packer

What it does

How to write it

packer init|fmt|validate|build [OPTIONS] TEMPLATE_OR_DIR

Main parts

Commands

init DIR

Install the plugins in required_plugins.

fmt DIR

Format templates.

validate DIR

Check templates.

build DIR

Build the image(s).

inspect DIR

Show the parts of a template.

console

Try expressions.

plugins install|installed

Manage plugins.

Most used

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$ run as a normal user# run as root (or with sudo)

1. 1The workflow

   $packer init .
   $packer fmt .
   $packer validate .
   $packer build .

2. 2An Azure image template

   $cat rhel-base.pkr.hcl
   packer {
     required_plugins {
       azure   = { source = "github.com/hashicorp/azure", version = "~> 2" }
       ansible = { source = "github.com/hashicorp/ansible", version = "~> 1" }
     }
   }
   source "azure-arm" "rhel" {
     use_azure_cli_auth                = true
     location                          = "westeurope"
     vm_size                           = "Standard_B2s"
     os_type                           = "Linux"
     image_publisher                   = "RedHat"
     image_offer                       = "RHEL"
     image_sku                         = "9-lvm-gen2"
     managed_image_name                = "rhel9-base-${formatdate("YYYYMMDD", timestamp())}"
     managed_image_resource_group_name = "rg-images"
   }
   build {
     sources = ["source.azure-arm.rhel"]
     provisioner "ansible" { playbook_file = "harden.yml" }
     provisioner "shell" {
       inline = ["sudo dnf -y update", "sudo /usr/sbin/waagent -force -deprovision+user && export HISTSIZE=0 && sync"]
     }
   }

3. 3Build with variables

   $packer build -var-file=prod.pkrvars.hcl .

4. 4Build one source only

   $packer build -only=azure-arm.rhel .

5. 5Keep the VM when a step fails, to debug

   $packer build -on-error=ask .

6. 6Build a local QEMU image for the lab

   $packer build -only=qemu.rhel9 .

7. 7Use the image in Terraform

   $cat vm.tf
   data "azurerm_image" "base" {
     name_regex          = "^rhel9-base-"
     sort_descending     = true
     resource_group_name = "rg-images"
   }

8. 8Scan the built image in CI

   $trivy vm --scanners vuln azure:///subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/rg-images/providers/Microsoft.Compute/images/rhel9-base-20261027

9. 9Check the template parts

   $packer inspect .

10. 10Rebuild every month in a pipeline

    $cat .github/workflows/image.yml
    on: { schedule: [{ cron: "0 3 1 * *" }] }

Nothing matches this filter.

Files

*.pkr.hcl

Templates.

*.pkrvars.hcl

Variable values.

Exit codes