bootc-image-builder

A container to create disk images from bootc container inputs, especially oriented towards Fedora/CentOS bootc or derivatives.

🔨 Installation

Have podman installed on your system. Either through your systems package manager if you're on Linux or through Podman Desktop if you are on macOS or Windows. If you want to run the resulting virtual machine(s) or installer media you can use qemu.

A very nice GUI extension for Podman Desktop is also available. The command line examples below can be all handled by Podman Desktop.

On macOS, the podman machine must be running in rootful mode:

$ podman machine stop   # if already running
Waiting for VM to exit...
Machine "podman-machine-default" stopped successfully
$ podman machine set --rootful
$ podman machine start

✍ Prerequisites

The package osbuild-selinux or equivalent osbuild SELinux policies must be installed in the system running bootc-image-builder.

🚀 Examples

The following example builds a centos-bootc:stream9 bootable container into a QCOW2 image for the architecture you're running the command on. However, be sure to see the upstream documentation for more general information! Note that outside of initial experimentation, it's recommended to build a derived container image (or reuse a derived image built via someone else) and then use this project to make a disk image from your custom image.

The generic base images do not include a default user. This example injects a user configuration file by adding a volume-mount for the local file to the bootc-image-builder container.

The following command will create a QCOW2 disk image. First, create ./config.toml as described above to configure user access.

# Ensure the image is fetched
sudo podman pull quay.io/centos-bootc/centos-bootc:stream9
sudo podman run \
    --rm \
    -it \
    --privileged \
    --pull=newer \
    --security-opt label=type:unconfined_t \
    -v ./config.toml:/config.toml:ro \
    -v ./output:/output \
    -v /var/lib/containers/storage:/var/lib/containers/storage \
    quay.io/centos-bootc/bootc-image-builder:latest \
    --type qcow2 \
    --local \
    quay.io/centos-bootc/centos-bootc:stream9

Note that some images (like fedora) do not have a default root filesystem type. In this case adds the switch --rootfs <type>, e.g. --rootfs btrfs.

Running the resulting QCOW2 file on Linux (x86_64)

A virtual machine can be launched using qemu-system-x86_64 or with virt-install as shown below; however there is more information about virtualization and other choices in the Fedora/CentOS bootc documentation.

qemu-system-x86_64

qemu-system-x86_64 \
    -M accel=kvm \
    -cpu host \
    -smp 2 \
    -m 4096 \
    -bios /usr/share/OVMF/OVMF_CODE.fd \
    -serial stdio \
    -snapshot output/qcow2/disk.qcow2

virt-install

sudo virt-install \
    --name fedora-bootc \
    --cpu host \
    --vcpus 4 \
    --memory 4096 \
    --import --disk ./output/qcow2/disk.qcow2,format=qcow2 \
    --os-variant fedora-eln

Running the resulting QCOW2 file on macOS (aarch64)

This assumes qemu was installed through homebrew.

qemu-system-aarch64 \
    -M accel=hvf \
    -cpu host \
    -smp 2 \
    -m 4096 \
    -bios /opt/homebrew/Cellar/qemu/8.1.3_2/share/qemu/edk2-aarch64-code.fd \
    -serial stdio \
    -machine virt \
    -snapshot output/qcow2/disk.qcow2

📝 Arguments

Usage:
  sudo podman run \
    --rm \
    -it \
    --privileged \
    --pull=newer \
    --security-opt label=type:unconfined_t \
    -v ./output:/output \
    quay.io/centos-bootc/bootc-image-builder:latest \
    <imgref>

Flags:
      --chown string           chown the ouput directory to match the specified UID:GID
      --tls-verify             require HTTPS and verify certificates when contacting registries (default true)
      --type string            image type to build [qcow2, ami] (default "qcow2")
      --target-arch string     architecture to build image for (default is the native architecture)

Detailed description of optional flags

Argument	Description	Default Value
--chown	chown the output directory to match the specified UID:GID	❌
--rootfs	Root filesystem type. Overrides the default from the source container. Supported values: ext4, xfs, btrfs	❌
--tls-verify	Require HTTPS and verify certificates when contacting registries	`true`
--type	Image type to build	`qcow2`
--target-arch	Target arch to build	❌

The --type parameter can be given multiple times and multiple outputs will be produced.

💡 Tip: Flags in bold are the most important ones.

💾 Image types

The following image types are currently available via the --type argument:

Image type	Target environment
`ami`	Amazon Machine Image
`qcow2` (default)	QEMU
`vmdk`	VMDK usable in vSphere, among others
`anaconda-iso`	An unattended Anaconda installer that installs to the first disk found.
`raw`	Unformatted raw disk.
`vhd`	vhd usable in Virtual PC, among others
`gce`	GCE

💾 Target architecture

Specify the target architecture of the system on which the disk image will be installed on. By default, bootc-image-builder will build for the native host architecture. The target architecture must match an available architecture of the bootc-image-builder image you are using to build the disk image. Currently, amd64 and arm64 are included in quay.io/centos-bootc/bootc-image-builder manifest list. The architecture of the bootc OCI image and the bootc-image-builder image must match. For example, when building a non-native architecture bootc OCI image, say, building for x86_64 from an arm-based Mac, it is possible to run podman build with the --platform linux/amd64 flag. In this case, to then build a disk image from the same arm-based Mac, you should provide --target-arch amd64 when running the bootc-image-builder command.

☁️ Cloud uploaders

Amazon Machine Images (AMIs)

Prerequisites

In order to successfully import an AMI into your AWS account, you need to have the vmimport service role configured on your account.

Flags

AMIs can be automatically uploaded to AWS by specifying the following flags:

Argument	Description
--aws-ami-name	Name for the AMI in AWS
--aws-bucket	Target S3 bucket name for intermediate storage when creating AMI
--aws-region	Target region for AWS uploads

Notes:

These flags must all be specified together. If none are specified, the AMI is exported to the output directory.
The bucket must already exist in the selected region, bootc-image-builder will not create it if it is missing.
The output volume is not needed in this case. The image is uploaded to AWS and not exported.

AWS credentials file

If you already have a credentials file (usually in $HOME/.aws/credentials) you need to forward the directory to the container

For example:

 $ sudo podman run \
  --rm \
  -it \
  --privileged \
  --pull=newer \
  --security-opt label=type:unconfined_t \
  -v $HOME/.aws:/root/.aws:ro \
  --env AWS_PROFILE=default \
  quay.io/centos-bootc/bootc-image-builder:latest \
  --type ami \
  --aws-ami-name centos-bootc-ami \
  --aws-bucket fedora-bootc-bucket \
  --aws-region us-east-1 \
  quay.io/centos-bootc/centos-bootc:stream9

Notes:

you can also inject ALL your AWS configuration parameters with --env AWS_*

see the AWS CLI documentation for more information about other environment variables

AWS credentials via environment

AWS credentials can be specified through two environment variables:

Variable name	Description
AWS_ACCESS_KEY_ID	AWS access key associated with an IAM account.
AWS_SECRET_ACCESS_KEY	Specifies the secret key associated with the access key. This is essentially the "password" for the access key.

Those should not be specified with --env as plain value, but you can silently hand them over with --env AWS_* or save these variables in a file and pass them using the --env-file flag for podman run.

For example:

$ cat aws.secrets
AWS_ACCESS_KEY_ID=AKIAIOSFODNN7EXAMPLE
AWS_SECRET_ACCESS_KEY=wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY

$ sudo podman run \
  --rm \
  -it \
  --privileged \
  --pull=newer \
  --security-opt label=type:unconfined_t \
  --env-file=aws.secrets \
  quay.io/centos-bootc/bootc-image-builder:latest \
  --type ami \
  --aws-ami-name centos-bootc-ami \
  --aws-bucket centos-bootc-bucket \
  --aws-region us-east-1 \
  quay.io/centos-bootc/centos-bootc:stream9

💽 Volumes

The following volumes can be mounted inside the container:

Volume	Purpose	Required
`/output`	Used for storing the resulting artifacts	✅
`/store`	Used for the osbuild store	No
`/rpmmd`	Used for the DNF cache	No

📝 Build config

A build config is a Toml (or JSON) file with customizations for the resulting image. The config file is mapped into the container directory to /config.toml. The customizations are specified under a customizations object.

As an example, let's show how you can add a user to the image:

Firstly create a file ./config.toml and put the following content into it:

[[customizations.user]]
name = "alice"
password = "bob"
key = "ssh-rsa AAA ... [email protected]"
groups = ["wheel"]

Then, run bootc-image-builder with the following arguments:

sudo podman run \
    --rm \
    -it \
    --privileged \
    --pull=newer \
    --security-opt label=type:unconfined_t \
    -v ./config.toml:/config.toml:ro \
    -v ./output:/output \
    quay.io/centos-bootc/bootc-image-builder:latest \
    --type qcow2 \
    quay.io/centos-bootc/centos-bootc:stream9

The configuration can also be passed in via stdin when --config - is used. Only JSON configuration is supported in this mode.

Users (`user`, array)

Possible fields:

Field	Use	Required
`name`	Name of the user	✅
`password`	Unencrypted password	No
`key`	Public SSH key contents	No
`groups`	An array of secondary to put the user into	No

Example:

{
  "customizations": {
    "user": [
      {
        "name": "alice",
        "password": "bob",
        "key": "ssh-rsa AAA ... [email protected]",
        "groups": [
          "wheel",
          "admins"
        ]
      }
    ]
  }
}

Kernel Arguments (`kernel`, mapping)

{
  "customizations": {
    "kernel": {
      "append": "mitigations=auto,nosmt"
    }
  }
}

Filesystems (`filesystem`, array)

The filesystem section of the customizations can be used to set the minimum size of the base partitions (/ and /boot) as well as to create extra partitions with mountpoints under /var.

[[customizations.filesystem]]
mountpoint = "/"
minsize = "10 GiB"

[[customizations.filesystem]]
mountpoint = "/var/data"
minsize = "20 GiB"

{
  "customizations": {
    "filesystem": [
      {
        "mountpoint": "/",
        "minsize": "10 GiB"
      },
      {
        "mountpoint": "/var/data",
        "minsize": "20 GiB"
      }
    ]
  }
}

Interaction with `rootfs`

Filesystem types

The --rootfs option also sets the filesystem types for all additional mountpoints, where appropriate. See the see Detailed description of optional flags.

Allowed mountpoints and sizes

The following restrictions and rules apply, unless the rootfs is btrfs:

/ can be specified to set the desired (minimum) size of the root filesystem. The final size of the filesystem, mounted at /sysroot on a booted system, is the value specified in this configuration or 2x the size of the base container, whichever is largest.
/bootcan be specified to set the desired size of the boot partition.
Subdirectories of /var are supported, but symlinks in /var are not. For example, /var/home and /var/run are symlinks and cannot be filesystems on their own.
/var itself cannot be a mountpoint.

The rootfs option (or source container config, see Detailed description of optional flags section) defines the filesystem type for the root filesystem. Currently, creation of btrfs subvolumes at build time is not supported. Therefore, if the rootfs is btrfs, no custom mountpoints are supported under /var. Only / and /boot can be configured.

Anaconda ISO (installer) options (`installer`, mapping)

Users can include kickstart file content that will be added to an ISO build to configure the installation process. Since multi-line strings are difficult to write and read in json, it's easier to use the toml format when adding kickstart contents:

[customizations.installer.kickstart]
contents = """
text --non-interactive
zerombr
clearpart --all --initlabel --disklabel=gpt
autopart --noswap --type=lvm
network --bootproto=dhcp --device=link --activate --onboot=on
"""

The equivalent in json would be:

{
  "customizations": {
    "installer": {
      "kickstart": {
        "contents": "text --non-interactive\nzerombr\nclearpart --all --initlabel --disklabel=gpt\nautopart --noswap --type=lvm\nnetwork --bootproto=dhcp --device=link --activate --onboot=on"
      }
    }
  }
}

Note that bootc-image-builder will automatically add the command that installs the container image (ostreecontainer ...), so this line or any line that conflicts with it should not be included. See the relevant Kickstart documentation for more information. No other kickstart commands are added by bootc-image-builder in this case, so it is the responsibility of the user to provide all other commands (for example, for partitioning, network, language, etc).

Anaconda ISO (installer) Modules

The Anaconda installer can be configured by enabling or disabling its dbus modules.

[customizations.installer.modules]
enable = [
  "org.fedoraproject.Anaconda.Modules.Localization"
]
disable = [
  "org.fedoraproject.Anaconda.Modules.Users"
]

{
  "customizations": {
    "installer": {
      "modules": {
        "enable": [
          "org.fedoraproject.Anaconda.Modules.Localization"
        ],
        "disable": [
          "org.fedoraproject.Anaconda.Modules.Users"
        ]
      }
    }
  }
}

The following module names are known and supported:

org.fedoraproject.Anaconda.Modules.Localization
org.fedoraproject.Anaconda.Modules.Network
org.fedoraproject.Anaconda.Modules.Payloads
org.fedoraproject.Anaconda.Modules.Runtime
org.fedoraproject.Anaconda.Modules.Security
org.fedoraproject.Anaconda.Modules.Services
org.fedoraproject.Anaconda.Modules.Storage
org.fedoraproject.Anaconda.Modules.Subscription
org.fedoraproject.Anaconda.Modules.Timezone
org.fedoraproject.Anaconda.Modules.Users

Note: The values are not validated. Any name listed under enable will be added to the Anaconda configuration. This way, new or unknown modules can be enabled. However, it also means that mistyped or incorrect values may cause Anaconda to fail to start.

By default, the following modules are enabled for all Anaconda ISOs:

org.fedoraproject.Anaconda.Modules.Network
org.fedoraproject.Anaconda.Modules.Payloads
org.fedoraproject.Anaconda.Modules.Security
org.fedoraproject.Anaconda.Modules.Services
org.fedoraproject.Anaconda.Modules.Storage
org.fedoraproject.Anaconda.Modules.Users

Enable vs Disable priority

The disable list is processed after the enable list and therefore takes priority. In other words, adding the same module in both enable and disable will result in the module being disabled. Furthermore, adding a module that is enabled by default to disable will result in the module being disabled.

Building

To build the container locally you can run

sudo podman build --tag bootc-image-builder .

NOTE: running already the podman build as root avoids problems later as we need to run the building of the image as root anyway

Accessing the system

With a virtual machine launched with the above virt-install example, access the system with

ssh -i /path/to/private/ssh-key alice@ip-address

Note that if you do not provide a password for the provided user, sudo will not work unless passwordless sudo is configured. The base image quay.io/centos-bootc/centos-bootc:stream9 does not configure passwordless sudo. This can be configured in a derived bootc container by including the following in a Containerfile.

FROM quay.io/centos-bootc/centos-bootc:stream9
ADD wheel-passwordless-sudo /etc/sudoers.d/wheel-passwordless-sudo

The contents of the file wheel-passwordless-sudo should be

%wheel ALL=(ALL) NOPASSWD: ALL

Reporting bugs

Please report bugs to the Bug Tracker and include instructions to reproduce and the output of:

$ sudo podman run --rm -it quay.io/centos-bootc/bootc-image-builder:latest version

Contributing

Please refer to the developer guide to learn about our workflow, code style and more.

🗄️ Repository

web: https://github.com/osbuild/bootc-image-builder
https: https://github.com/osbuild/bootc-image-builder.git
ssh: [email protected]:osbuild/bootc-image-builder.git

📊 Project

Website: https://www.osbuild.org
Bug Tracker: https://github.com/osbuild/bootc-image-builder/issues
Matrix: #image-builder on fedoraproject.org

Discussions: https://github.com/orgs/osbuild/discussions

🧾 License

Apache-2.0
See LICENSE file for details.

Name		Name	Last commit message	Last commit date
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.fmf		.fmf
.github		.github
.tekton		.tekton
bib		bib
devel		devel
plans		plans
test		test
.dockerignore		.dockerignore
.gitignore		.gitignore
.gitleaks.toml		.gitleaks.toml
Containerfile		Containerfile
HACKING.md		HACKING.md
LICENSE		LICENSE
Makefile		Makefile
README.md		README.md
build.sh		build.sh
group_osbuild-osbuild-fedora.repo		group_osbuild-osbuild-fedora.repo
package-requires.txt		package-requires.txt
pytest.ini		pytest.ini

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osbuild/bootc-image-builder

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