Vagrant: Create a multi-machine environment

Konstantinos Patronas

Aug 4, 2020·2 min read

Note: this is not a vagrant tutorial, its just a presentation of a Vagrantfile that could do your life easier!.

Vagrant is a tool that allows you very easy to create development environments and small labs. So i have create this script that covers the following needs:

• This script is somehow like a template, with minimum modifications in a config section you can add /remove as many VMs you want
• You can easily modify the resources of each VM.
• It uses the vagrant-hostmanager plugin, this plugin modifies the /etc/hosts file of your computer and makes the VMs accessible from your computer with their hostnames.
• When you do vagrant destroy it reverts any changes to /etc/hosts
• it copies your public key to the VMs for passwordless SSH

Vagrantfile with some inline comments

# -*- mode: ruby -*-
# vi: set ft=ruby :
# Tested environment
# OS: ubuntu 20.04
# Vagrant: 2.2.6
# Hypervisor: virtualbox 6.1
# Box: centos/7
# Required plugin:
# vagrant-hostmanager (1.8.9, globalNETWORK = "192.168.50."
NETMASK = "255.255.255.0" 
# VM machines configuration
# ip address of the vm is NETWORK plus the last part of the IP
HOSTS = {
   #VM_NAME      IP_ADDRESS    RAM(mb)  GUI    BOX
   "slave01" => [NETWORK+"10", 512,     false, 'centos/7'],
   "slave02" => [NETWORK+"11", 512,     false, 'centos/7'],
}
# A trick to read your SSH public key
# Then the public key is appended to /home/vagrant/.ssh/authorized_keys of the VM
ssh_pub_key = File.readlines("#{Dir.home}/.ssh/id_rsa.pub").first.strip
Vagrant.configure("2") do |config|
  # Those are options for the hostmanager plugin
  # hostmanager add records to /etc/hosts to enable
  # guests to guests and host to guests communication with hostnames
  # To enable the plugin
  config.hostmanager.enabled           = true
  # To enable add records to host /etc/hosts
  config.hostmanager.manage_host       = true
  # To enable add records to guest /etc/hosts
  config.hostmanager.manage_guest      = true
  # Not use private ip addresses for the hosts file, set to false
  config.hostmanager.ignore_private_ip = false
  config.hostmanager.include_offline   = true
  HOSTS.each do |(name, cfg)|
    ipaddr, ram, gui, box = cfg
    if ARGV[0] != 'destroy'
       config.vm.provision 'shell', inline: "echo #{ssh_pub_key} >> /home/vagrant/.ssh/authorized_keys", privileged: false
    end
    config.vm.define name do |machine|
       machine.vm.box = box
       machine.vm.provider "virtualbox" do |vbox|
          vbox.gui    = gui
          vbox.memory = ram
          vbox.name   = name
       end
       machine.vm.hostname = name
       # Deleting entries from known_hosts on 'destroy'
       if ARGV[0] == 'destroy'
          puts("Deleting entries from known_hosts")
          system("ssh-keygen -f #{Dir.home}/.ssh/known_hosts -R '#{name}'")
          system("ssh-keygen -R #{ipaddr}")
       end
       machine.vm.network 'private_network', ip: ipaddr, netmask: NETMASK
    end
  end
end

How to use the script

Place the script in a proper directory

$ mkdir -p ~/vagrant/test
$ cp Vagrantfile ~/vagrant/test

Install the vagrant-hostmanager plugin

$ vagrant plugin install vagrant-hostmanager

Edit the Vagrantfile to match your needs

$ vim ~/vagrant/test/Vagrantfile

Start vagrant

$ cd ~/vagrant/test
$ vagrant up

If everything gone well the VMs will boot, and you will be capable to SSH your VMs from the host using their hostnames passwordless.