geek-cookbook/docs/ha-docker-swarm/vms.md

Introduction

We start building our cloud with virtual machines. You could use bare-metal machines as well, the configuration would be the same. Given that most readers (myself included) will be using virtual infrastructure, from now on I'll be referring strictly to VMs.

Ingredients

3 x Virtual Machines, each with:

• CentOS/Fedora Atomic
• At least 1GB RAM
• At least 20GB disk space (but it'll be tight)
• Connectivity to each other within the same subnet, and on a low-latency link (i.e., no WAN links)

Preparation

Install Virtual machines

1. Install Virtual machines
2. Setup super-user access for your admin user, as a member of the "docker" group

I chose the "Atomic" CentOS/Fedora image because:

1. I want less responsibility for maintaining the system, including ensuring regular software updates and reboots. Atomic's idempotent nature means the OS is largely real-only, and updates/rollbacks are "atomic" (haha) procedures, which can be easily rolled back if required.
2. For someone used to administrating servers individually, Atomic is a PITA. You have to employ tricky tricks to get it to install in a non-cloud environment. It's not designed for tweaking or customizing beyond what cloud-config is capable of. For my purposes, this is good, because it forces me to change my thinking - to consider every daemon as a container, and every config as code, to be checked in and version-controlled. Atomic forces this thinking on you.
3. I want the design to be as "portable" as possible. While I run it on VPSs now, I may want to migrate it to a "cloud" provider in the future, and I'll want the most portable, reproducible design.

atomic host upgrade