DevOps Classroom Series – 28/Aug/2020

Bootstrapping one more node

• This time lets create a ubuntu node from azure Refer Here for creating a vm in azure
• Now lets bootstrap this node by using knife command

knife bootstrap 52.152.147.178 -U qtdevops -P motherindia@123 --sudo -N azurenode

• Lets look at node list from command line and ui

Lets create a simple workflow to install git on all of our nodes

• Working Principles:
  1. Before we try to automate any thing in chef, first get to know the manual way of doing it.
  2. Make a list of the commands you need to execute for your application deployment
• How to work the above in chef:
  • In chef to automate the deployment we create cookbooks
    • In this case let me call this as utility cookbook
    • Navigate to your chef-repo/cookbooks folder in the terminal
    • To generate a cookbooks, when we install chefdk, we get a command line tool called as chef. This tool chef has a sub command called as generate

    chef generate --help
    chef generate cookbook --help
    

    
    • From the above documentation our command will be

    chef generate cookbook utility
    

    
    • When we generated the cookbook we got some files and folders as shown below
• Cookbook: cookbook defines a scenario (application deployment) and contains everything that is required to automate the scenario
• We have already understood that cookbook is collection of recipes & many other things, but lets focus on recipes
• In the generated cookbook there is already a folder called as recipes and there is file called as default.rb
• In chef, we write all of recipes inside the recipes folder & the default recipe is default.rb file.
• So recipe will be a .rb file inside recipes folder in a cookbook.
• Chef uses ruby and .rb stands for ruby file. Inside recipes you can use a custom language (DSL) developed by chef or plain ruby.
• We understood that recipe is resources written in a specific order.
• How to write a resource & what is resource
  • Resource is smallest unit of automation in chef where you can describe the desired state
  • The resource syntax in chef is

  <resource_type> 'resource name' do
     <property-1> <value-1>
     ..
     action <action to be performed>
  end
  

  • Example of chef resource

  service 'apache2' do
    action :restart
  end
  

• The manual commands to install git on ubuntu

sudo apt-get update
sudo apt-get install git -y

• For every manual command try to find a chef resource.
  • The easiest way to find a resource is google the pattern of search is apt-get update in chef
  • Open the documentation and look at the highlighted sections
  • The resource code in the recipes/default.rb

  apt_update 'update ubuntu packages' do
      action :update
  end
  

  • Now lets find a resource for apt-get install git
  • Now the recipes/default.rb will be as shown below

  #
  # Cookbook:: utility
  # Recipe:: default
  #
  # Copyright:: 2020, The Authors, All Rights Reserved.
  apt_update 'update ubuntu packages' do
      action :update
  end
  
  apt_package 'git' do
      action :install
  end
  
  

• Now we need to upload cookbook to chef server. The steps for doing that is Refer here

knife cookbook upload --help
knife cookbook upload utility

• Now verify the cookbook in manage.chef.io
• Since the cookbook is uploaded, we need to inform chef server on which nodes this recipe should be executed. Chef does this by a concept called run_list. Consider run_list to be a list of recipes to be executed on the node. In chef every node will have one run_list.
• Select the node on the Server UI and edit the run_list
• Now chef server will execute this cookbook during next convergence. For this session, lets manually force converge. Login into the node and execute

sudo chef-client