prepare README (quick start & tips)

README.md

@@ -1,2 +1,68 @@
 # docker-nerves
 Docker image for Nerves development
+
+## Quick start
+
+```Shell
+$ git clone https://github.com/NervesJP/docker-nerves
+$ cd docker-nerves
+
+$ docker build -t docker-nerves .
+$ docker run -it -w /workspace docker-nerves 
+root@9bc88d0fc7b8:/workspace# pwd
+/workspace
+root@9bc88d0fc7b8:/workspace# echo ${HOME}
+/root
+root@9bc88d0fc7b8:/workspace# ls ~/.mix/*
+/root/.mix/rebar  /root/.mix/rebar3
+
+/root/.mix/archives:
+hex-0.20.6  nerves_bootstrap-1.10.0
+```
+
+## Expected tools/versions to be installed
+
+### v0.1
+
+- Debian 10.6
+- Erlang/OTP 23.1.3
+- Elixir 1.11.2-otp-23
+- Nerves 1.7.0
+    - hex 0.20.6
+    - rebar 2.6.4 / 3.14.2
+    - nerves_bootstrap 1.10.0
+- fwup 1.8.2
+
+## Tips
+
+### Mount volumes on host
+
+Since a filesystem into Docker image will disappear when an image rebuild/execute, it is useful to mount a volume on host to keep files of Nerves project. `-v ${PWD}:/workspace` can mount current directory on host to Docker image.
+
+```Shell
+$ docker run -it -w /workspace -v ${PWD}:/workspace docker-nerves 
+```
+
+It is also efficient to mount Nerves related setting files, such as `~/.ssh/` and `~/.nerves`. Following is an example to share setting files between host and image.
+
+```Shell
+$ docker run -it -w /workspace -v ${PWD}:/workspace  -v ~/.ssh:/root/.ssh -v ~/.nerves:/root/.nerves docker-nerves 
+```
+
+## Current limitation(s)
+
+### burn Nerves firmware to microSD card
+
+Docker has restrict policies to avoid effecting host environment. Therefore, `mix burn` cannot be operated from Docker image because there is no right to access `/dev` to on host as a root user.
+
+One way to burn Nerves firmware is just operating `fwup` on the host. `fwup` is an utility for constructing/burning Nerves firmware.  
+https://github.com/fhunleth/fwup
+
+After installing `fwup` on the host according to [this step](https://github.com/fhunleth/fwup#installing), please do following command on the host terminal.
+
+```Shell
+$ cd <your_nerves_project_dir>
+$ fwup _build/${MIX_TARGET}_dev/nerves/images/<project_name>.fw
+```
+
+Please let us know if you have a cool solution!