This repository hosts mkosi configuration files intended for kernel development using mkosi. By default, a an image is built which is booted with qemu's direct kernel boot and VirtioFS.

To get started, write the distribution you want to build to mkosi.local.conf in the root of the repository in the Distribution section. Currently CentOS, Fedora and Debian are supported. For example, for fedora, write the following:

[Distribution]
Distribution=fedora

Then, to build the image and boot it, run the following:

$ mkosi -f qemu

To exit qemu, press ctrl+a followed by c to enter the qemu monitor, and then type quit to exit the VM. Alternatively, run systemctl poweroff.

To build your own kernel, add the following to mkosi.conf:

[Config]
@Include=modules/kernel

[Content]
BuildSources=<path-to-your-kernel-sources>:kernel

If you want to mount a directory into the qemu VM, you can add the following:

[Host]
RuntimeTrees=<path-to-sources>:/path/in/guest

Now run mkosi -f qemu again and a custom kernel will be built and booted instead of the default one. The kconfig file will be picked up from the kernel source tree at mkosi.kernel.config. If it does not exist and the $CONFIG environment variable (set using Environment=) is not set, the default config file shipped with this repository (mkosi.kernel.config) is used instead. Alternatively, --config (or -c) can be used to pass the config path to use via the command line (e.g. mkosi -f build -c <path-to-config>).

To build the selftests, set SELFTESTS=1 using Environment=. SELFTESTS_TARGETS= can be used to only build specific selftests targets. SELFTESTS_SKIP_TARGETS= can be used to skip specific selftests targets, such as bpf which can take a long time to rebuild.

For each kernel, the out-of-tree build subdirectory used is synthesized from the localversion files in the given kernel source tree, the CONFIG_LOCALVERSION setting in the configuration and the $LOCALVERSION environment variable.

Various other modules are supported as well. For example, to use the btrfs-progs module to bulid and install btrfs-progs:

[Config]
@Include=modules/btrfs-progs

[Content]
BuildSources=<path-to-your-btrfs-progs-sources>:btrfs-progs

The same applies to the other modules (fstests, ltp, blktests, bpfilter).

To enable multiple modules, you can do the following:

[Config]
@Include=modules/btrfs-progs
         modules/kernel

[Content]
BuildSources=<path-to-your-btrfs-progs-sources>:btrfs-progs
             <path-to-your-kernel-sources>:kernel

To temporarily disable building a specific module, you can simply comment out the relevant BuildSources= entry without disabling the module itself.

This configuration will download the required tools to build and boot the image on the fly. To use this configuration, the following tools have to be installed:

• mkosi v19
• python 3.9 (Set $MKOSI_INTERPRETER to point to an alternative interpreter)
• bubblewrap
• package manager of the distribution you're building
• coreutils
• util-linux

All package and kconfig lists must be sorted using sort -u.