RickyCook/Command.md

## Command.md

      
    Raw
  

              Command.md
            
          
    What?... Why?

Imagine you're messing around in a container, and you install some stuff, add
some config, and now it's time to load up your client and check it out! Oh wait,
you forgot to forward ports when you created the container! Fear not, all is
not lost, for in the world of pipes, and streams, there is always a way to do
something disgusting.
The Dockerfile

Example Dockerfile included will install Nginx, and socat in a container, and
make Nginx run in foreground mode. To build, and run:
docker build .
docker run -it --name socat-nginx <image_id>

This will give you a container running Nginx on port 80, but with no forwarded ports.
The awful socat one-liner

I'll just get right into it. Forgive me:
socat TCP-LISTEN:8080,reuseaddr,fork 'EXEC:docker exec -i socat-nginx "socat STDIO TCP-CONNECT:localhost:80"'

So what's this doing?

TCP-LISTEN:8080: socat running locally will accept connections of port 8080
reuseaddr,fork: When accepting a connection, socat will fork to handle it. This
means that it can handle parallel connections, and won't die after the first connection
EXEC:...: Instructs socat to execute a command, and forward the accepted
connection (in this case, our TCP-LISTEN) to the standard input/output. This will
happen every time socat accepts a connection
docker exec -i socat-nginx: Execute a new command in our running container. -i
lets Docker know that we want to immediately attach (formard stardard in/out/err)
socat STDIO: In the Docker container, run socat and accept standard input/output as
the stream source
TCP-CONNECT:localhost:80: Open a connection to port 80 in the container, and stream
stdin to it's write buffer. Socat will read, and stream from the port to stdout (which
is passed back through Docker, to local socat, and out the TCP port we've given)


## Dockerfile
FROM alpine:3.2

RUN apk add --update nginx socat && \
    rm -rf /var/cache/apk/*
RUN echo 'daemon off;' >> /etc/nginx/nginx.conf
CMD ["/usr/sbin/nginx"]
	FROM alpine:3.2

	RUN apk add --update nginx socat && \
	rm -rf /var/cache/apk/*
	RUN echo 'daemon off;' >> /etc/nginx/nginx.conf
	CMD ["/usr/sbin/nginx"]