3.6 KiB
Virtual Machines
Let's start building our cluster. You can use either bare-metal machines or virtual machines - 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.
!!! note In 2017, I initially chose the "Atomic" CentOS/Fedora image for the swarm hosts, but later found its outdated version of Docker to be problematic with advanced features like GPU transcoding (in Plex), Swarmprom, etc. In the end, I went mainstream and simply preferred a modern Ubuntu installation.
Ingredients
!!! summary "Ingredients" 3 x Virtual Machines, each with:
* [ ] A mainstream Linux OS (*tested on either [CentOS](https://www.centos.org) 7+ or [Ubuntu](http://releases.ubuntu.com) 16.04+*)
* [ ] At least 2GB 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
- Install / launch virtual machines.
- The default username on CentOS atomic is "centos", and you'll have needed to supply your SSH key during the build process.
!!! tip 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 and trick #2 for a means to override the automated setup, apply a manual password to the CentOS account, and enable SSH password logins.
Permit connectivity between hosts
Most modern Linux distributions include firewall rules which only only permit minimal required incoming connections (like SSH). We'll want to allow all traffic between our nodes. The steps to achieve this in CentOS/Ubuntu are a little different...
CentOS
Add something like this to /etc/sysconfig/iptables:
# Allow all inter-node communication
-A INPUT -s 192.168.31.0/24 -j ACCEPT
And restart iptables with systemctl restart iptables
Ubuntu
Install the (non-default) persistent iptables tools, by running apt-get install iptables-persistent, establishing some default rules (dkpg will prompt you to save current ruleset), and then add something like this to /etc/iptables/rules.v4:
# Allow all inter-node communication
-A INPUT -s 192.168.31.0/24 -j ACCEPT
And refresh your running iptables rules with iptables-restore < /etc/iptables/rules.v4
Enable host resolution
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:
192.168.31.11 ds1 ds1.funkypenguin.co.nz
192.168.31.12 ds2 ds2.funkypenguin.co.nz
192.168.31.13 ds3 ds3.funkypenguin.co.nz
Set timezone
Set your local timezone, by running:
ln -sf /usr/share/zoneinfo/<your timezone> /etc/localtime
Serving
After completing the above, you should have:
[X] 3 x fresh linux instances, ready to become swarm nodes
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