Fix doc and reduce image size

Fix paritytech#375

README.md

@@ -2,15 +2,36 @@
 
 Implementation of a https://polkadot.network node in Rust.
 
-## Press start
+## Using Docker
 
-To get up and running with the smallest footprint on your system, you may use the Polkadot Docker image.
-You can either build it yourself or use the latest published one:
+### The easiest way
+
+The easiest/faster option is to use the latest image.
+
+Let´s first check the version we have. The first time you run this command, the polkadot docker image will be downloaded. This takes a bit of time and bandwidth, be patient:
+
+```
+docker run --rm -it polkadot:0.2.0 polkadot --version
+```
+
+You can also pass any argument/flag that polkadot supports:
 
 ```
-docker run --rm -it polkadot:0.2.0 /polkadot/target/debug/polkadot --name "PolkaDocker"
+docker run --rm -it polkadot:0.2.0 polkadot --name "PolkaDocker"
 ```
 
+Once you are done experimenting and picking the best node name :) you can start polkadot as daemon, exposes the polkadot ports and mount a volume that will keep your blockchain data locally:
+
+```
+docker run -d -p 30333:30333 -p 9933:9933 -v /my/local/folder:/root/.local/share/Polkadot polkadot:0.2.0 polkadot
+```
+
+
+### Build your own image
+To get up and running with the smallest footprint on your system, you may use the Polkadot Docker image.
+You can either build it yourself (it takes a while...):
+
+
 ## To play
 
 If you'd like to play with Polkadot, you'll need to install a client like this

docker/Dockerfile

@@ -20,6 +20,7 @@ RUN curl https://sh.rustup.rs -sSf | sh -s -- -y && \
 	cargo build --$PROFILE && \
 	cp target/$PROFILE/polkadot /usr/local/bin && \
 	cargo clean && \
+	rm -rf /root/.cargo /root/.rustup
 
 WORKDIR /polkadot
 EXPOSE 30333 9933

docker/build.sh

@@ -4,7 +4,7 @@ set -e
 VERSION=`grep "^version" ../Cargo.toml | egrep -o "([0-9\.]+)"`
 
 echo "Building polkadot:$VERSION docker image, hang on!"
-docker build --build-arg PROFILE=release -t polkadot:$VERSION .
+time docker build --build-arg PROFILE=release -t polkadot:$VERSION .
 
 echo "Image is ready"
 docker images | grep polkadot