NAME¶

debos - Debian OS images builder

SYNOPSIS¶

debos [options] <recipe file in YAML>
debos [--help]
    

Application Options:

  -b, --fakemachine-backend=   Fakemachine backend to use (default: auto)


      --artifactdir=           Directory for packed archives and ostree repositories (default: current directory)


  -t, --template-var=          Template variables (use -t VARIABLE:VALUE syntax)


      --debug-shell            Fall into interactive shell on error


  -s, --shell=                 Redefine interactive shell binary (default: bash) (default: /bin/bash)


      --scratchsize=           Size of disk backed scratch space


  -c, --cpus=                  Number of CPUs to use for build VM (default: 2)


  -m, --memory=                Amount of memory for build VM (default: 2048MB)


      --show-boot              Show boot/console messages from the fake machine


  -e, --environ-var=           Environment variables (use -e VARIABLE:VALUE syntax)


  -v, --verbose                Verbose output


      --print-recipe           Print final recipe


      --dry-run                Compose final recipe to build but without any real work started


      --disable-fakemachine    Do not use fakemachine.
    

DESCRIPTION¶

debos is a tool to make the creation of various Debian-based OS images simpler. While most other tools focus on specific use-cases, debos is designed to be a toolchain making common actions trivial while providing enough rope to do whatever tweaking which might be required behind the scenes.

debos expects a YAML file as input. A general overview of a YAML recipe and of the templating engine used can be found in the https://pkg.go.dev/github.com/go-debos/debos/actions#hdr-Recipe_syntax debos recipe syntax documentation.

debos runs the actions listed in the recipe file sequentially. These actions should be self-contained and independent of each other.

Some of the actions provided by debos to customise and produce images are:

•

apt: install packages and their dependencies with apt

•

debootstrap: construct the target rootfs with debootstrap

•

download: download a single file from the internet

•

filesystem-deploy: deploy a root filesystem to an image previously created

•

image-partition: create an image file, make partitions and format them

•

install-deb: install packages and their dependencies from local deb packages

•

ostree-commit: create an OSTree commit from rootfs

•

ostree-deploy: deploy an OSTree branch to the image

•

overlay: do a recursive copy of directories or files to the target filesystem

•

pack: create a tarball with the target filesystem

•

pacman: install packages and their dependencies with pacman

•

pacstrap: construct the target rootfs with pacstrap

•

raw: directly write a file to the output image at a given offset

•

recipe: includes the recipe actions at the given path

•

run: allows to run a command or script in the filesystem or in the host

•

unpack: unpack files from archive in the filesystem

A full syntax description of all the debos actions can be found in the debos actions documentation.

GET IN TOUCH!¶

💬 Join us on Matrix at #debos:matrix.debian.social to chat about usage or development of debos.

🪲 To report a bug, issue or feature request, create a new GitHub Issue.

❓ Please use the GitHub Discussion forum to ask questions about how to use Debos or to discuss best ways of creating recipes.

INSTALLATION (DOCKER CONTAINER)¶

An official debos container is available:

docker pull godebos/debos
    

See docker/README.md for usage.

USING DEBOS IN GITHUB ACTIONS¶

debos can be run in GitHub Actions using the official container with KVM support for isolated and reproducible builds. The --fakemachine-backend=kvm option is specified to ensure KVM is used as expected:

jobs:


  build:


    runs-on: ubuntu-latest


    container:


      image: ghcr.io/go-debos/debos:main


      options: --device=/dev/kvm


    steps: 


      - uses: actions/checkout@v4


      - run: debos --fakemachine-backend=kvm --print-recipe recipe.yaml
    

INSTALLATION FROM SOURCE (UNDER DEBIAN)¶

sudo apt install golang git libglib2.0-dev libostree-dev qemu-system-x86 \


     qemu-user-static debootstrap systemd-container
export GOPATH=/opt/src/gocode # or whatever suits your needs
go install -v github.com/go-debos/debos/cmd/debos@latest
/opt/src/gocode/bin/debos --help
    

SIMPLE EXAMPLE¶

The following example will create an arm64 image, install several packages in it, change the file /etc/hostname to debian and finally make a tarball of the complete system.

{{- $image := or .image "debian.tgz" -}}
architecture: arm64
actions:


  - action: debootstrap


    suite: trixie


    components:


      - main


      - non-free-firmware


    mirror: https://deb.debian.org/debian


    variant: minbase


  - action: apt


    packages:


      - sudo


      - openssh-server


      - adduser


      - systemd-sysv


      - firmware-linux


  - action: run


    chroot: true


    command: echo debian > /etc/hostname


  - action: pack


    file: {{ $image }}


    compression: gz
    

To run it, create a file named example.yaml and run:

debos example.yaml
    

The final tarball will be named debian.tgz. If you would like to modify the fileame, you can provide a different name for the variable image like this:

debos -t image:"debian-arm64.tgz" example.yaml
    

OTHER EXAMPLE RECIPES¶

See the bundled example recipes for some more detailed example recipes. Additional more detailed example recipes are stored under debos-recipes.

ENVIRONMENT VARIABLES¶

debos reads a predefined list of environment variables from the host and propagates them to the fakemachine build environment. The set of environment variables is defined by environ_vars in cmd/debos/debos.go. Currently the list of environment variables includes the proxy environment variables documented at:

https://wiki.archlinux.org/index.php/proxy_settings

The list of environment variables currently exported to fakemachine is:

http_proxy, https_proxy, ftp_proxy, rsync_proxy, all_proxy, no_proxy
    

While the elements of environ_vars are in lower case, for each element both lower and upper case variants are probed on the host and if found propagated to fakemachine. So if the host has the environment variables HTTP_PROXY and no_proxy defined, both will be propagated to fakemachine respecting the case.

The command line options --environ-var and -e can be used to specify, overwrite and unset environment variables for fakemachine with the syntax:

debos -e ENVIRONVAR:VALUE ...
    

To unset an environment variable, or in other words, to prevent an environment variable being propagated to fakemachine, use the same syntax without a value. debos accepts multiple -e simultaneously.

PROXY CONFIGURATION¶

While the proxy related environment variables are exported from the host to fakemachine, there are two known sources of issues:

•

Using localhost will not work from fakemachine. Use an address which is valid on your network. debos will warn if the environment variables contain localhost.

•

In case you are running applications and/or scripts inside fakemachine you may need to check which are the proxy environment variables they use. Different apps are known to use different environment variable names and different case for environment variable names.

FAKEMACHINE BACKEND¶

debos (unless running debos with the --disable-fakemachine argument) creates and spawns a virtual machine using fakemachine and executes the actions defined by the recipe inside the virtual machine. This helps ensure recipes are reproducible no matter the host environment.

Fakemachine can use different virtualisation backends to spawn the virtual machine, for more information see the fakemachine documentation.

By default the backend will automatically be selected based on what is supported by the host machine, but this can be overridden using the --fakemachine-backend / -b option. If no backends are supported, debos reverts to running the recipe on the host without creating a fakemachine.

Performance of the backends is roughly as follows: kvm is faster than uml is faster than qemu. Using --disable-fakemachine is slightly faster than kvm, but requires root permissions.

Benchmark times for running https://github.com/go-debos/debos-recipes/blob/9a25b4be6c9136f4a27e542f39ab7e419fc852c9/pine-a64-plus/debian.yaml pine-a64-plus/debian.yaml on an Intel Pentium G4560T with SSD: