Chef

Configuration management tool that uses Ruby to define infrastructure as code. Automates infrastructure provisioning and configuration.

Chef Architecture

Component	Description
Chef Workstation	Where you author cookbooks and recipes
Chef Server	Central hub that stores cookbooks and node data
Chef Client	Runs on nodes, applies configurations from server
Chef Supermarket	Community cookbook repository

Chef Client Commands

Client Management

COMMAND	DESCRIPTION
`chef-client`	Run chef client and apply cookbooks
`chef-client -j attributes.json`	Run with custom attributes
`chef-client -W`	Why-run mode (dry-run)
`chef-client -l debug`	Run with debug logging
`chef-client -F json`	Output in JSON format
`chef-client -z`	Local mode (no server)

Configuration

COMMAND	DESCRIPTION
`chef-client -c client.rb`	Use specified config file
`chef-client -k /path/to/client.pem`	Specify client key
`chef-client -s https://chef.example.com/organizations/myorg`	Specify chef server URL
`chef-client -N nodename`	Specify node name

Knife Commands

Knife is Chef's command-line tool for managing the Chef Server.

Client Management

COMMAND	DESCRIPTION
`knife client list`	List all registered clients
`knife client show CLIENT_NAME`	Show client details
`knife client create CLIENT_NAME`	Create new client
`knife client delete CLIENT_NAME`	Delete a client
`knife client reregister CLIENT_NAME`	Regenerate client key
`knife client bulk delete REGEX`	Delete clients matching regex

Node Management

COMMAND	DESCRIPTION
`knife node list`	List all nodes
`knife node show NODE_NAME`	Show node details
`knife node edit NODE_NAME`	Edit node attributes
`knife node delete NODE_NAME`	Delete a node
`knife node from file FILENAME`	Create node from file
`knife node run_list add NODE_NAME 'recipe[cookbook::recipe]'`	Add recipe to node
`knife node run_list remove NODE_NAME 'recipe[cookbook::recipe]'`	Remove recipe from node
`knife node run_list set NODE_NAME 'recipe[cookbook::recipe]'`	Set node run list

Role Management

COMMAND	DESCRIPTION
`knife role list`	List all roles
`knife role show ROLE_NAME`	Show role details
`knife role create ROLE_NAME`	Create new role
`knife role edit ROLE_NAME`	Edit role
`knife role delete ROLE_NAME`	Delete a role
`knife role from file FILENAME`	Create role from file
`knife role run_list add ROLE_NAME 'recipe[cookbook::recipe]'`	Add recipe to role

Cookbook Management

COMMAND	DESCRIPTION
`knife cookbook list`	List all cookbooks on server
`knife cookbook show COOKBOOK_NAME VERSION`	Show cookbook details
`knife cookbook upload COOKBOOK_NAME`	Upload cookbook to server
`knife cookbook upload --all`	Upload all cookbooks
`knife cookbook delete COOKBOOK_NAME VERSION`	Delete cookbook from server
`knife cookbook download COOKBOOK_NAME`	Download cookbook from server

Knife from Supermarket

COMMAND	DESCRIPTION
`knife cookbook site search KEYWORD`	Search cookbooks in supermarket
`knife cookbook site show COOKBOOK_NAME`	Show cookbook details
`knife cookbook site install COOKBOOK_NAME`	Install cookbook from supermarket
`knife cookbook site download COOKBOOK_NAME`	Download cookbook
`knife cookbook site share COOKBOOK_NAME CATEGORY`	Share cookbook to supermarket

Bootstrap (Bootstrapping Nodes)

COMMAND	DESCRIPTION
`knife bootstrap HOSTNAME`	Bootstrap a new node
`knife bootstrap HOSTNAME -x USERNAME -P PASSWORD`	Bootstrap with username/password
`knife bootstrap HOSTNAME -i IDENTITY_FILE`	Bootstrap with SSH key
`knife bootstrap HOSTNAME --sudo`	Bootstrap with sudo
`knife bootstrap HOSTNAME -r 'recipe[cookbook::recipe]'`	Bootstrap with run list
`knife bootstrap HOSTNAME -N NODE_NAME`	Bootstrap with custom node name
`knife bootstrap HOSTNAME -E ENVIRONMENT`	Bootstrap in environment

Search

COMMAND	DESCRIPTION
`knife search node 'role:web'`	Search nodes by role
`knife search node 'platform:centos'`	Search nodes by platform
`knife search node 'chef_environment:production'`	Search nodes by environment
`knife search node 'recipes:apache2'`	Search nodes by recipe
`knife search node 'ipaddress:10.0.0.*'`	Search nodes by IP
`knife search node -a hostname`	Return specific attribute

Chef Resources

Chef resources are the building blocks of recipes.

Common Resources

Resource	Description	Example
`package`	Install/remove packages	`package 'nginx'`
`service`	Manage services	`service 'nginx'`
`file`	Manage files	`file '/etc/config'`
`directory`	Manage directories	`directory '/var/www'`
`template`	Create file from template	`template '/etc/nginx.conf'`
`execute`	Run commands	`execute 'command'`
`user`	Manage users	`user 'deploy'`
`group`	Manage groups	`group 'deploy'`
`cron`	Manage cron jobs	`cron 'backup'`
`git`	Manage git repositories	`git '/opt/app'`

Package Resource

ruby

package 'nginx' do
  action :install
end

# With version
package 'nginx' do
  version '1.18.0'
  action :install
end

# Remove package
package 'nginx' do
  action :remove
end

Service Resource

ruby

service 'nginx' do
  supports status: true, restart: true, reload: true
  action [:enable, :start]
end

# With conditions
service 'nginx' do
  action [:enable, :start]
  only_if { File.exist?('/etc/nginx/nginx.conf') }
end

File Resource

ruby

file '/etc/config.conf' do
  content 'my config content'
  owner 'root'
  group 'root'
  mode '0644'
  action :create
end

# Delete file
file '/tmp/old_file.txt' do
  action :delete
end

Directory Resource

ruby

directory '/var/www/myapp' do
  owner 'www-data'
  group 'www-data'
  mode '0755'
  recursive true
  action :create
end

Template Resource

ruby

template '/etc/nginx/nginx.conf' do
  source 'nginx.conf.erb'
  owner 'root'
  group 'root'
  mode '0644'
  variables({
    port: 80,
    server_name: node['fqdn']
  })
  action :create
end

Execute Resource

ruby

execute 'run_install_script' do
  command '/tmp/install.sh'
  cwd '/tmp'
  user 'root'
  action :run
  not_if { File.exist?('/opt/app/installed') }
end

User Resource

ruby

user 'deploy' do
  comment 'Deployment user'
  uid '1000'
  gid 'deploy'
  home '/home/deploy'
  shell '/bin/bash'
  action :create
end

Group Resource

ruby

group 'deploy' do
  gid '1000'
  members ['deploy']
  action :create
end

Chef Templates (ERB)

Template Example

erb

# nginx.conf.erb
user <%= @nginx_user %>;
worker_processes <%= @worker_processes %>;

events {
    worker_connections <%= @worker_connections %>;
}

http {
    server {
        listen <%= @port %>;
        server_name <%= @server_name %>;

        location / {
            root <%= @document_root %>;
        }
    }
}

Template Usage

ruby

template '/etc/nginx/nginx.conf' do
  source 'nginx.conf.erb'
  variables(
    nginx_user: 'www-data',
    worker_processes: 4,
    worker_connections: 1024,
    port: 80,
    server_name: node['fqdn'],
    document_root: '/var/www/html'
  )
end

ERB Syntax

Syntax	Description
`<%= variable %>`	Output variable value
`<% code %>`	Execute Ruby code (no output)
`<% if condition %>`	Conditional block
`<% else %>`	Else block
`<% end %>`	End block
`<% array.each do	item
`<% end %>`	End loop

Chef Attributes

Attribute Types

Type	Description	Example
`default`	Lowest precedence	`default['nginx']['port'] = 80`
`normal`	Same as default	`normal['nginx']['port'] = 80`
`override`	Higher precedence	`override['nginx']['port'] = 8080`
`automatic`	From Ohai (read-only)	`node['ipaddress']`

Attributes File (attributes/default.rb)

ruby

# attributes/default.rb
default['nginx']['port'] = 80
default['nginx']['worker_processes'] = 4
default['nginx']['worker_connections'] = 1024
default['nginx']['document_root'] = '/var/www/html'

# Override in specific environment
override['nginx']['port'] = 8080 if node.chef_environment == 'production'

Using Attributes

ruby

# In recipe
port = node['nginx']['port']
worker_processes = node['nginx']['worker_processes']

# With default value
port = node['nginx']['port'] || 80

# In template
# nginx.conf.erb
listen <%= node['nginx']['port'] %>;

Chef Recipes

Recipe Structure

ruby

# recipes/default.rb

# Install package
package 'nginx' do
  action :install
end

# Create directory
directory '/var/www/html' do
  owner 'www-data'
  group 'www-data'
  mode '0755'
  action :create
end

# Create configuration from template
template '/etc/nginx/sites-available/default' do
  source 'default.erb'
  variables(
    port: node['nginx']['port'],
    server_name: node['fqdn']
  )
  notifies :reload, 'service[nginx]', :immediately
end

# Enable and start service
service 'nginx' do
  action [:enable, :start]
end

Notification

ruby

# Notifies another resource
template '/etc/nginx/nginx.conf' do
  source 'nginx.conf.erb'
  notifies :reload, 'service[nginx]', :immediately
end

# Subscribes to another resource
service 'nginx' do
  action [:enable, :start]
  subscribes :reload, 'template[/etc/nginx/nginx.conf]', :immediately
end

Guards

ruby

# Only run if file exists
execute 'install_package' do
  command 'apt-get install -y nginx'
  not_if { File.exist?('/usr/sbin/nginx') }
end

# Only run if file doesn't exist
file '/tmp/marker' do
  content 'created'
  only_if { Dir.exist?('/var/www/html') }
end

Chef Cookbooks

Cookbook Structure

cookbook_name/
├── attributes/
│   └── default.rb          # Default attributes
├── definitions/
│   └── my_definition.rb    # Resource definitions
├── files/
│   └── default/
│       └── config.conf     # Static files
├── libraries/
│   └── helpers.rb         # Custom Ruby libraries
├── metadata.rb            # Cookbook metadata
├── recipes/
│   └── default.rb         # Default recipe
├── templates/
│   └── default/
│       └── config.erb     # ERB templates
└── README.md              # Cookbook documentation

Create Cookbook

bash

# Using chef generate
chef generate cookbook my_cookbook

# Generate specific item
chef generate recipe my_cookbook my_recipe
chef generate template my_cookbook my_template
chef generate attribute my_cookbook my_attribute

Metadata.rb

ruby

name 'my_cookbook'
maintainer 'Your Name'
maintainer_email 'you@example.com'
license 'Apache-2.0'
description 'Installs and configures my application'
version '1.0.0'

supports 'ubuntu'
supports 'centos'

depends 'nginx', '~> 10.0'
depends 'mysql', '~> 8.0'

Chef Environments

Environment Management

COMMAND	DESCRIPTION
`knife environment list`	List all environments
`knife environment show ENVIRONMENT`	Show environment details
`knife environment create ENVIRONMENT`	Create new environment
`knife environment edit ENVIRONMENT`	Edit environment
`knife environment delete ENVIRONMENT`	Delete environment

Environment File

ruby

# environments/production.rb
name "production"
description "Production environment"
cookbook_versions({
  "nginx" => "= 10.0.0",
  "mysql" => "= 8.0.0"
})
override_attributes({
  "nginx" => {
    "port" => 8080
  }
})

Chef Best Practices

Use Cookbooks for Reusability - Package related recipes
Use Templates for Configuration - Don't hardcode values
Use Attributes for Customization - Keep recipes flexible
Test Locally - Use Test Kitchen or Chef Solo
Version Control Cookbooks - Git for all cookbooks
Use Community Cookbooks - Don't reinvent the wheel
Follow Naming Conventions - cookbook_name::recipe_name
Document Cookbooks - Include README.md files
Use Roles and Environments - Organize configurations
Monitor Chef Runs - Check logs for errors

Chef vs Other Config Management

Feature	Chef	Puppet	Ansible
Language	Ruby	Puppet DSL	YAML
Agent Required	Yes	Yes	No
Learning Curve	Steep	Steep	Easy
Push Mode	Knife bootstrap	MCollective	Yes
Pull Mode	Yes	Yes	No
Maturity	Mature	Mature	Mature

Useful Tips

Local Testing with Chef Solo

bash

# Run chef solo
chef-solo -c solo.rb -j attributes.json

# solo.rb configuration
file_cache_path "/tmp/chef-solo"
cookbook_path "/tmp/cookbooks"

# attributes.json
{
  "run_list": [
    "recipe[nginx]"
  ]
}

Debugging

bash

# Enable debug logging
chef-client -l debug

# Use why-run mode
chef-client -W

# Check configuration
chef-client --config-file client.rb -c

# Search node data
knife node show NODE_NAME -a attributes

Common Issues

Issue	Solution
`Permission denied`	Check sudo permissions
`Chef::Exceptions::CookbookNotFound`	Upload cookbook to server
`Template not found`	Check template path
`Package not found`	Update package cache
`Syntax error`	Validate recipe syntax with `chef exec ruby -c recipe.rb`

Chef Workstation Installation

bash

# Download from Chef website
curl -L https://omnitruck.chef.io/install.sh | sudo bash

# Install specific version
curl -L https://omnitruck.chef.io/install.sh | sudo bash -s -- -v 18.0

# Verify installation
chef --version
knife --version

Chef ​

Chef Architecture ​

Chef Client Commands ​

Client Management ​

Configuration ​

Knife Commands ​

Client Management ​

Node Management ​

Role Management ​

Cookbook Management ​

Knife from Supermarket ​

Bootstrap (Bootstrapping Nodes) ​

Search ​

Chef Resources ​

Common Resources ​

Package Resource ​

Service Resource ​

File Resource ​

Directory Resource ​

Template Resource ​

Execute Resource ​

User Resource ​

Group Resource ​

Chef Templates (ERB) ​

Template Example ​

Template Usage ​

ERB Syntax ​

Chef Attributes ​

Attribute Types ​

Attributes File (attributes/default.rb) ​

Using Attributes ​

Chef Recipes ​

Recipe Structure ​

Notification ​

Guards ​

Chef Cookbooks ​

Cookbook Structure ​

Create Cookbook ​

Metadata.rb ​

Chef Environments ​

Environment Management ​

Environment File ​

Chef Best Practices ​

Chef vs Other Config Management ​

Useful Tips ​

Local Testing with Chef Solo ​

Debugging ​

Common Issues ​

Chef Workstation Installation ​

Chef

Chef Architecture

Chef Client Commands

Client Management

Configuration

Knife Commands

Client Management

Node Management

Role Management

Cookbook Management

Knife from Supermarket

Bootstrap (Bootstrapping Nodes)

Search

Chef Resources

Common Resources

Package Resource

Service Resource

File Resource

Directory Resource

Template Resource

Execute Resource

User Resource

Group Resource

Chef Templates (ERB)

Template Example

Template Usage

ERB Syntax

Chef Attributes

Attribute Types

Attributes File (attributes/default.rb)

Using Attributes

Chef Recipes

Recipe Structure

Notification

Guards

Chef Cookbooks

Cookbook Structure

Create Cookbook

Metadata.rb

Chef Environments

Environment Management

Environment File

Chef Best Practices

Chef vs Other Config Management

Useful Tips

Local Testing with Chef Solo

Debugging

Common Issues

Chef Workstation Installation