += ["--use-compress-program", "pigz"]
+        args_tar += ["--use-compress-program", "pigz -n"]
     else:
-        args_tar += ["-z"]
+        args_tar += ["--use-compress-program", "gzip -n"]  # pass -n to gzip to produce reproducible archives
 
     # Excluded paths
     if backup_config["exclude"]: