Use Packer to create custom images

Note: Temporary resources will be created during the process of using Packer to create custom images. These temporary resources will be automatically deleted after the build is completed, thus incurring certain charges.

Overview

Packer is a lightweight open-source tool for automated image packaging launched by Hashicorp. Cloud vendors can integrate their own Builder into Packer, and with a single configuration file, they can efficiently and concurrently create consistent images for multi-cloud platforms. Packer can run on commonly used mainstream operating systems. It is not a substitute for software like Chef, Puppet, but integrates and uses these automation configuration tools to pre-install software on images. Combined with tools like UCloud-Global Terraform and Ucloud CLI, it can implement Infrastructure as Code (IaC), continuous integration, and rapid delivery in multi-cloud DevOps scenarios.

As shown in the figure below, Packer integrates tools such as Chef, Shell, Puppet, etc. in the Provisioner to create immutable images containing various software, which are used by cloud hosts of multi-cloud platforms, Docker, etc.

Comparison of Packer and Traditional Console Image Creation

	Console Image Creation	Packer Image Creation
Usage	Click on the console	Build using configuration file
Reusability	Low. The same operation needs to be performed each time, and image consistency cannot be guaranteed, no version management	High. Copy and modify the configuration file, version management possible
Complexity of Operation	High. First, create a cloud host using the base image, and manually log in to the cloud host for deployment, then manually create the image	Low. Execute the configuration file, automatically execute the pre-configured automation script, and then automatically build the image
Creation Time	Long. Procedural operation, requires manual guarding, cannot accurately wait for each process to execute	Short. Automated workflow operation, perfect polling waiting mechanism, seamless connection of each process

Lifecycle of Creating Images with Packer

Users build a JSON template and execute the packer build command to call the UCloud-Global Builder;
Parameter validation is performed in advance to ensure availability;
Create temporary resources related to cloud hosts, EIP, etc. (EIP is not required if configured in an intranet environment);
Connect to the host through SSH or WinRM, etc., and execute the Provisioner process;
Shut down the cloud host and create an image;
Copy the image;
Delete temporary resources such as hosts, EIP, etc.;
Execute the post-processing process (such as local image import, etc.).

Quick Start

Environment Configuration

Install Packer

Install Packer according to the official installation document (opens in a new tab)Install Packer

Configure Default User

Set the keys UCloud-Global_PUBLIC_KEY, UCloud-Global_PRIVATE_KEY and set the project ID UCloud-Global_PROJECT_ID as global environment variables (recommended), or explicitly specify public_key, private_key, project_id in the json file.

Writing a JSON File

Let's take building a custom image with nginx installed as an example. First, create a clean empty folder as the workspace, and switch to this directory, write a JSON specification file (e.g., test.json), as follows:

{
  "variables": {
    "ucloud_public_key": "{{env `UCLOUD_PUBLIC_KEY`}}",
    "ucloud_private_key": "{{env `UCLOUD_PRIVATE_KEY`}}",
    "ucloud_project_id": "{{env `UCLOUD_PROJECT_ID`}}"
  },
  "builders": [
    {
      "type": "ucloud-uhost",
      "public_key": "{{user `ucloud_public_key`}}",
      "private_key": "{{user `ucloud_private_key`}}",
      "project_id": "{{user `ucloud_project_id`}}",
      "region": "cn-bj2",
      "availability_zone": "cn-bj2-02",
      "instance_type": "n-basic-2",
      "source_image_id": "uimage-f1chxn",
      "ssh_username": "root",
      "image_name": "packer-test-basic-bj"
    }
  ],
  "provisioners": [
    {
      "type": "shell",
      "inline": [
        "yum install -y nginx"
      ]
    }
  ]
}

The above defines a UCloud-Global-uhost Builders builder and a provisioners configurator (opens in a new tab). By executing the command packer build test.json, a custom image can be built with one click.

Custom Image Import Image