adding macOS support via Docker

.dockerignore

@@ -0,0 +1 @@
+*.img

Dockerfile

@@ -0,0 +1,3 @@
+FROM ubuntu:latest
+RUN apt-get update
+RUN apt-get install parted udev -y

README.md

@@ -74,6 +74,16 @@ The filesystem on /dev/loop1 is now 773603 blocks long.
 Shrunk pi.img from 30G to 3.1G
 ```
 
+## macOS Support ##
+
+It is not currently possible to run PiShrink natively in macOS. Included in the repo is a `Dockerfile` and `docker-compose.yml` that should allow you to run PiShrink on a Docker host, including a macOS one.
+
+Note 1: The cloned repo is mounted as a Docker host mount so any output file should be created under `/pishrink` to have it persisted on the host.
+
+Note 2: Only `*.img` is present in the provided `.dockerignore`, if you don't use this extension the created container will include your image, potentially consuming a significant amount of disk space. 
+
+Example: `docker-compose run pishrink /pishrink/pishrink.sh /pishrink/someimage.img`
+
 ## Contributing ##
 
 If you find a bug please create an issue for it. If you would like a new feature added, you can create an issue for it but I can't promise that I will get to it.

docker-compose.yml

@@ -0,0 +1,9 @@
+version: '2'
+
+services:
+  pishrink:
+    build: .
+    volumes:
+      - .:/pishrink
+      - /dev:/dev
+    privileged: true