Title: Dracut changed default for hostonly setting
Author: Nowa Ammerlaan <nowa@gentoo.org>
Posted: 2025-02-03
Revision: 1
News-Item-Format: 2.0
Display-If-Installed: sys-kernel/installkernel[dracut]

Dracut is an initramfs generation tool. It may be invoked via the
installkernel mechanism in order to automatically generate a new
initramfs when the kernel is installed. If you are reading this then
sys-kernel/installkernel is configured to use Dracut and the below is
relevant for you.

What changed?
====================

Starting with version 106 of sys-kernel/dracut the default for the
"hostonly" setting has changed from disabled to enabled when Dracut is
invoked via installkernel[1].

"hostonly" is a setting for Dracut that controls how much is included
in the generated initramfs image. When it is disabled Dracut aims to
generate an initramfs image that is bootable on any hardware. On the
other hand, when this setting is enabled, Dracut aims to generate an
initramfs image containing only what is needed to boot the current
system. The advantage is a significantly smaller initramfs images,
but this comes with the cost of losing portability.

Example: When the "hostonly" setting is disabled, Dracut's drm module
will cause all GPU drivers to be included in the initramfs. When it is
enabled, only the drivers for GPUs that are currently present in the
system are included in the initramfs.

Enabling the "hostonly" setting was and is our recommendation for most
use cases. This however was not the default behaviour in versions
prior to 106.

Note, the default value for the "hostonly" setting has changed only
when Dracut is invoked via installkernel. Disabled remains the default
behaviour when Dracut is invoked directly.

User Action Required
====================

If your system is already configured to enable "hostonly" setting via
/etc/dracut.conf.d/ then effectively nothing has changed for you.

However, if Dracut has previously not been configured to enable the
"hostonly" setting, then starting with version 106 the behaviour of
Dracut will change for you. Though we do not expect major problems, we
recommend ensuring a backup booting option remains available before
rebooting the system after the first kernel upgrade following the
upgrade of Dracut. This is usually the case unless the old kernels are
manually removed by the user.

If you do experience a booting problem with the "hostonly" enabled
initramfs images, then please report this problem to Dracut[2].

The "hostonly" setting may be disabled via /etc/dracut.conf.d/
configuration snippets. For example:

	echo "hostonly=no" >> /etc/dracut.conf.d/95-no-hostonly.conf


[1] https://github.com/dracut-ng/dracut-ng/pull/1158
[2] https://github.com/dracut-ng/dracut-ng/issues