Packer builder ARM
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 (ie. 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
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)
Quick start
git clone https://github.com/mkaczanowski/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 primarily 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).
Usage via container from Docker Hub:
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
Usage via local container build:
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 ${PWD}:/build packer-builder-arm build boards/raspberry-pi/raspbian.json
Dependencies
sfdisk / sgdiske2fsprogsparted(resize mode)resize2fs(resize mode)qemu-img(resize mode)
Configuration
Configuration is split into 3 parts:
- remote file config
- image config
- qemu config
Remote file
Describes the remote file that is going to be used as base image or rootfs archive (depending on image_build_method)
"file_urls" : ["http://os.archlinuxarm.org/os/ArchLinuxARM-odroid-xu3-latest.tar.gz"],
"file_checksum_url": "http://hu.mirror.archlinuxarm.org/os/ArchLinuxARM-odroid-xu3-latest.tar.gz.md5",
"file_checksum_type": "md5",
"file_unarchive_cmd": ["bsdtar", "-xpf", "$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
}
]
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 often requested feature where already built image is given and we need to expand the main partition to accomodate changes made in provisioner step (ie. installing packages).
To resize a partition you need to select resize mode and set selected partition size to 0, for example:
"image_partitions": [
{
"name": "boot",
...
},
{
"name": "root",
"size": "0",
...
}
],
Complete example: boards/raspberry-pi/raspbian-resize.json
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
Examples
For more examples please see:
tree boards/
