Versioning

For anything more than the basics you should have a "Bakery" a CI tool and process in place that regular builds new images. A Scenario where AMI's are built routinely.

This creates its own set of problems.

Greatest of which are "How do I know which AMI is the best?", "How do build a new Imagine and Not Break something" and "Which of these Images has been tried and tested?"

The Images/AMIs themselves are a software Artifact and should have a development process like others do.

When you build a Java library you version it, and you can do the same with Packer images if you name or tag it with a Build number. "But I already have a git hash?" The git hash does identify it, but it doesn't work well with Humans, QA or ordering. Thanks Git.

A basic numbering Scheme

You can use semantic versioning or any scheme you like, but use Semantic or AKA SemVer.

Most CI tools, that you might drive your "Bakery" will provide/expose and/or sn environmental variable or BUILD_NUMBER that can be used.

Add a variable to your template, such as BUILD_NUMBER and this will to pull the environment variable BUILD_NUMBER into Packer.

  "build_number": "{{env `BUILD_NUMBER`}}",

Then modify the AMI name to reflect the new scheme:

  "ami_name": "RHEL-BASE-v{{user `build_number`}}-{{timestamp}}-AMI",

With the version in the name you can now refer to it in your Terraform:

data "aws_ami" "rhelbase" {
  most_recent = true

  filter {
    name   = "name"
    values = ["RHEL-BASE-v${var.version}*"]
  }
}

You can also use the same AMI filters in your Packer Template

"source_ami_filter": {
        "filters": {
            "virtualization-type": "hvm",
            "name": "RHEL-7.6_HVM_GA-*",
            "root-device-type": "ebs"
            },
          "owners": [
            "309956199498"
          ],
          "most_recent": true
      },

This filter will get the latest RHEL 7.6 that's published by AWS account 309956199498 also known as Red Hat.

Finding AMI'S

It's much quicker to find AMI's details via the commandline. (https://aws.amazon.com/blogs/compute/query-for-the-latest-amazon-linux-ami-ids-using-aws-systems-manager-parameter-store/)

Via Powershell

```powershell tab="Powershell" aws ec2 describe-images --filter Name="name",Values="CentOS7*"|convertfrom-json aws ec2 describe-images --filter Name="ProductCode",Values="aw0evgkw8e5c1q413zgy5pjce"|convertfrom-json

```Bash tab="Bash"
aws ec2 describe-images \
 --owners 679593333241 \
 --filters \
 Name=name,Values='CentOS Linux 7 x86_64 HVM EBS\*' \
 Name=architecture,Values=x86_64 \
 Name=root-device-type,Values=ebs \
 --query 'sort_by(Images, &Name)[-1].ImageId' \
 --output text

Sharing AMI's across regions

Packer exposes the property ami_regions for this, however it takes an age as it copies the resulting Volumes between regions, so that'll cost you doubly. It pains me but it might be better to build the same project in each region you need it.

Sharing to other accounts

Again Packer has a variable for this:

"ami_users": "{{ user `ami_users` }}",

Which I have exposed as a variable. You can add a list of AWS account numbers to share it to. You don't need to have access to those accounts to share it with them.

pip install future
pip install aws-amicleaner
amicleaner --version

amicleaner --check-orphans --full-report --keep-previous 20

amicleaner --mapping-key tags --mapping-values Application --full-report --keep-previous 20