ｐａｃｋｅｒ－ｂｕｉｌｄｅｒ－ａｒｍ

Packer Builder ARM

---

Overview

Description

This plugin allows you to build or extend ARM system image. It operates in two modes:

• new - creates empty disk image and populates the rootfs on it
• reuse - uses already existing image as the base
• resize - uses already existing image but resize given partition (i.e. root)

Plugin mimics standard image creation process, such as:

• builing base empty image (dd)
• partitioning (sgdisk / sfdisk)
• filesystem creation (mkfs.type)
• partition mapping (losetup)
• filesystem mount (mount)
• populate rootfs (tar/unzip/xz etc)
• setup qemu + chroot
• customize installation within chroot

Demo

The virtualization works via binfmt_misc kernel feature and qemu.

Since the setup varies a lot for different hardware types, the example configuration is available per "board". Currently the following boards are supported (feel free to add more):

• bananapi-r1 (Archlinux ARM)
• beaglebone-black (Archlinux ARM, Debian)
• jetson-nano (Ubuntu)
• odroid-u3 (Archlinux ARM)
• odroid-xu4 (Archlinux ARM, Ubuntu)
• parallella (Ubuntu)
• raspberry-pi (Archlinux ARM, Raspbian)
• raspberry-pi-3 (Archlinux ARM (armv8))
• raspberry-pi-4 (Archlinux ARM (armv7), Ubuntu 20.04 LTS))
• wandboard (Archlinux ARM)
• armv7 generic (Alpine, Archlinux ARM)

Table Of Contents

• ｐａｃｋｅｒ－ｂｕｉｌｄｅｒ－ａｒｍ
• Packer builder ARM
• Overview
  • Description
  • Demo
• Table Of Contents
• Quick start
  • Run in Docker
    • Usage via container from Docker Hub:
    • Usage via local container build (supports amd64/aarch64 hosts):
• Dependencies
• Configuration
  • Remote file
  • Image config
  • Qemu config
• Chroot provisioner
• Flashing
• Other
  • Generating rootfs archive
  • Resizing image
  • Docker
  • CI/CD
  • How is this plugin different from solo-io/packer-builder-arm-image
• Examples
• Troubleshooting

Quick start

git clone https://github.com/connerwill/packer-builder-arm
cd packer-builder-arm
go mod download
go build

sudo packer build boards/odroid-u3/archlinuxarm.json

Run in Docker

This method is useful for macOS users where is no native way to use qemu-user-static (or Linux users, who do not want to setup packer and all the tools).

Docker Hub Container

docker run --rm --privileged -v /dev:/dev -v ${PWD}:/build mkaczanowski/packer-builder-arm build boards/raspberry-pi/raspbian.json

More system packages (e.g. bmap-tools, zstd) can be added via the parameter -extra-system-packages=...:

docker run --rm --privileged -v /dev:/dev -v ${PWD}:/build mkaczanowski/packer-builder-arm build boards/raspberry-pi/raspbian.json -extra-system-packages=bmap-tools,zstd

Local docker container build

Usage via local container build (supports amd64/aarch64 hosts):

Build the container locally:

docker build -t packer-builder-arm -f docker/Dockerfile .

Run packer via the local built container:

docker run --rm --privileged -v /dev:/dev -v ${PWD}:/build packer-builder-arm build boards/raspberry-pi/raspbian.json

⦗ 𝔟𝔞𝔠𝔨 𝔱𝔬 𝔱𝔬𝔭 ⤒ ⦘

Dependencies

• sfdisk / sgdisk
• e2fsprogs
• parted (resize mode)
• resize2fs (resize mode)
• qemu-img (resize mode)

Configuration

The configuration is split into 3 parts:

• remote file config
• image config
• qemu config

Remote file

Describes the remote file that is going to be used as base image or rootfs archive (depending on image_build_method)

"file_urls" : ["http://os.archlinuxarm.org/os/ArchLinuxARM-odroid-xu3-latest.tar.gz"],
"file_checksum_url": "http://hu.mirror.archlinuxarm.org/os/ArchLinuxARM-odroid-xu3-latest.tar.gz.md5",
"file_checksum_type": "md5",
"file_unarchive_cmd": ["bsdtar", "-xpf", "$ARCHIVE_PATH", "-C", "$MOUNTPOINT"],
"file_target_extension": "tar.gz",

The file_unarchive_cmd is optional and should be used if the standard golang archiver can't handle the archive format.

Raw images format (.img or .iso) can be used by defining the file_target_extension appropriately.

Image config

The base image description (size, partitions, mountpoints etc).

"image_build_method": "new",
"image_path": "odroid-xu4.img",
"image_size": "2G",
"image_type": "dos",
"image_partitions": [
    {
        "name": "root",
        "type": "8300",
        "start_sector": "4096",
        "filesystem": "ext4",
        "size": "0",
        "mountpoint": "/"
    }
],

The plugin doesn't try to detect the image partitions because that varies a lot. Instead it solely depend on image_partitions specification, so you should set that even if you reuse the image (method = reuse).

Qemu config

Anything qemu related:

"qemu_binary_source_path": "/usr/bin/qemu-arm-static",
"qemu_binary_destination_path": "/usr/bin/qemu-arm-static"

Chroot provisioner

To execute command within chroot environment you should use chroot communicator:

"provisioners": [
 {
   "type": "shell",
   "inline": [
     "pacman-key --init",
     "pacman-key --populate archlinuxarm"
   ]
 }
]

This plugin doesn't resize partitions on the base image. However, you can easily expand partition size at the boot time with a systemd service. Here you can find real-life example, where a raspberry pi root-fs partition expands to all available space on sdcard.

Flashing

To dump image on device you can use custom postprocessor (really wrapper around dd with some sanity checks):

"post-processors": [
 {
     "type": "flasher",
     "device": "/dev/sdX",
     "block_size": "4096",
     "interactive": true
 }
]   

⦗ 𝔟𝔞𝔠𝔨 𝔱𝔬 𝔱𝔬𝔭 ⤒ ⦘

Other

Generating rootfs archive

While image (.img) format is useful for most cases, you might want to use rootfs for other purposes (ex. export to docker). This is how you can generate rootfs archive instead of image:

"image_path": "odroid-xu4.img" # generates image
"image_path": "odroid-xu4.img.tar.gz" # generates rootfs archive

Resizing image

Currently resizing is only limited to expanding single ext{2,3,4} partition with resize2fs.

This is an often requested feature where an already built image is given and, we need to expand the main partition to accommodate changes made in provisioner step (i.e. installing packages).

To resize a partition you need to set image_build_method to resize mode and set selected partition size to 0.

For example:

"builders": [
  {
    "type": "arm",
    "image_build_method": "resize",
    "image_partitions": [
      {
        "name": "boot",
        ...
      },
      {
        "name": "root",
        "size": "0",
        ...
      }
    ],
    ...
  }
]

Complete examples:

• boards/raspberry-pi/raspbian-resize.json
• boards/beaglebone-black/ubuntu.hcl

Docker

With artifice plugin you can pass rootfs archive to docker plugins

"post-processors": [
    [{
        "type": "artifice",
        "files": ["rootfs.tar.gz"]
    },
    {
        "type": "docker-import",
        "repository": "mkaczanowski/archlinuxarm",
        "tag": "latest"
    }],
    ...
]

CI/CD

This is the live example on how to use github actions to push image to docker image registry:

cat .github/workflows/archlinuxarm-armv7-docker.yml

How is this plugin different from solo-io/packer-builder-arm-image

hashicorp/packer#8462

Examples

For more examples please see:

tree boards/

Troubleshooting

Many of the reported issues are platform/OS specific. If you happen to have problems, the first question you should ask yourself is:

Is my setup faulty? or is there an actual issue?

To answer that question, I'd recommend reproducing the error on the VM, for instance:

cd packer-builder-arm
vagrant up
vagrant provision

Note: For this the disksize plugin is needed if not already installed vagrant plugin install vagrant-disksize

⦗ 𝔟𝔞𝔠𝔨 𝔱𝔬 𝔱𝔬𝔭 ⤒ ⦘

---

→ π GitHub GitLab Repositories Gists dampsock.com connerwill.com ∞ ←