mkosi

mkosi stands for Make Operating System Image, and is a tool for generating an OS tree or image that can be booted.

Installation

Install mkosi or mkosi-git^AUR. Depending on what distribution you want to build install the following packages:

Distribution	Package
Arch	arch-install-scripts
Debian	debootstrap, debian-archive-keyring
Ubuntu	debootstrap, ubuntu-keyring
Fedora	dnf
OpenSUSE	zypper-git^AUR
CentOS	dnf-legacy-utils^AUR

Basic usage

You can create an image by just running it without any arguments:

# mkosi

You can specify option as arguments or by editing files in the current folder.

Create and boot a Debian image

The following command will create a bootable image with the latest Debian version and the package openssh-client installed:

$ mkosi -d debian -t gpt_ext4 -b --checksum --password password --package openssh-client,vim -o image.raw

systemd-nspawn can boot the resulting image:

# systemd-nspawn -b -i image.raw

It can also be virtualized with QEMU/KVM:

$ qemu-system-x86_64 -m 512 -smp 2 -bios /usr/share/ovmf/x64/OVMF_CODE.fd -drive format=raw,file=image.raw

You can also write this image to a USB drive and use it to boot your computer.

Using configuration files

The same image can be created by creating a configuration file:

mkosi.default

[Distribution]
Distribution=debian
Release=stretch

[Output]
Format=gpt_ext4
Bootable=yes
Output=image.raw

[Packages]
Packages=
         openssh-client
         vim

[Validation]
Password=password

Tip: If you create a folder mkosi.cache in current working directory, mkosi will save all downloaded packages there, so you can recreate images faster.

Configurations

Basic options can be specified as command-line arguments or in a file called mkosi.default in your current directory. Most important options:

Argument	Option in mkosi.default	Description
`-d`	[Distribution] Distribution=	The name of the distribution to install, e.g `arch`.
`-r`	[Distribution] Release=	The version of the distribution: jessie, 21, …
`-t`	[Output] Format=	Format of the image to create: gpt_ext4: Image file with GPT partition table and ext4 file system gpt_btrfs: Image file with GPT partition table and btrfs file system gpt_squashfs: Image file with GPT partition table and squashfs file system directory: A plain directory subvolume: A btrfs subvolume tar: A tar-ball of a plain directory
`-b`	[Output] Bootable=yes	Make the image bootable
`--root-size`	[Output] RootSize=	Size of the root file system
`-p`	[Packages] Packages=	List of packages to be installed into the image
`-o`	[Output] Output=	File/directory-Name
`--password`	[Validation] Password=password	Set the initial root password