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Using the commandline

An image is specified by a blueprint and an image type. Unless you specify otherwise, it will use the same distribution and version (e.g. Fedora 39) as the host system. The architecture will always be the same as the one on the host.

Blueprints management using composer-cli

osbuild-composer provides storage for blueprints. To store a blueprint.toml blueprint file, run this command:

$ composer-cli blueprints push blueprint.toml

To verify that the blueprint is available, list all currently stored blueprints:

$ composer-cli blueprints list

To display the blueprint you have just added, run the command:

$ sudo composer-cli blueprints show base-image-with-tmux
name = "base-image-with-tmux"
description = "A base system with tmux"
version = "0.0.1"
modules = []
groups = []

name = "tmux"
version = "*"

Building an image using composer-cli

To build a customized image, start by choosing the blueprint and image type you would like to build. To do so, run the following commands:

$ sudo composer-cli blueprints list
$ sudo composer-cli compose types

and trigger a compose (example using the blueprint from the previous section):

$ composer-cli compose start base-image-with-tmux qcow2
Compose ab71b61a-b3c4-434f-b214-1e16527766ff added to the queue

Note that the compose is assigned with a Universally Unique Identifier (UUID), that you can use to monitor the image build progress:

$ composer-cli compose info ab71b61a-b3c4-434f-b214-1e16527766ff
ab71b61a-b3c4-434f-b214-1e16527766ff RUNNING base-image-with-tmux 0.0.1 qcow2 2147483648

At this time, the compose is in a "RUNNING" state. Once the compose reaches the "FINISHED" state, you can download the resulting image by running the following command:

$ sudo composer-cli compose results ab71b61a-b3c4-434f-b214-1e16527766ff
ab71b61a-b3c4-434f-b214-1e16527766ff.tar: 455.18 MB
$ fd
$ tar xf ab71b61a-b3c4-434f-b214-1e16527766ff.tar
$ fd

From the example output above, the resulting tarball contains not only the qcow2 image, but also a JSON file, which is the osbuild manifest (see the Developer Guide for more details), and a directory with logs.

For more options, see the help text for composer-cli:

$ sudo composer-cli compose help

Tip: Booting the image with qemu

If you want to quickly run the resulting image, you can use qemu:

$ qemu-system-x86_64 \
-enable-kvm \
-m 3000 \
-snapshot \
-cpu host \
-net nic,model=virtio \
-net user,hostfwd=tcp::2223-:22 \

Be aware that you must specify a way to access the machine in the blueprint. For example, you can create a user with known password, set an SSH key, or enable cloud-init to use a cloud-init ISO file.