heidikumar / dockernotes

Tips & Tricks for Docker

Docker Tips and Tricks

This file is a reference for some basic ideas and commands around Docker.

What are images and containers?

Docker images are read-only files that are layered one on top of the other. An image can pull a previous image using a ‘From’ statement. Multiple FROM statements can be used technically, but Docker doesn’t advise this. Layered images pull in all the environmental specifications you need for your container. Docker images are static.

Docker containers are a thin, writable layer on top of the image. You can interact with containers, change files around, write new information, etc in a container. An example is running a container off a Postgres image and then saving the info in the database. That data will persist as long as the container is running.

Image related commands

Build an image called "imageName" from Dockerfile in current folder: docker build -t imageName .

Look at history of an image: docker history {{ImageID#}}

Container related commands

Example of running an image of a server: docker run -it -p 8080:8080 {{ImageID#}}

Here we have:
-it makes it run interactive
-p assigns ports, which is set up as VM_Port:Local_Machine_Port

Other useful tags:
-d run container in detatched state from terminal
-e set enviroment variables

Docker Compose

Docker compose is a useful way to build images and run containers all in one command. To run docker-compose, you must write a docker-compose.yml file. For more info, see Docker's Compose documentation : https://docs.docker.com/compose/compose-file/

Fun Stuff

Reset which docker-machine you are using to "default":
eval "$(docker-machine ip default)"

View list of available VMs on your computer:
docker-machine ls

You can override the commands of the run by adding the desired command to the end of the run command. For example: docker run -it -p 8080:8080 {{ImageID#}} echo hello world

Useful commands:
docker ps : shows all currently running containers
docker ps -a : shows all containers
docker images : shows all loaded images
docker rm [id] : remove a container
docker rmi : remove an image