Getting Going With Docker
UPDATE: Looks like this post is moot as of today 3/24/2016 due to Docker for Mac and Docker for Windows betas coming out
While interviewing for a new gig I was asked to use memcached and they had suggested standing up a docker instance. I have been using docker pretty regularly now after learning much from my previous co-workers and practical usage.
So, on OSX you can install the
docker brew formulas with homebrew. (If you are not using homebrew and cask to manage your installations on OSX you are missing out). I use VirtualBox as my VM hosting tool.
If you haven’t installed (tapped) cask for application (non-CLI, GUI apps) installations, you should do it now:
brew tap caskroom/cask
Now install the items:
brew cask install virtualbox brew install docker-machine docker
On Linux you don’t need docker-machine as you can just use docker directly, but on OSX you need the set up a Linux host through a VM tool like Virtualbox. You need to setup your docker-machine with the following command:
docker-machine create --driver virtualbox default
This creates the docker host on virtualbox and names it default. So when you run
docker-machine ls you will see something like the following:
› docker-machine ls NAME ACTIVE DRIVER STATE URL SWARM DOCKER ERRORS default * virtualbox Running tcp://192.168.99.100:2376 v1.10.3
I created a Dockerfile to create the docker image with the following content:
FROM ubuntu:latest MAINTAINER Jason Meridth <email@example.com> RUN apt-get update && \ apt-get install -y memcached && \ apt-get clean EXPOSE 11211 CMD ["-u", "root", "-m", "1000"] USER daemon ENTRYPOINT memcached
This Dockerfile will do the following:
- create a new image based on the latest Ubuntu docker image on DockerHub.
- set the maintainer to myself
- update the instance
- install memcached
- cleanup the update/install
- expose port 11211 from the instance
- run the arguments against the entry point (memcached)
- set user to daemon
- set entry point to be memcached
After the docker host is create I then built the image with the following command:
docker build -t memcached_img .
-t lets you set a tag on the image so you can use that instead of the unique ID when creating the instance.
To see the new image you run the following:
and you’ll see something like:
› docker images REPOSITORY TAG IMAGE ID CREATED SIZE memcached_img latest ad3d86685ca8 57 minutes ago 211.4 MB ubuntu latest 97434d46f197 4 days ago 188 MB
Note: To delete the image you would use the
docker rmi memcached_img command.
I then created the docker instace based on the new docker image with the following command:
docker run -name memcached_ins -d -p 45001:11211 memcached_img
You should receive the sha of your new container instance. To see the instance information run
docker ps. The result is
› docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 18c82cd27a2d memcached_img "/bin/sh -c memcached" 5 seconds ago Up 5 seconds 0.0.0.0:45001->11211/tcp memcached_ins
As you can see this shows the mapping from the host port of 45001 to the container instance port of 11211 (defaul for memcached).
Note: You may need to add the
-a argument to the
docker ps command to see all container instances (including the ones not currently running).