Update README.md

README.md

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 # clean_registry
-Clean the Docker Registry by removing untagged repositories. The optional flag -x may be used to remove repositories or tagged images
+Clean the Docker Registry by removing untagged repositories and running the garbage collector in Docker Registry >= 2.4.0
+
+The optional `-x` flag may be used to remove the specified repositories or tagged images.
+
+NOTES:
+  - This script stops the Registry container during cleanup to prevent corruption, making it temporarily unavailable to clients.
+  - This script assumes local storage (the filesystem storage driver).
+  - This script may run standalone or dockerized.  To run standalone, you must install **docker-py** with `pip3 install docker` and **pyyaml** with `pip3 install pyyaml`.
+  - This script is Python 3 only.
+  
+## Usage:
+
+```
+clean_registry.py [OPTIONS] CONTAINER [REPOSITORY[:TAG]]...`
+Options:
+        -x, --remove    Remove the specified images or repositories.
+        -q, --quiet     Supress non-error messages.
+        -V, --version   Show version and exit.
+```
+
+## Docker usage:
+
+`docker run --rm --volumes-from CONTAINER ricardobranco/clean_registry [OPTIONS] CONTAINER [REPOSITORY[:TAG]]...`