add doc

scripts/docker/staking_miner-injected.Dockerfile

@@ -1,8 +1,3 @@
-# to build on a linux host:
-#   cargo build --release --lockec -p staking-miner
-#   cd target/release
-# 	docker build -t taking-miner -f ../../scripts/docker/staking_miner-injected.Dockerfile .
-
 FROM debian:buster-slim
 
 # metadata
@@ -30,13 +25,12 @@ ENV RUST_BACKTRACE 1
 RUN apt-get update && \
 	DEBIAN_FRONTEND=noninteractive apt-get install -y \
 		libssl1.1 \
-		ca-certificates \
-		curl && \
+		ca-certificates && \
 # apt cleanup
 	apt-get autoremove -y && \
 	apt-get clean && \
 	find /var/lib/apt/lists/ -type f -not -name lock -delete; \
-	useradd -m -u 1000 -U -s /bin/sh -d /polkadot polkadot
+	useradd -m -u 1000 -U -s /bin/sh
 	# && \
 	# mkdir -p /data /polkadot/.local/share && \
 	# chown -R polkadot:polkadot /data && \

utils/staking-miner/README.md

@@ -0,0 +1,55 @@
+# Staking Miner
+
+The staking miner connects to a specified chains and keeps
+listening to new Phragmen elections. When the time comes,
+it computes its solution and submit it to the chain. Running
+the staking-miner requires passing the seed of a funded
+account in order to pay the fees for the transactions that
+will be sent. At the moment, submitting solutions is not
+rewarded.
+
+You can check the help with:
+```
+staking-miner --help
+```
+
+## Building
+
+You can build from the root of the Polkadot repository using:
+```
+cargo build --release --locked --package staking-miner
+```
+
+## Docker
+
+### Building
+
+You can also use docker on a Linux host from the root of the Polkadot repository after building the binary (see above):
+```
+docker build -t staking-miner -f scripts/docker/staking_miner-injected.Dockerfile target/release
+```
+
+### Running
+
+A Docker container, especially one holding one of your `SEED` should be kept secure. It is recommended running this container in `read-only` mode:
+
+```
+docker run --rm -it \
+    --name staking-miner \
+    --read-only \
+    -v /tmp/seed.txt:/seed.txt \
+    staking-miner \
+        --account-seed /seed.txt \
+        --uri wss://your-nodes:9944 \
+        dry-run
+```
+
+There is a [pending PR](https://github.com/paritytech/polkadot/pull/3680) that removes the need to pass the seed as a file. The commend will then become:
+```
+docker run --rm -it \
+    --name staking-miner \
+    --read-only \
+    -e SEED=0x1234... \
+    -e URI=wss://your-nodes:9944 \
+    staking-miner dry-run
+```