Docker, OSX and remote Ubuntu!

It was about time to post something... I've been so lazy, I'm not sure why, but it's been a very long time with little activity. I'm not sure if there's been a lack of productivity, interest, I'm not sure... My excuse is I moved places and I absolutely hated the workspace at the apartment, so I guess if you're not happy with your work environment at home, you just don't work as much off-hours. Anyway, enough with the excuses. Let's talk about something real: docker.

As most of you might know, docker is hot right now. It's nothing new at it's root really, containers (LXC) have been around in linux for like over a decade, and I believe even before that in BSD unices, as jails. They both probably came into fruition as an evolution to the typical Unix chroot segregation. I guess the turning point for containers came as a by-product of virtualization. All of a sudden everybody was, and still is, virtualizing their infrastructure... But if we look a little closer we realize a huge percentage of all server applications run on linux anyways. So virtualizing the entire VM seems a bit expensive in certain contexts and that's where container sound like a badass idea. Containers do have some security issues, that hypervisors have dialed-in, ie. resource isolation, but they provide an elegant, efficient, flexible solution in many scenarios. Anyway, enough with the container intro. So why docker, and why this post?

Docker defines itself as an open platform for building, shipping and running distributed applications. It gives programmers, development teams and operations engineers the common toolbox they need to take advantage of the distributed and networked nature of modern applications. What it really does is provide a set of tools that allow you to define the software that each of the containers must include - no more, no less. It also allows us to architect our application into different microservices, each running in its own container. By defining our applications in this manner we can immediately benefit from the isolation and "packaging", to scale and deploy almost seamlessly, and definitely in a very convenient manner. But also, the added flexibility allows us to spin up fresh environments very quickly, and what's more, take copies of live environments to run on a new endpoint as a developer ecosystem - think about the benefits of that in terms of speeding up development and improving time-to-bugfix. Ok, so you probably already knew all of that... So what's new? Well basically every tutorial out there, if you run OSX wants you to install virtualbox, and then use boot2docker. That works great and it might be the route for 90% of the people. But what if you have a lightweight rig, a macbook air for instance. Or say you actually have a linux VPS. Or you have access to the Google Cloud Platform, wouldn't you maybe want to spare your machine the burden of containerization? I did. In my case I run and underutilize an Ubuntu VPS, so I figured it made the perfect box for my containers, and since docker follows a client-server model, it had to be mad easy. It was, here are the steps.

If you don't already run Homebrew, please do, thank me later.
First you install docker in your OSX machine, the client.

user@macbook:~$ brew install docker
Then jump into your Ubuntu box - we'll call it docker_vps from now on (this should be similar in any linux distro really), and setup docker there. Ubuntu will bring in all the container stuff when you install - on OSX can't do that because LXC containers require a linux kernel. You can actually follow the official docker instructions here. But just for reference, this is what I did: 
user@docker_vps:~$ curl -sSL https://get.docker.com/ | sh
It will prompt you for the sudo password and install everything necessary.
At this stage I'd recommend you setup key-based authentication to your linux box from your OSX machine, but that's really up to you, here's how. Now let's modify docker's default configuration at /etc/default/docker, we need to do this so that docker not only listens on a local unix socket, but also for remote TCP connections (if you wish you can disable local connections altogether, I didn't). 
DOCKER_OPTS="-H tcp://localhost:2375 -H unix:///var/run/docker.sock"
You should now be ready to start-up docker with the new settings, you know the drill: 
user@docker_vps:~$ sudo service docker restart
Also, make sure the service has been added to systemd or upstart (depending on the version of ubuntu you are running), you'll normally want the docker servicee to come up at boot time. At this point, you have two options, poke a hole in your firewall, or run a tunnel to your OSX box. I chose this second option, it's more secure, I just prefer it. We can now switch to the macbook, your OSX client whatever that may be, and open that tunnel up: 
user@macbook:~$ ssh -N -L 2375:localhost:2375 user@docker_vps > /dev/null 2>&1
Once that's done, let's try it out! 
user@macbook:~$ docker -H tcp://localhost:2375 run -i -t ubuntu /bin/bash
Success? You're done! Just one more thing, if you want to avoid having to specify the -H option all the time you can create the DOCKER_HOST environment variable: 
user@macbook:~$ export DOCKER_HOST="tcp://localhost:2375"
Now lets start messing with docker!

Written on August 19, 2015