Packer: Build your First Image
This is a practical version of how to start with Packer by building your first image.
If you would like to understand better what is Packer and why to use it, I suggest reading this version of the post
Install Packer
To install Packer 1.4.5 using a precompiled binary, run the following commands
wget https://releases.hashicorp.com/packer/1.4.5/packer_1.4.5_linux_amd64.zip
sudo unzip -d /usr/sbin packer_1.4.5_linux_amd64.zip
If you would like to install Packer from source (latest), use the following commands
mkdir -p $(go env GOPATH)/src/github.com/hashicorp && cd $_
git clone https://github.com/hashicorp/packer.git
cd packer && make dev
Terminology
- template - this is the JSON configuration file used to define what image we would like to build and how
- builder - a component of Packer which responsible for creating a machine based on your template and turn this machine into an image
- artifact - result of a build. What exactly is the result depends on the builder. Usually it’s the ID of the image or collection of files.
What are we going to do?
First we will create a template which will describe what image we would like to build.
Next, we will validate the template we wrote. Once the template is validated, we will run the actual build process. This process will produce the image we described in the template.
Let’s start :)
Create a template
Create a file called “aws_image.json” with the following content (this is an official example from Hashicorp docs):
{
"variables": {
"aws_access_key": "",
"aws_secret_key": ""
},
"builders": [{
"type": "amazon-ebs",
"access_key": "{{user `aws_access_key`}}",
"secret_key": "{{user `aws_secret_key`}}",
"region": "us-east-1",
"source_ami_filter": {
"filters": {
"virtualization-type": "hvm",
"name": "ubuntu/images/*ubuntu-xenial-16.04-amd64-server-*",
"root-device-type": "ebs"
},
"owners": ["099720109477"],
"most_recent": true
},
"instance_type": "t2.micro",
"ssh_username": "ubuntu",
"ami_name": "packer-example {{timestamp}}"
}]
}
Few notes:
- Getting AMI owner ID isn’t as straightforward as you might expect. This post is great a explanation for how to locate such information
- Be careful with changing instance type to anything other than t2.micro since you might be charged for that. t2.micro qualifies under free-tier so no charge :)
- As you can see we are not providing credentials through the template but by using variables. We’ll pass the values when we will run the build command
Validate the image
Before we actually build the image, let’s verify the template we wrote is valid
$ packer validate aws_image.json
Template validated successfully.
Great, we can proceed to actually building the image.
Note that validating an image doesn’t mean you will not run into issues when building the image but it’s good to validate a template to make sure you didn’t forget to pass must-use options and you don’t have syntax issues.
Build the image
Run the following command
packer build \
-var 'aws_access_key=blip_blop' \
-var 'aws_secret_key=blop_blop' \
aws_image.json
You need to provide your own aws keys so the client can connect to AWS for creating the image. I’m afraid using blip_blop will not work :)
Output
Depends on the builder/template used, you will get slightly different output. This is the output for the AWS template we used
amazon-ebs: amazon-ebs output will be in this color.
==> amazon-ebs: Creating temporary keypair for this instance...
==> amazon-ebs: Creating temporary security group for this instance...
==> amazon-ebs: Authorizing SSH access on the temporary security group...
==> amazon-ebs: Launching a source AWS instance...
==> amazon-ebs: Waiting for instance to become ready...
==> amazon-ebs: Connecting to the instance via SSH...
==> amazon-ebs: Stopping the source instance...
==> amazon-ebs: Waiting for the instance to stop...
==> amazon-ebs: Creating the AMI: packer-example 1371856345
==> amazon-ebs: AMI: ami-19601070
==> amazon-ebs: Waiting for AMI to become ready...
==> amazon-ebs: Terminating the source AWS instance...
==> amazon-ebs: Deleting temporary security group...
==> amazon-ebs: Deleting temporary keypair...
==> amazon-ebs: Build finished.
==> Builds finished. The artifacts of successful builds are:
--> amazon-ebs: AMIs were created:
us-east-1: ami-0c91c71241917ba
You can verify it was created with the following command
aws ec2 describe-images --owners self --region us-east-1
Keep Exploring
That’s it. You have created your first image. Well Done :)
Packer has many features and options to keep exploring and personally, I feel they did good job with their official documentation so I recommend to start there. Enjoy :)
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