|LXD logo from Ubuntu blog|
It is expensive to make (and test) adjustments to the software that allow it to run in a non-standard manner.
Maintaining a swarm of snowflakes is not a scalable business practice. More deployment variations means more documentation and more pairs of hands needed to manage them. Uniformity and automation are what keep our prices competitive.
Opposing the engineering team's desire for uniformity is the practical need to fit our solution into the customers data-centre and budget. We can't define a uniform physical infrastructure that all of our customers must adhere to. Well, I suppose we could, but we would only have a very small number of customers who are willing and able to fit their data-centre around us.
We are therefore on the horns of a dilemma. Specifying standard physical hardware is impractical and limits the sales team. Allowing the sales team to adjust the infrastructure means that we have to tailor our platform to each deployment.
Virtualization is the rational response to this dilemma. We can have a standard virtualized infrastructure and work with the sales team and the customer to make sure that the hardware is able to support this. This way we'll know that our software is always deployed on the same platform.
LXD is a hypervisor for containers and is an expansion of LXC, the Linux container technology behind Docker. It's described by Stéphane Graber, an Ubuntu project engineer,as a "daemon exporting an authenticated representational state transfer application programming interface (REST API) both locally over a unix socket and over the network using https. There are then two clients for this daemon, one is an OpenStack plugin, the other a standalone command line tool."
It's not a replacement for Docker, even though Linux kernel provided containers are at the root of both technologies. So what is LXD for? An LXD container is an alternative to a virtual machine running in a traditional hypervisor.
With virtualization (or LXD containerization), if your customer has limited rack-space or a limited budget you can still sell your software based on a standard platform. You can take what metal is available and install LXD containers to partitition the resources up into separated "machines".
If you like, you can use Docker to manage the deployment of your software into these LXD containers. Docker and LXD are complementary!
In practical terms you can use tools like Ansible to automate the provisioning of your LXD containers on the customers metal. You are able to define in code the infrastructure and platform that your software runs on. And that means your engineering team wins at automation and your sales team wins at fitting the software into the customer data-centre.