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Notes on Docker

Concepts

  • "A Docker image is an executable package that includes everything needed to run an application---the code, a runtime, libraries, environment variables, and config files"
  • A container is a runtime instance of an image (an image with state or a user process). Use docker ps to see a list of running containers
  • "containers runs natively on Linux and shares the kernel of the host machine with other containers"
  • A virtual machine on the other hand runs a full-blown guest operating system with virtual access to the host computer's resources through a hypervisor. VMs demand more resource than what is needed by a given application that can be run in a container.
  • See https://docs.docker.com/get-started/ for more details

Getting Started

Build

  • Build an image from Dockerfile in current dir and tag the image
# Uses Dockerfile by default
docker build -t myimage:1.0 .

# Use Dockerfile.local to build image
docker build -f Dockerfile.local -t myimage:1.0 .
  • List all images locally stored images
docker image ls

Run

  • Run built image
docker run -t myimage
  • Run bash in a container in interactive mode Say you have the myimage image (check with docker image). To access bash in its container in interactive mode, run
docker run -i -t myimage bash
  • List all running containers
docker container ls

Housekeeping (cleaning up images and containers)

  • Delete image from local image store
docker image rm myimage:1.0
  • Remove all stopped containers and all unused images and build cache
docker system prune -a

Useful Docker commands

  1. List active docker containers: docker ps

  2. Open multiple terminals on a docker container: docker exec -it <container name> bash

    • You can get container name from docker ps

  3. How to get access to data in the host from inside a container

    • docker run -it -v /path/in/host:/path/in/container <docker image name>
      • This gives access to the data in the host (found in /Users/s6215054/Desktop/courses/python-spark-datascience), which can be found in /home/jovyan/work in the container

  4. How to set own name for docker container

    • docker run --name <MY_CUSTOM_NAME> <DOCKER_IMAGE>

  5. How to exit docker container in interactive mode

    • Just type exit

  6. Delete image by image id: docker rmi <IMAGE ID>

  7. Kill an active container: docker kill <CONTAINER ID>

Dockerfile

See docker_fun repository for an example using a Ubuntu base image

Additional Notes and Features

  • the -it options run docker in interactive mode (i.e. it takes you inside and container and do stuff in it). Alternatively, you can run it in detached mode by using the -d option