Dicas interessantes para docker

Exposing a port on a live container

From this Stack Overflow hint:

1. Discover the IP of the machine:

   docker inspect container_name | grep -i IPAddress

2. Create an IPTables rule (with root permissions):

   iptables -t nat -A DOCKER -p tcp --dport 8001 -j DNAT --to-destination container-ip:8000

3. Now you can access the container contents through the hostsIP:port

Limpando o lixo deixado para trás

From this site:

Make sure that exited containers are deleted.

docker rm -v $(docker ps -a -q -f status=exited)

Remove unwanted ‘dangling’ images.

docker rmi $(docker images -f "dangling=true" -q)

Still not enough space? What is this ‘vfs’ directory?

docker run -v /var/run/docker.sock:/var/run/docker.sock -v /var/lib/docker:/var/lib/docker --rm martin/docker-cleanup-volumes

Acessing the container to use debugging tools

In rails development sometimes we have to use pry via binding.pry to debug our code.

As we need to be on the same terminal that is running the process we need to start our server manually:

docker-compose run --service-ports <container-name-defined-in-the-docker-compose-file> /bin/bash
rails s

And then, when we hit the breakpoint (binding.pry) we can use pry normally.

Checking environment variables on a live container

With the help of 1 and 2:

docker inspect --format '{{ range $index, $value := .Config.Env }}{{ println $value }}{{ end }}' <container_id>

Accessing a stopped container

With the help of 1 and 2:

docker commit STOPPED_CONTAINER NEW_IMAGE_NAME
docker run -ti NEW_IMAGE_NAME /bin/bash
# or
docker run -ti --entrypoint=/bin/sh NEW_IMAGE_NAME