I was asked an interesting question: I am about to investigate Docker. We are moving to AWS too. So in your opinion, should I put energy on EC2 Container services or should I put my energy on Docker on EC2? Which is better ? I find this type of question interesting because there’s not, really, a “one size fits all” answer. It depends on your use cases.
In previous posts I’ve gone into some detail around how Docker works, and some of the ways we can use and configure it. These have been aimed at technologists who want to use Docker, and for security staff who want to control it. It was pointed out to me that this doesn’t really help leadership teams. They’re getting shouted at; “We need Docker! We need Docker!”. They don’t have the time (and possibly not the skills) to delve into the low levels the way I have.
One of the big problems with a cloudy environment is in how to allow the application to get the username/password needed to reach a backend service (e.g. a MySQL database). With a normal application the application operate team can inject these credentials at install time, but a cloudy app needs to be able to start/stop/restart/scale without human intervention. This can get worse with containers because these may be started a lot more frequently.
As we’ve previously seen, Docker Swarm mode is a pretty powerful tool for deploying containers across a cluster. It has self-healing capabilities, built in network load balancers, scaling, private VXLAN networks and more. Docker Swarm will automatically try and place your containers to provide maximum resiliency within the service. So, for example, if you request 3 running copies of a container then it will try and place these on three different machines.
In my previous entry I took a quick look at some of the Docker orchestration tools. I spent a bit of time poking at docker-compose and mentioned Swarm. In this entry I’m going to poke a little at Swarm; after all, it now comes as part of the platform and is a key foundation of Docker Enterprise Edition. Docker Swarm tries to take some of the concepts of a single host model and convert it into a cluster.
In earlier posts I looked at what a Docker image looks like and a dig into how it looks at runtime. In this entry I’m going to look at ways of running containers beyond a simple docker run command. docker-compose This is an additional program to be installed, but it’s very common in use. Basically, it takes a YAML configuration file. This can describe networks, dependencies, scaling factors, volumes etc etc.
In the previous entry we looked at how a Docker container image is built. In this entry we’re going to look a little bit about how a container runs. Let’s take another look at the container we built last time, running apache: % cat Dockerfile FROM centos RUN yum -y update RUN yum -y install httpd CMD ["/usr/sbin/httpd","-DFOREGROUND"] % docker build -t web-server . % docker run --rm -d -p 80:80 -v $PWD/web_base:/var/www/html \ -v /tmp/weblogs:/var/log/httpd web-server 63250d9d48bb784ac59b39d5c0254337384ee67026f27b144e2717ae0fe3b57b % docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 63250d9d48bb web-server "/usr/sbin/httpd -.
Container technology, specifically Docker, is becoming an important part of any enterprise. Even if you don’t have development teams targeting Docker you may have a vendor wanting to deliver their software in container form. I’m not so happy with that, but we’re going to have to live with it. In order to properly control the risk around this I feel it helps to have a feeling for the basics of what a Docker container is, and since I come from a technical background I like to look at it from a technology driven perspective.