Let's talk about Ansible

Let's talk about Ansible

Basics of Ansible with EC2 and Terraform

Dipankar Das's photo
Dipankar Das
ยทAug 18, 2022ยท

5 min read

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Table of contents

What is Ansible

Basically, Ansible is a configuration management tool used to configure multiple computers/servers at the same time without manual inputs to each one of them

It is Push based configuration tool thereby eliminating the need to install each server thus agentless another good feature is configuration in YAML which is very easy to write and understand

Architecture

image.png

each playbook can have 1 or more plays and each play has its hosts mentioned each task has 1 or more steps with each having a name and special Ansible bulletin, etc.

---

- name: play 1
   hosts: monitor
   tasks:
    ....
- name: play 2
   hosts: application
   tasks:
    ....

so where do these hostnames come from

Here comes the part of the Inventory

Inside /etc/ansible/hosts file

it can be DNS names or simply put IP address instead

[monitor]
server01.com
server02.com

[application]
server05.com
server07.com
server08.com

Ansible in itself is a CLI, but we can also use GUI by using Ansible Tower

Configure EC2 instance using Ansible (BASIC)

๐Ÿ’ Used the ubuntu 22.04 as an image for EC2 and added HTTP inbound traffic to the security group and the newly created ssh key must be used in your case

Ansible.cfg (/etc/ansible/ansible.cfg)

[defaults]
private_key_file = demo-key-pair.pem # file path ssh key downloaded from AWS

Inventory (/etc/ansible/hosts)

[ec2]
<public ip of ec2 instance> ansible_ssh_user=ubuntu ansible_ssh_pass=<if any>
# but as we are using pem files we don't require the ansible ssh pass tag

To verify the connections

ansible ec2 -m ping -vvv

Playbook

---
- name: My first play
  hosts: ec2
  #  remote_user: root
  become: true
  tasks:
  - name: Ping my hosts
    ansible.builtin.ping:
  - name: Print message
    ansible.builtin.debug:
      msg: Hello from preview runner!!!
  - name: install docker
    ansible.builtin.shell: "sudo apt update -y && sudo apt install docker.io -y"

  - name: fix the permissions
    ansible.builtin.shell: "sudo usermod -aG docker ${USER}"

  - name: run container
    ansible.builtin.shell: "sudo docker network crnewly created ssh key must beeate pdf ; sudo docker run --rm -d --net pdf -p 80:80 --name pdf dipugodocker/pdf-editor:0.8-frontend && sudo docker run --rm -d --net pdf -p 8080 --name backend dipugodocker/pdf-editor:0.8-backend"

  - name: "GET docker compose file" # demonstration of how to copy files
    ansible.builtin.copy:
      src: docker-compose.yml
      dest: /home/ubuntu
      owner: ubuntu
      group: ubuntu
      mode: '0744'

EC2 playbook syntax check

ansible-playbook ec2-demo.yml --syntax-check

NOTE: if sudo privileges are asked use --ask-become-pass if we get asked for sudo passphrase during privilege escalation

ansible-playbook ec2-demo.yml

Here is a little tip for viewing the status of all EC2 instances using AWS CLI

aws ec2 describe-instances

Let's go a step further!

Lets configure terraform with Ansible to automate the infrastructure and configuration

โš  NOTE: Comment out every line in the /etc/ansible/hosts

Terraform file

provider "aws" {
  region  = "us-east-1"
}

# $ export AWS_ACCESS_KEY_ID="<provide the keys>"
# $ export AWS_SECRET_ACCESS_KEY="<provide the keys>"

# 1. create vpc
resource "aws_vpc" "prod-vpc" {
  cidr_block = "10.0.0.0/16"

  tags = {
    "Name" = "production"
  }
}

# 2. create internet gateway
resource "aws_internet_gateway" "gw" {
  vpc_id = aws_vpc.prod-vpc.id

  tags = {
    Name = "ig"
  }
}

# 3. create custom route table
resource "aws_route_table" "prod-route-table" {
  vpc_id = aws_vpc.prod-vpc.id

  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_internet_gateway.gw.id
  }

  route {
    ipv6_cidr_block        = "::/0"
    gateway_id             = aws_internet_gateway.gw.id
  }

  tags = {
    Name = "prod-rt"
  }
}

# 4. create a subnet
resource "aws_subnet" "subnet-1" {
  vpc_id     = aws_vpc.prod-vpc.id
  cidr_block = "10.0.1.0/24"
  # cidr_block = var.subnet_prefix
  availability_zone = "us-east-1a"

  tags = {
    Name = "prod-subnet"
  }
}

# 5. associate subnet with route table
resource "aws_route_table_association" "a" {
  subnet_id      = aws_subnet.subnet-1.id
  route_table_id = aws_route_table.prod-route-table.id
}

# 6. create a security group to allow ports 22, 80, 443
resource "aws_security_group" "allow_web" {
  name        = "allow_web_traffic"
  description = "Allow Web inbound traffic"
  vpc_id      = aws_vpc.prod-vpc.id

  ingress {
    description      = "HTTP"
    from_port        = 80
    to_port          = 80
    protocol         = "tcp"
    cidr_blocks      = ["0.0.0.0/0"] # so as to make anyone to reach the server
  }

  ingress {
    description      = "SSH"
    from_port        = 22
    to_port          = 22
    protocol         = "tcp"
    cidr_blocks      = ["0.0.0.0/0"] # so as to make anyone to reach the server
  }

  egress {
    from_port        = 0
    to_port          = 0
    protocol         = "-1"
    cidr_blocks      = ["0.0.0.0/0"]
  }

  tags = {
    Name = "allow_web"
  }
}

# 7. create a network interface with ip in the subnet that was created in step 4
resource "aws_network_interface" "web-server-nic" {
  subnet_id       = aws_subnet.subnet-1.id
  private_ips     = ["10.0.1.50"]
  security_groups = [aws_security_group.allow_web.id]
}

# 8. assign an elastic ip to the network interface created in step 7
resource "aws_eip" "one" {
  depends_on = [
    aws_internet_gateway.gw
  ]
  vpc                       = true
  network_interface         = aws_network_interface.web-server-nic.id
  associate_with_private_ip = "10.0.1.50"
}

output "server_public_ip" {  # it will print when terrafrom apply
  value = aws_eip.one.public_ip
}

# 9. create ubuntu server

resource "aws_instance" "web-server-ec2" {
  ami = "ami-052efd3df9dad4825"
  instance_type = "t2.micro"
  availability_zone = "us-east-1a" # it is hardcoded as aws will make different zones to subnet and ec2 creating error
  key_name = "demo-key-pair"
  network_interface {
    device_index = 0
    network_interface_id = aws_network_interface.web-server-nic.id
  }

  user_data = <<-EOF
    #!/bin/bash
    sudo apt update -y
    EOF

  tags = {
    "Name" = "web-server"
  }

# using local-exec to run Ansible
  provisioner "local-exec" {
    command = "sleep 120; ANSIBLE_HOST_KEY_CHECKING=False ansible-playbook -u ubuntu --private-key ./demo-key-pair.pem -i '${aws_instance.web-server-ec2.public_ip},' ec2-cfg.yml && curl --head ${aws_instance.web-server-ec2.public_ip}"
  }
}

here the

  • -u -> user
  • --private-key -> path to the ssh key
  • -i -> inventory with comma separated host IPs

Ansible playbook save as (ec2-cfg.yml)

---
- name: My first play
  # hosts: ec2
  hosts: all
  #  remote_user: root
  become: true # it tells that privilege should be escalated 
  tasks:
  - name: Ping my hosts
    ansible.builtin.ping:
  - name: Print message
    ansible.builtin.debug:
      msg: Hello from preview runner!!!
  - name: install docker
    shell: "sudo apt update -y && sudo apt install docker.io -y"

  - name: fix the permissions
    shell: "sudo usermod -aG docker ${USER}"

  - name: run container
    shell: "sudo docker network create pdf ; sudo docker run --rm -d --net pdf -p 80:80 --name pdf dipugodocker/pdf-editor:0.8-frontend && sudo docker run --rm -d --net pdf -p 8080 --name backend dipugodocker/pdf-editor:0.8-backend"
terraform init
terraform plan
terraform apply

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