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Create custom AMIs using Ansible for provisioning.
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README.md

AMI Creator

Automates creating custom AMIs using Ansible for provisioning.

  1. Create a temporary EC2 instance
  2. Upload and run a pre-provisioning script
  3. Run Ansible against the instance
  4. Create AMI
  5. Terminate instance

Each of these steps can be run individually to allow for debugging and fine-tuning your instance before creating the final AMI.

$ ami-creator help

NAME
        ami-creator

DESCRIPTION

        ami-creator is a command line tool to build custom AMIs using Ansible for provisioning.

OPTIONS

        --version   Display the version of this tool.

AVAILABLE COMMANDS

    init                Create a new project
    create              Create a custom AMI start to finish
    pre-ansible         Run a script on the instance before running Ansible
    ansible             Run Ansible on the instance
    ssh                 SSH to the currently running instance
    finalize            Create AMI from currently running instance
    terminate           Terminate the currently running instance
    list-amis           List AMIs created on a per-session, per-project or global basis
    list-instances      List any instances that are running on a per-session, per-roject or global basis

Getting started

AWS resources

Performing actions in your AWS account requires several resources to exist prior to creating custom AMIs. Specifically:

  • AWS CLI profile
  • EC2 SSH Key
  • EC2 SSH File, e.g. ~/.ssh/ami-creator.pem
  • EC2 Security Groups, e.g sg-baf872c8
  • EC2 Subnet, e.g subnet-7a742b20
  • EC2 IAM Instance Profile

You will be prompted for these values when creating a new project, so it is a good idea to set them up first.

You basically have three options for creating these resources:

  1. Use existing resources.

  2. Create new ones.

  3. Use cloudformation.json to create a separate ami-creator stack for you.

    cloudformation.json has the added benefit of being completely separate from your existing resources. Don't like ami-creator? Just delete the stack, and there will be no traces of it in your AWS account.

Installation

Pre-requisites:

  • Ansible

  • AWS CLI tools

    I suggest a creating separate profile reserved for ami-creator to use. The cloudformation.json will create a separate user with all the permissions you need. You'll need to manually create the access key and aws profile for this user.

    Alternatively, you can attach the ami-creator-user policy created by cloudformation.json to an existing user or group.

# checkout the git repo
$ git clone git@github.com:crucialwebstudio/ami-creator.git

# symlink ami-creator.sh to somewhere on your $PATH
$ ln -s /path/to/ami-creator.sh /usr/local/bin/ami-creator

Now you can call ami-creator from anywhere.

Create ami-creator directory in your Ansible folder

$ cd /path/to/ansible
$ mkdir ami-creator

Creating a project

Call ami-creator init from within the ami-creator directory.

$ cd /path/to/ansible/ami-creator
$ ami-creator init

This will prompt you for several project variables and save several files to a new project folder.

Creating an AMI

$ cd /path/to/ansible/ami-creator/name-of-project
$ ami-creator create

This should start a new 'session' and a custom AMI from start to finish. If any of the steps fail, the instance will still be running so you can debug and tweak your instance. ami-creator includes several commands to help with debugging a 'session'.

$ ami-creator ssh
$ ami-creator pre-ansible
$ ami-creator ansible
$ ami-creator finalize
$ ami-creator terminate

Viewing resources

Instances and AMIs are tagged so they are easily discoverable by ami-creator. These commands will show you what resources are associated with ami-creator,

Listing Instances

$ ami-creator list-instances

AMI creator prompts you to terminate the temporary instance after a new AMI is successfully created. If you answered no or some other step of the process fails such that the instance is not terminated, this command will list any instances that were created by ami-creator.

You can manually terminate any running instances with

$ ami-creator terminate

Listing AMIs

$ ami-creator list-amis

AMIs are tagged so they are easily discoverable on a per-session, per-project, or global basis. This command will list them for you.

Project Directory Structure

The ami-creator folder lives inside your Ansible directory structure. AMI Creator projects live in folders below that.

ami-creator/
    project-name/
        ansible.sh
        inventory.ini
        playbook.yml
        pre-ansible.sh
        project.cfg
        session.lock
        ssh.cfg
group_vars/
host_vars/
roles/
someproject.playbook.yml

Description of files

  • ansible.sh

    This is a wrapper around ansible-playbook.

    • Feel free to modify, but be careful to retain the existing parameters.
  • inventory.ini

    This is an Ansible inventory file that represents the temporary EC2 instance.

    • Feel free to modify, but be careful to retain the ami-creator hostname.
  • playbook.yml

    This playbook is copied from your existing Ansible directory. The main difference is the hosts variable is set to ami-creator, e.g. hosts: ami-creator, so that AMI Creator can run the playbook against the temporary EC2 instance.

    AMI Creator does not touch your existing playbooks. You can modify your current playbooks at-will and AMI Creator will copy the changes to this file.

    • Do not modify
  • pre-ansible.sh

    This script is copied to and executed on the temporary EC2 instance prior to running Ansible.

    • Feel free to modify.
  • project.cfg

    The contains project configuration variables set during ami-creator init

    • Feel free to modify values. Do not add or modify variable names.
  • session.lock

    This holds variables saved during a session such as the Instance ID and the AMI ID.

    • Do not modify.
  • ssh.cfg This is an SSH config file to help with SSH-ing to the temporary EC2 instance.

    • Do not modify.

F.A.Q.

  1. Why did you create this tool?

    Creating custom AMIs is tedious. This started as an internal tool to help me automate the process and it currently "works for me". I'd love to have you try it out and let me know if you find it useful.

  2. Why does the ami-creator folder have to exist within my Ansible folder?

    Technically, it doesn't, but this convention makes it easy for ami-creator to locate your playbooks, roles, etc. Additionally, your playbooks are (hopefully) already under source control. I believe if you are using a tool such as ami-creator to create custom AMIs, the files it uses and creates are important enough to have under source control as well. This enables code review, sharing with a team, etc.

  3. Pure Bash, eh?

    This may get rewritten in Python at some point. For now it works pretty well and there are no dependencies.

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