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Yo, Dawg, I heard you like abstraction layers

In theory, I could run all my scripts, projects, etc, as daemons or applications on the base OS of each of my servers.

In theory. In practice, that turned out to be a bad idea: hard drives died, dependencies differed between applications, it was all a mess. So I drank the container cool-aid. It’s tasty.

In the brave, new container-world, I’m running all my stuff on Kubernetes (more on this in the kubernetes section). So I need to install that…presumably in a bunch of VMs. In a previous iteration of the lab, I learned (the hard way) that hand-installing kubernetes and hand-building the VMs for it is a pain in the neck. So I wanted to run the VMs for the kubernetes infrastructure in a managed/scriptable container/VM system.

Enter LXD.

WTF is lxd?

LXD is a virutalization system built as an extension of LXC.

So WTF is LXC?

LXC is a container management system built on top of Linux virtualization controls.

LXC is kinda like docker (Docker used to use LXC under the hood, but moved away from it a while ago), and LXD built on top of that to offer new capabilities like live migration, snapshots, etc. Because they’re still containers, it doesn’t take as much overhead to run a VM through LXC/LXD as it would with a regular Virtualization system like KVM. But, because they’re VMs, each VM gets their own networking stack, making it easier to get the applications you deploy in an LXD node to talk to other things (or have other things talk to it). In fact, LXD builds in an “Overlay” network where it assigns IP addresses to it’s nodes and handles routing traffic between them automatically.

Tonight, we install.

Having decided on a container/VM system, it’s time to install it. I have 3 RAID-1 volumes on each machine: the OS, and 2 storage volumes (called, creatively, “data1” and “data2”). I made “data1” and “data2” the storage locations for the lxd system, to hold the base images for the virtual machines, etc. I configured LXD in a cluster, so that the two systems will share resources between them when deciding where to launch a new container or VM.

Aside: I had to install LXD via Ubuntu’s snap system. For reasons that I understand, but find regrettable, Ubuntu is trying to move everything away from the debian-based apt system and over to snap. This means that projects like LXD will only get updates in the snap version of the application. My Ubuntu 18.04 systems didn’t already have snap installed, so I had to do:

sudo apt-get install snap

(Note If snap already exists, that won’t break anything. If it doesn’t, you’ll get snap. Hooray.)

Next, I needed to install LXD (which will also install lxc and a few other things). In Ubuntu 18.04LTS they include an older version of LXD in apt, which only caused confusion and delay. I had to uninstall that, then install lxd via snap:

sudo apt-get remove lxd lxd-client lxcfs liblxc-common liblxc1 lxc-utils lxc-common  --purge
snap install lxd

Next I set up the first LXD daemon.

lxd init

After some experimentation, I learned that it’s important to not choose –auto for this step.

Anyway, this command launched an interactive set-up prompts to configure LXD. Most of the answers to these questions were obvious, and the defaults reasonable, but I had to make sure to say that I was making a cluster. This is the point where the serious note-taking started, since the cluster configuration answers were important: on the first machine I set the password to join the cluster, created the new bridge and fan overlay network, etc. Other than the password, the defaults here seemed reasonable to me (see previous comments about making things as vanilla as possible).

My only concession to configuration was setting up storage. Since I’d configured the Google boxes with 3 RAID 1’s, I wanted to use the non-OS-holding RAIDs for container storage. That meant I had to configure that in LXC. That’s fairly easy:

	lxc storage create data1 dir source=/data1/lxd
	lxc storage create data2 dir source=/data2/lxd
	lxc storage create default dir source=/data1/lxd-default
	lxc profile device add default root disk path=/ pool=default

This made /data1 the place where the actual containers will live, and gave me two other pools to use to store other stuff (if using juju to make a new container, for example, I could add “storage=data2” to the create command and it would be stored on the /data2 path).

I did all of this on the first machine, because when running the commands on the second machine to join the cluster, it mostly just inherited the configuration from the first. The second lxd init command will ask if you want to make a cluster, then ask for the URL of the first server, and the password. It then asked me for the paths to match the storage pools created on the first box, I entered those the same way they were on the first one, since the two boxes should be identical.

At that point, I was done with LXD/LXC setup. I had a working 2-node cluster. For more general safety, I should have three machines to make this a real cluster. When I get more money I’ll get another Google box and some drives…this will do for now.