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https://github.com/funkypenguin/geek-cookbook/
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81 lines
3.6 KiB
Markdown
81 lines
3.6 KiB
Markdown
# Virtual Machines
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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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!!! summary "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.
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!!! tip
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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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### Prefer docker-latest
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Run the following on each node to replace the default docker 1.12 with docker 1.13 (_which we need for swarm mode_):
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```
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systemctl disable docker --now
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systemctl enable docker-latest --now
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sed -i '/DOCKERBINARY/s/^#//g' /etc/sysconfig/docker
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```
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### Upgrade Atomic
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Finally, apply any Atomic host updates, and reboot, by running: ```atomic host upgrade && systemctl reboot```.
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### Permit connectivity between VMs
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By default, Atomic only permits incoming SSH. We'll want to allow all traffic between our nodes, so add something like this to /etc/sysconfig/iptables:
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```
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# Allow all inter-node communication
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-A INPUT -s 192.168.31.0/24 -j ACCEPT
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```
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And restart iptables with ```systemctl restart iptables```
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### Enable host resolution
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Depending on your hosting environment, you may have DNS automatically setup for your VMs. If not, it's useful to set up static entries in /etc/hosts for the nodes. For example, I setup the following:
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```
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192.168.31.11 ds1 ds1.funkypenguin.co.nz
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192.168.31.12 ds2 ds2.funkypenguin.co.nz
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192.168.31.13 ds3 ds3.funkypenguin.co.nz
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```
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## Serving
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After completing the above, you should have:
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```
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[X] 3 x fresh atomic instances, at the latest releases,
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running Docker v1.13 (docker-latest)
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```
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