feat: Added Virtual Machines

This commit introduces a new directory structure for managing virtual
machines, specifically tailored for setting up Kubernetes manually on
Ubuntu. Files have been added to the `virtual-machines` directory,
which includes scripts and configurations necessary for the setup.
The following files have been added:
- `README.md`: Documentation for the virtual machines setup.
- `Vagrantfile`: Configuration for Vagrant to manage the virtual machines.
- `ssh.sh`: Script to set up SSH access.
- `tmux.conf`: Configuration file for tmux.
- `update-dns.sh`: Script to update DNS settings.
- `controlplane.sh`: Script to set up the control plane.
- `setup-hosts.sh`: Script to configure the hosts file.
- `vimrc`: Configuration file for Vim.

This commit is part of the ongoing effort to enhance the documentation
and setup instructions for manual installation of Kubernetes. Making
it easier for users to get started with manual installations and
configurations. With the intended purpose of making them more capabale
administrators and users of Kubernetes.

virtual-machines/Vagrantfile

@@ -0,0 +1,254 @@
+# -*- mode: ruby -*-
+# vi:set ft=ruby sw=2 ts=2 sts=2:
+
+# Set the Kubernetes install mode
+# "MANUAL" - This mode adds a jumpbox and leave some networking undone. Its
+#            meant to be used with a guide like "Kubernetes The Hard Way."
+# "KUBEADM"  This mode is similar to the exam,
+#            1. Setup /etc/hosts file on each node transitively.
+#              where where you'll be given
+#            machines that have there hostnames and SSH configured, so you won't
+#            need to know so much networking setup. Also no jumpbox is included.
+INSTALL_MODE = "MANUAL"
+
+BOOT_TIMEOUT_SEC = 120
+
+# Set the build mode
+# "BRIDGE" - Places VMs on your local network so cluster can be accessed from browser.
+#            You must have enough spare IPs on your network for the cluster nodes.
+# "NAT"    - Places VMs in a private virtual network. Cluster cannot be accessed
+#            without setting up a port forwarding rule for every NodePort exposed.
+#            Use this mode if for some reason BRIDGE doesn't work for you.
+BUILD_MODE = "NAT"
+
+# Define the number of worker nodes
+# If this number is changed, remember to update setup-hosts.sh script with the new hosts IP details in /etc/hosts of each VM.
+NUM_WORKER_NODES = 2
+
+# Network parameters for NAT mode
+NAT_IP_PREFIX = "192.168.56"
+JUMPER_IP_START = 10
+CONTROLPLANE_NAT_IP = 11
+NODE_IP_START = 20
+
+# Host operating system detection
+module OS
+  def OS.windows?
+    (/cygwin|mswin|mingw|bccwin|wince|emx/ =~ RUBY_PLATFORM) != nil
+  end
+
+  def OS.mac?
+    (/darwin/ =~ RUBY_PLATFORM) != nil
+  end
+
+  def OS.unix?
+    !OS.windows?
+  end
+
+  def OS.linux?
+    OS.unix? and not OS.mac?
+  end
+
+  def OS.jruby?
+    RUBY_ENGINE == "jruby"
+  end
+end
+
+# Determine host adapter for bridging in BRIDGE mode
+def get_bridge_adapter()
+  if OS.windows?
+    return %x{powershell -Command "Get-NetRoute -DestinationPrefix 0.0.0.0/0 | Get-NetAdapter | Select-Object -ExpandProperty InterfaceDescription"}.chomp
+  elsif OS.linux?
+    return %x{ip route | grep default | awk '{ print $5 }'}.chomp
+  elsif OS.mac?
+    return %x{mac/mac-bridge.sh}.chomp
+  end
+end
+
+# Helper method to get the machine ID of a node.
+# This will only be present if the node has been
+# created in VirtualBox.
+def get_machine_id(vm_name)
+  machine_id_filepath = ".vagrant/machines/#{vm_name}/virtualbox/id"
+  if not File.exist? machine_id_filepath
+    return nil
+  else
+    return File.read(machine_id_filepath)
+  end
+end
+
+# Helper method to determine whether all nodes are up
+def all_nodes_up()
+  if get_machine_id("controlplane").nil?
+    return false
+  end
+
+  (1..NUM_WORKER_NODES).each do |i|
+    if get_machine_id("node0#{i}").nil?
+      return false
+    end
+  end
+
+  if get_machine_id("jumpbox").nil?
+    return false
+  end
+
+  return true
+end
+
+# Sets up hosts file and DNS
+def setup_dns(node)
+  if INSTALL_MODE == "KUBEADM"
+    # Set up /etc/hosts
+    node.vm.provision "setup-hosts", :type => "shell", :path => "ubuntu/vagrant/setup-hosts.sh" do |s|
+      s.args = [NAT_IP_PREFIX, BUILD_MODE, NUM_WORKER_NODES, CONTROLPLANE_NAT_IP, NODE_IP_START]
+    end
+  end
+  # Set up DNS resolution
+  node.vm.provision "setup-dns", type: "shell", :path => "ubuntu/update-dns.sh"
+end
+
+# Runs provisioning steps that are required by masters and workers
+def provision_kubernetes_node(node)
+  # Set up DNS
+  setup_dns node
+  # Set up ssh
+  node.vm.provision "setup-ssh", :type => "shell", :path => "ubuntu/ssh.sh"
+end
+
+# All Vagrant configuration is done below. The "2" in Vagrant.configure
+# configures the configuration version (we support older styles for
+# backwards compatibility). Please don't change it unless you know what
+# you're doing.
+Vagrant.configure("2") do |config|
+  # The most common configuration options are documented and commented below.
+  # For a complete reference, please see the online documentation at
+  # https://docs.vagrantup.com.
+
+  # Every Vagrant development environment requires a box. You can search for
+  # boxes at https://portal.cloud.hashicorp.com/vagrant/discover
+  # config.vm.box = "base"
+
+  config.vm.box = "ubuntu/jammy64"
+  config.vm.boot_timeout = BOOT_TIMEOUT_SEC
+
+  # Set SSH login user and password
+  config.ssh.username = "root"
+  config.ssh.password = "vagrant"
+
+  # Disable automatic box update checking. If you disable this, then
+  # boxes will only be checked for updates when the user runs
+  # `vagrant box outdated`. This is not recommended.
+  config.vm.box_check_update = false
+
+  # Provision controlplane Nodes
+  config.vm.define "controlplane" do |node|
+    # Name shown in the GUI
+    node.vm.provider "virtualbox" do |vb|
+      vb.name = "controlplane"
+      vb.memory = 2048
+      vb.cpus = 2
+    end
+    node.vm.hostname = "controlplane"
+    if BUILD_MODE == "BRIDGE"
+      adapter = ""
+      node.vm.network :public_network, bridge: get_bridge_adapter()
+    else
+      node.vm.network :private_network, ip: NAT_IP_PREFIX + ".#{CONTROLPLANE_NAT_IP}"
+      node.vm.network "forwarded_port", guest: 22, host: "#{2710}"
+    end
+    provision_kubernetes_node node
+    # Install (opinionated) configs for vim and tmux on master-1. These used by the author for CKA exam.
+    node.vm.provision "file", source: "./ubuntu/tmux.conf", destination: "$HOME/.tmux.conf"
+    node.vm.provision "file", source: "./ubuntu/vimrc", destination: "$HOME/.vimrc"
+  end
+
+  # Provision Worker Nodes
+  (1..NUM_WORKER_NODES).each do |i|
+    config.vm.define "node0#{i}" do |node|
+      node.vm.provider "virtualbox" do |vb|
+        vb.name = "node0#{i}"
+        vb.memory = 1024
+        vb.cpus = 1
+      end
+      node.vm.hostname = "node0#{i}"
+      if BUILD_MODE == "BRIDGE"
+        node.vm.network :public_network, bridge: get_bridge_adapter()
+      else
+        node.vm.network :private_network, ip: NAT_IP_PREFIX + ".#{NODE_IP_START + i}"
+        node.vm.network "forwarded_port", guest: 22, host: "#{2720 + i}"
+      end
+      provision_kubernetes_node node
+    end
+  end
+
+  if INSTALL_MODE == "MANUAL"
+    # Provision a JumpBox
+    config.vm.define "jumpbox" do |node|
+      # Name shown in the GUI
+      node.vm.provider "virtualbox" do |vb|
+        vb.name = "jumpbox"
+        vb.memory = 512
+        vb.cpus = 1
+      end
+      node.vm.hostname = "jumpbox"
+      if BUILD_MODE == "BRIDGE"
+        adapter = ""
+        node.vm.network :public_network, bridge: get_bridge_adapter()
+      else
+        node.vm.network :private_network, ip: NAT_IP_PREFIX + ".#{JUMPER_IP_START}"
+        node.vm.network "forwarded_port", guest: 22, host: "#{2730}"
+      end
+      provision_kubernetes_node node
+    end
+  end
+
+  if BUILD_MODE == "BRIDGE"
+    # Trigger that fires after each VM starts.
+    # Does nothing until all the VMs have started, at which point it
+    # gathers the IP addresses assigned to the bridge interfaces by DHCP
+    # and pushes a hosts file to each node with these IPs.
+    config.trigger.after :up do |trigger|
+      trigger.name = "Post provisioner"
+      trigger.ignore = [:destroy, :halt]
+      trigger.ruby do |env, machine|
+        if all_nodes_up()
+          puts "    Gathering IP addresses of nodes..."
+          nodes = ["controlplane"]
+          ips = []
+          (1..NUM_WORKER_NODES).each do |i|
+            nodes.push("node0#{i}")
+          end
+          nodes.each do |n|
+            ips.push(%x{vagrant ssh #{n} -c 'public-ip'}.chomp)
+          end
+          hosts = ""
+          ips.each_with_index do |ip, i|
+            hosts << ip << "  " << nodes[i] << "\n"
+          end
+          puts "    Setting /etc/hosts on nodes..."
+          File.open("hosts.tmp", "w") { |file| file.write(hosts) }
+          nodes.each do |node|
+            system("vagrant upload hosts.tmp /tmp/hosts.tmp #{node}")
+            system("vagrant ssh #{node} -c 'cat /tmp/hosts.tmp | sudo tee -a /etc/hosts'")
+          end
+          File.delete("hosts.tmp")
+          puts <<~EOF
+
+                 VM build complete!
+
+                 Use either of the following to access any NodePort services you create from your browser
+                 replacing "port_number" with the number of your NodePort.
+
+               EOF
+          (1..NUM_WORKER_NODES).each do |i|
+            puts "  http://#{ips[i]}:port_number"
+          end
+          puts ""
+        else
+          puts "    Nothing to do here"
+        end
+      end
+    end
+  end
+end