How to mount a host directory in a Docker container

Question

I am trying to mount a host directory into a Docker container so that any updates done on the host is reflected into the Docker containers.

Where am I doing somethin

Answer 1

How do I link the main_folder to the test_container folder present inside the docker container?

Your command below is correct, unless your on a mac using boot2docker(depending on future updates) in which case you may find the folder empty. See mattes answer for a tutorial on correcting this.

docker run -d -v /Users/kishore/main_folder:/test_container k3_s3:latest

I need to make this run automatically, how to do that without really using the run -d -v command.

You can't really get away from using these commands, they are intrinsic to the way docker works. You would be best off putting them into a shell script to save you writing them out repeatedly.

What happens if boot2docker crashes? Where are the docker files stored?

If you manage to use the -v arg and reference your host machine then the files will be safe on your host.

If you've used 'docker build -t myimage .' with a Dockerfile then your files will be baked into the image.

Your docker images, i believe, are stored in the boot2docker-vm. I found this out when my images disappeared when i delete the vm from VirtualBox. (Note, i don't know how Virtualbox works, so the images might be still hidden somewhere else, just not visible to docker).