Allow container list override in main pipeline

README.md

@@ -113,6 +113,16 @@ Preview all stages without stopping containers, copying, or deleting:
 sudo /backupdockerscripts/backup.sh --dry-run
 ```
 
+Select a different container list for one complete pipeline run:
+
+```bash
+sudo /backupdockerscripts/backup.sh --containers containers-special.txt
+```
+
+Relative container-list paths are resolved from the repository directory;
+absolute paths are also accepted. The selected list affects only the container
+archive stage, after which configured transfer methods and pruning continue.
+
 Run individual parts:
 
 ```bash