Continuous Delivery for Docker
Read how Continuous Delivery for Docker works with Shippable and what is supported. Learn how to configure your CD workflows and use our various third party integrations to connect the tools you already use and love.
Why Docker?
Containers have been around for a long time, but never found mainstream acceptance because using them was complicated. An open source project Docker changed the game by simplifying container workflows and this has resulted in a lot of excitement around using containers in all stages of the software delivery lifecycle, from development to production.
Docker has become so mainstream in the short time since it debuted in 2013 that the big giants like Amazon, Cisco, Google, Microsoft Red Hat, VMWare, and others have created the Open Container Initiative to develop a common standard around it.
Docker vs VMs
Virtual machines (VMs) are an abstraction of physical hardware. Using a layer called a hypervisor, you can run multiple 'virtual' machines on one physical machine. Each VM includes a full copy of an operating system, as well as applications and the required binaries and libraries.
Docker, just like any container technology, offers abstraction at the application layer. The host OS is shared by all containers running on the host and each container packages applications and the required binaries and libraries. Each container runs as an isolated process in user space. Since they do not include a copy of the OS, Docker containers are very lightweight when compared to VMs.
Here are the pros and cons of using Docker vs VMs. In most cases, you don't have to make a choice of one vs the other. Docker and VMs are better together and you can run containers on VMs.
Pros of using Docker
- Docker containers start up almost instantly since they're lightweight and use less compute and RAM. You can also run more containers on a machine than VMs.
- Images are constructed from filesystem layers and share common files. This minimizes disk usage and image downloads are much faster.
- Docker apps are portable since they follow the 'Build Once, Run Anywhere' mantra.
- You can benefit from the rich collection of public images from Docker Hub and use that as a starting point to build your own image.
- Docker makes it easier to adopt a microservices architecture since each service can be shipped in a lightweight container.
Cons
- While Docker has made great advances in container security, VMs are still the right choice if you want complete isolation .
- Docker helps with breaking down your app into microservices, but unless you have the processes and automation in place, having many services that are shipped independently might end up complicating your software delivery workflow and slowing you down.
