How to use the command 'mkosi' (with examples)

The mkosi command is a tool for building modern, legacy-free Linux images. It is a part of systemd and can be used to create customized Linux images for various distributions. This article provides examples of different use cases of the mkosi command.

Use case 1: Show current build configuration to verify what would be built

Code:

mkosi summary

Motivation: The mkosi summary command allows users to check the current build configuration before actually building the image. This helps to ensure that the desired customizations and settings are correctly applied.

Explanation: This command displays the current build configuration, including the selected distribution, version, and any additional customizations. It provides a summary of what would be built if the mkosi build command is executed.

Example output:

Distribution: fedora-33
Distribution version: 33
Hostname: localhost
Image size: 2.1GB
Additional customizations: None

Use case 2: Build an image with default settings

Code:

mkosi build --distribution fedora

Motivation: The mkosi build command is used to create a Linux image with default settings. Users can specify the desired distribution using the --distribution argument. This allows for the creation of customized Linux images based on different distributions.

Explanation: This command builds a Linux image using the specified distribution. By default, it uses the distribution of the host system if no distribution is selected. In this example, the image will be built using Fedora.

Example output:

Building image using distribution: fedora
...
Image successfully built. Image file: fedora.img

Use case 3: Build an image and run an interactive shell in a systemd-nspawn container

Code:

mkosi shell

Motivation: The mkosi shell command allows users to build a Linux image and then directly access an interactive shell within a systemd-nspawn container. This provides a convenient way to test and interact with the image before deployment.

Explanation: This command builds a Linux image using the default settings and then launches an interactive shell within a systemd-nspawn container. Users can explore the image, install additional packages, configure settings, and perform various tasks.

Example output:

Building image...
...
Launching shell in systemd-nspawn container...
Welcome to the shell within the container!

Use case 4: Boot an image in a virtual machine using QEMU

Code:

mkosi qemu

Motivation: The mkosi qemu command enables users to boot a Linux image in a virtual machine using QEMU. This allows for testing and validating the image in an isolated environment.

Explanation: This command requires a disk image or a CPIO image with a provided kernel. It boots the image in a virtual machine using QEMU. Users can interact with the virtual machine and test the functionality and performance of the image.

Example output:

Booting image in QEMU...
...
Virtual machine successfully started. Ready for interaction.

Use case 5: Display help

Code:

mkosi help

Motivation: The mkosi help command provides users with a quick reference to the available commands and options of the mkosi tool. It helps users understand the usage and functionality of the command without referring to external sources.

Explanation: This command displays the help information for the mkosi command, including a list of available commands, their syntax, and the available options.

Example output:

Usage: mkosi [OPTIONS] COMMAND [ARGS]...

Options:
  --version   Show the version and exit.
  -h, --help  Show this message and exit.

Commands:
  build    Build a Linux image.
  qemu     Boot an image in a QEMU virtual machine.
  shell    Run an interactive shell in a systemd-nspawn...
  summary  Show current build configuration.

Conclusion:

The mkosi command is a powerful tool for building modern, legacy-free Linux images. It provides various options to customize the image and allows for testing and validation through interactive shells and virtual machines. By understanding the different use cases of the mkosi command, users can leverage its capabilities to create and deploy customized Linux images efficiently.