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42 lines
2.5 KiB
Markdown
42 lines
2.5 KiB
Markdown
# Introduction
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Let's 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.
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I chose the "[Atomic](https://www.projectatomic.io/)" CentOS/Fedora image for the VM layer because:
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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.
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2. For someone used to administrating servers individually, Atomic is a PITA. You have to employ [tricky](atomic-trick2) [tricks](atomic-trick1) 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.
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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.
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[atomic-trick1]:https://spinningmatt.wordpress.com/2014/01/08/a-recipe-for-starting-cloud-images-with-virt-install/
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[atomic-trick2]:http://blog.oddbit.com/2015/03/10/booting-cloud-images-with-libvirt/
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## Ingredients
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3 x Virtual Machines, each with:
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* CentOS/Fedora Atomic
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* At least 1GB RAM
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* At least 20GB disk space (_but it'll be tight_)
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* Connectivity to each other within the same subnet, and on a low-latency link (_i.e., no WAN links_)
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## Preparation
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### Install Virtual machines
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1. Install / launch virtual machines.
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2. The default username on CentOS atomic is "centos", and you'll have needed to supply your SSH key during the build process. If you're not using a platform with cloud-init support (i.e., you're building a VM manually, not provisioning it through a cloud provider), you'll need to refer to [trick #1][atomic-trick1] and [#2][atomic-trick2] for a means to override the automated setup, apply a manual password to the CentOS account, and enable SSH password logins.
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### Upgrade Atomic
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Run ```atomic host upgrade```, and reboot if necessary.
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## Serving
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After completing the above, you should have:
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* [X] 3 fresh atomic instances, at the latest releases
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* [X] A user belonging to the docker group for administration
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