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:
- building 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)
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
This method is primarily for macOS users where is no native way to use qemu-user-static, loop mount Linux specific filesystems and install all above mentioned Linux specific tools (or Linux users, who do not want to setup packer and all the tools).
The container is a multi-arch container (linux/amd64 or linux/arm64), that can be used on Intel (x86_64) or Apple M1 (arm64) Macs and also on Linux machines running linux (x86_64 or aarch64) kernels.
NOTE: On Macs: Don't run
go build .(that produces a darwin binary) and then run belowdocker run ...commands from the same folder to avoid the errorerror initializing builder 'arm': fork/exec /build/packer-builder-arm: exec format error(linux packer process within docker fails to load the outside container compiled packer-builder-arm binary due to being a darwin binary). Delete any local binary viarm -r packer-*to solely use the binary already included and provided by the container.
Pull the latest version of the container to ensure the next commands are not using an old cached version of the container :
docker pull mkaczanowski/packer-builder-arm:latest
Build a board:
docker run --rm --privileged -v /dev:/dev -v ${PWD}:/build mkaczanowski/packer-builder-arm:latest build boards/raspberry-pi/raspbian.json
Build a board with 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:latest build boards/raspberry-pi/raspbian.json -extra-system-packages=bmap-tools,zstd
NOTE: In above commands latest can also be replaced via e.g. 1.0.3 to get a specific container version.
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 ${PWD}:/build packer-builder-arm build boards/raspberry-pi/raspbian.json
sfdisk / sgdiske2fsprogsparted(resize mode)resize2fs(resize mode)qemu-img(resize mode)
Configuration is split into 3 parts:
- remote file config
- image config
- qemu config
Describes the remote file that is going to be used as base image or rootfs archive (depending on image_build_method)
"file_urls" : ["http://os.archlinuxarm.org/os/ArchLinuxARM-odroid-xu3-latest.tar.gz"],
"file_checksum_url": "http://hu.mirror.archlinuxarm.org/os/ArchLinuxARM-odroid-xu3-latest.tar.gz.md5",
"file_checksum_type": "md5",
"file_unarchive_cmd": ["bsdtar", "-xpf", "$ARCHIVE_PATH", "-C", "$MOUNTPOINT"],
"file_target_extension": "tar.gz",
Downloads of the file_urls are done with the help of github.com/hashicorp/go-getter, which supports various protocols: local files, http(s) and various others, see https://github.com/hashicorp/go-getter#supported-protocols-and-detectors). Downloading via more protocols can be done by using other tools (curl, wget, rclone, ...) before running packer and referencing the downloaded files as local file in file_urls.
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.
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).
Anything qemu related:
"qemu_binary_source_path": "/usr/bin/qemu-arm-static",
"qemu_binary_destination_path": "/usr/bin/qemu-arm-static"
The arm instruction set (default=armv7l for qemu-arm-static) to be emulated can be defined via the QEMU_CPU variable. To switch to armv6l (check with uname -m as provission command) run packer e.g. via:
QEMU_CPU=arm1176 packer build ...docker run -e QEMU_CPU=arm1176 ...
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.
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
}
]
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
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 accommodate changes made in provisioner step (ie. 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:
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"
}],
...
]
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
For more examples please see:
tree boards/
The repository also includes some arm typical scripts to e.g. resize partitions on first boot or more extensive provision scripts:
tree scripts/
A big resource for packer provisions scripts is the GitHub Actions runner images repository.
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
