Install

# On RHEL
dnf install -y ansible-core

# On mac 
brew install ansible

SSH setup for remote host

# If you dont already have a ssh key pair
ssh-keygen -t rsa -b 4096

# Copy your public key to host
ssh-copy-id -o StrictHostKeyChecking=no <user>@<ip_address>

Important links

1. ansible.cfg option
2. inventory option
3. playbook keywords
4. all modules
5. fedora systemroles

Run ansible

ansible is for adhoc commands

# List all hosts configured in inventory 
ansible --list-hosts all

# ping
ansible all -m ping # Run on all
ansible g1 -m ping # Run on group of nodes
ansible node1 -m ping # Run on single node named `node1` in inventory file

# command
ansible node1 -m command -a "hostname"

# Gather Facts
ansible node1 -m ansible.builtin.setup  >> node1_facts.json

Run ansible-playbook

# Check Syntax of all playbook in this repo
aplaybook playbooks/* --syntax-check      
ansible-playbook playbooks/index.html.j2 --syntax-check # Should give error

# See what hosts will be targetted. --list-hosts
ansible-playbook -l g123 playbooks/helloworld.yaml --list-hosts

# Run helloworld playbook.
# -u rc -c ssh|local -e variables.yaml -i inventory1 -l subset 
ansible-playbook -i inventory -l all playbooks/helloworld.yaml
ansible-playbook -l all   playbooks/helloworld.yaml # Run on all

# --step , step through each task 1 by 1
ansible-playbook -l node1 playbooks/helloworld.yaml --step

# Playbook to gather facts
ansible-playbook -l node1 playbooks/gatherFacts.yaml 

Imp files

1. inventory
2. on mac
   1. /etc/hosts
   2. /Users/arslankhan/.ssh/config
3. ansible.cfg
4. variable file
   1. good to put it in host_vars folder

Notes

1. Gather facts: is implicit by default i.e. true
2. Quotes: Put single quotes inside double quotes. "''"
   1. Escape single quotes that are used as plain texts not to segment
   2. "command='su root -c \'touch /etc/sudoers.d/rc\'' responses=Password=billu"
   3. Essitially put escape character \ with evertthing except first " before command and first ' before sudo. No escape ch when these " and ' close as well.
3. Command vs Shell: Careful about characters with command module. Some cannot be processed through the shell, so variables like $HOME and operations like "<", ">", "|", and "&" will not work.
   1. In such cases use shell module
   2. command is safer and preferred over shell

Variables

When adding a new host to inventory. Its a good idea to put all its variables in host_vars/<hostname>.yaml file

In Ansible, when dealing with variable precedence, the order of precedence from highest to lowest is as follows:

1. Variables defined in the playbook: These variables are defined within the playbook itself using vars or vars_files directives.
2. Variables defined in inventory: Variables defined within the inventory file or in inventory group_vars or host_vars directories.
3. Variables defined in roles: Variables defined within roles, either in defaults/main.yml, vars/main.yml, or using vars_files.
4. Variables defined in the playbook directory: Variables defined in host_vars takes precedance over group_vars within the playbook directory.
5. Variables defined in the ansible.cfg file: These are global variables set in the ansible.cfg configuration file.
6. Environment variables: Variables set in the environment where Ansible is executed. These take precedence over variables set in configuration files.

# CHECK Which variables a host is picking up or prioritising
ansible-inventory --host node1

ansible-playbook -l node1 playbooks/motd_set.yaml  -e @variables.yaml # Give variables from a file
ansible-playbook -l node1 playbooks/motd_set.yaml -e "motd='FROM CLI : Savvy!'" # Give variable value in CLI
ansible-playbook -l node1 playbooks/motd_set.yaml -e @variables.yaml -e "welcome_message='FROM CLI - Defined'" # Later will be used

Mac

# --connection=local so it does not try to ssh into the mac
ansible-playbook -l localhost playbooks/helloworld.yaml -c local
ansible-playbook -l localhost playbooks/mac.yaml --connection=local

# To run as root
ansible-playbook -l localhost playbooks/mac.yaml --connection=local --ask-become-pass 

Inventory

# list 
ansible-inventory --inventory inventory --list # All details in yaml format
ansible-inventory --list
ansible-inventory --graph                      # All hosts and groups
ansible-inventory --graph --vars               # What variables is each host picking up

# Get info on host
ansible-inventory --host node1

Remote Host

# You can run anisble playbooks on any host as long as you can SSH into that machine
# Install sshpass on mac
brew install sshpass

ansible.cfg

# View current config
ansible-config view

#ansible.cfg preference order
1. ANSIBLE_CONFIG (environment variable if set)  
2. ansible.cfg (in the current directory)  -> `our method`
3. ~/.ansible.cfg (in the home directory)  
4. /etc/ansible/ansible.cfg  

cat <<EOF > /etc/ansible/ansible.cfg
[defaults]
inventory = ./inventory
remote_user = rc
private_key_file = ./keys/id_rsa
ansible_ssh_common_args = -o ControlMaster=auto -o ControlPersist=60s -o 
EOF

Roles

# Install Fedora system roles
ansible-galaxy collection install fedora.linux_system_roles

Using Vaults

# New file
ansible-vault create passwords.yaml

# if password file is encrypted & you are happy to be prompted
ansible-playbook -l node9 playbooks/ping.yaml -e @secrets/passwords-encrypted.yaml --ask-vault-pass

# if password file is encrypted & DO NOT want to be prompted
ansible-playbook -l node9 playbooks/ping.yaml -e @secrets/passwords-encrypted.yaml --vault-password-file secrets/password-vault

# if password file is NOT encrypted
ansible-playbook -l node9 playbooks/ping.yaml -e @secrets/passwords-plaintext.yaml