Easily build machines images for multiple platforms with the same configuration

Lance Albertson - @ramereth -

Oregon State University Open Source Lab

Attribution-ShareAlike CC BY-SA ©2015

About me

So what is Packer?

Supported Platforms

Amazon EC2 Digital Ocean
Docker GCE
Openstack Parallels
QEMU (kvm) Virtual Box

What problem does Packer solve?


Templates:JSON files containing the build information
Builders:Platform specific building configuration
Provisioners:Tools that install software after the initial OS install
 Actions to happen after the image has been built

Packer Build Steps

This varies depending on which builder you use. The following is an example for the QEMU builder

  1. Download ISO image
  2. Create virtual machine
  3. Boot virtual machine from the CD
  4. Using VNC, type in commands in the installer to start an automated install via kickstart/preseed/etc
  5. Packer automatically serves kickstart/preseed file with a built-in http server

Packer Build Steps

  1. Packer waits for ssh to become available
  2. OS installer runs and then reboots
  3. Packer connects via ssh to VM and runs provisioner (if set)
  4. Packer Shuts down VM and then runs the post processor (if set)
  5. PROFIT!

Variables in Packer

Variables allow you to set API keys and other variable settings without changing the configuration file:

  "variables": {
    "aws_access_key": "",
    "aws_secret_key": ""

  "builders": [{
    "type": "amazon-ebs",
    "access_key": "{{user `aws_access_key`}}",
    "secret_key": "{{user `aws_secret_key`}}",

Environment Variables

You can also use variables to set environment variables within the packer environment that can be used by provisioners.

  "variables": {
    "my_secret": "{{env `MY_SECRET`}}",

Setting variables

You can set variables either via the CLI or importing them from a json file:

# Via CLI
$ packer build \
  -var 'aws_access_key=foo' \
  -var 'aws_secret_key=bar' \

# Via json file
$ packer build -var-file=variables.json template.json

This makes it easy for you to adapt your automated builds as you need fit.

How it works

Packer template file for QEMU:

  "builders": [
      "boot_command": [
        "<tab> text ks=http://{{ .HTTPIP }}:{{ .HTTPPort }}/centos-7.0/ks-openstack.cfg",
      "accelerator": "kvm",
      "boot_wait": "10s",
      "disk_size": 2048,
      "headless": true,
      "http_directory": "http",
      "iso_checksum": "df6dfdd25ebf443ca3375188d0b4b7f92f4153dc910b17bccc886bd54a7b7c86",
      "iso_checksum_type": "sha256",
      "iso_url": "{{user `mirror`}}/7.0.1406/isos/x86_64/CentOS-7.0-1406-x86_64-NetInstall.iso",
      "output_directory": "packer-centos-7.0-x86_64-openstack",
      "qemuargs": [ [ "-m", "1024m" ] ],
      "qemu_binary": "qemu-kvm",
      "shutdown_command": "echo 'centos'\|sudo -S /sbin/halt -h -p",
      "ssh_password": "centos",
      "ssh_port": 22,
      "ssh_username": "centos",
      "ssh_wait_timeout": "10000s",
      "type": "qemu",
      "vm_name": "packer-centos-7.0-x86_64"

How it works


  "provisioners": [
      "environment_vars": [
        "CHEF_VERSION={{user `chef_version`}}"
      "execute_command": "echo 'centos' | {{.Vars}} sudo -S -E bash '{{.Path}}'",
      "scripts": [
      "type": "shell"
  "variables": {
    "chef_version": "provisionerless",
    "mirror": ""

Building the Image

$ packer build centos-7.0-x86_64-openstack.json
qemu output will be in this color.

==> qemu: Downloading or copying ISO
    qemu: Downloading or copying:
==> qemu: Creating hard drive...
==> qemu: Starting HTTP server on port 8081
==> qemu: Found port for SSH: 3213.
==> qemu: Looking for available port between 5900 and 6000
==> qemu: Found available VNC port: 5947
==> qemu: Starting VM, booting from CD-ROM
    qemu: WARNING: The VM will be started in headless mode, as configured.
    qemu: In headless mode, errors during the boot sequence or OS setup
    qemu: won't be easily visible. Use at your own discretion.
==> qemu: Overriding defaults Qemu arguments with QemuArgs...
==> qemu: Waiting 10s for boot...
==> qemu: Connecting to VM via VNC
==> qemu: Typing the boot command over VNC...
==> qemu: Waiting for SSH to become available...

Using the command line

# Build an image from a template
$ packer build template.json

# Inspect at template to see its configuration
$ packer inspect template.json
Optional variables and their defaults:

  chef_version = provisionerless
  mirror       =





# Validate proper json and packer configuration
$ packer validate template.json
Template validated successfully.

Machine readable output

Most commands allow readable output for scripts:

$ packer inspect -machine-readable template.json
1424621191,,ui,say,Optional variables and their defaults:\n
1424621191,,ui,say,  chef_version = provisionerless
1424621191,,ui,say,  mirror       =
1424621191,,ui,say,  qemu
1424621191,,ui,say,  shell


Amazon EC2 Digital Ocean
Docker GCE
Openstack Parallels
QEMU (kvm) Virtual Box

Amazon AMI Builder

Create EBS-backed AMIs by launching a source AMI and re-packaging it into a new AMI after provisioning.
Create instance-store AMIs by launching and provisioning a source instance, then rebundling it and uploading it to S3
Create EBS-backed AMIs from an existing EC2 instance by mounting the root device and using a Chroot environment to provision that device.

Docker Builder


Shell Run either inline or shell scripts
File Uploads Upload files and use shell scripts to move files around as needed
Ansible Provision using playbook and role files
Chef Client Connect to a chef server and run chef
Chef Solo Run a Chef solo run by pointing to local cookbooks or uploading them
Puppet Masterless Run local manifests and modules
Puppet Server Connect to a puppet server and run puppet


Salt Using Salt states, deploy a vm using Salt
PowerShell runs PowerShell scripts on Windows machines
Windows Shell runs scripts using cmd on Windows Machines


Artifice Overrides the artifact list from an upstream builder or post-processor
Atlas Uploads artifacts from your packer builds to Atlas for hosting
compress Compress VMWare or Virtualbox image using gzip
docker-import Imports the docker image locally
docker-push Push image to the docker repository
docker-save Saves docker image directly to a file
docker-tag Tags a build in the docker repository
Vagrant Converts artifact into a valid Vagrant box file
Vagrant Cloud Pushes artifact to Vagrant Cloud
vSphere Uploads artifact to a vSphere endpoint

Extending Packer

Other useful Packer tools


Packer Windows

Demo time!


Lance Albertson - @ramereth -

Oregon State University Open Source Lab

Attribution-ShareAlike CC BY-SA ©2015