By placing the kernel in minimal, we can achieve the following
improvements:
1. Space savings - there are redundant packages present in the ship-live
pool and in the live layer. Adding the kernel to minimal means that
the kernel is already in the live layer, and we don't then also need
it in the pool.
2. Time savings - informal vm testing suggests more than a minute
improvement to have the kernel preinstalled over installing it at
runtime.
As always, there is a cost tradeoff:
1. If a different kernel is desired, we need to be able to remove this
preinstalled kernel. Relevant curtin and subiquity changes are
already landed.
2. When installing that other kernel, it'll take longer than today due
to still needing to install a kernel at runtime + the time cost of
removing the preinstalled kernel.
Ubuntu Studio wants to add a minimal installation. The individual tasks
are metapackages that can be installed by the ubuntustudio-desktop task.
With that in mind, we would like to reintroduce
ubuntustudio-desktop-core as a minimal installation. This is made much
easier with the layered images compared to the package removal format
used by ubiquity. This also means ubuntustudio-desktop-core becomes the
base seed.
If I'm missing anything, please advise.
The lowlatency kernel will eventually undergo deprecation. Rather than
wait for such a time to happen and be reactive, Ubuntu Studio would
rather be proactive about this now that the generic kernel can act as a
lowlatency kernel with certain command line parameters as outlined by
https://discourse.ubuntu.com/t/fine-tuning-the-ubuntu-24-04-kernel-for-low-latency-throughput-and-power-efficiency/44834.
As such, we have modified our `ubuntustudio-lowlatency-settings`
package, which installs `/etc/default/grub.d/ubuntustudio.cfg` with the
following line:
-GRUB_CMDLINE_LINUX_DEFAULT="$GRUB_CMDLINE_LINUX_DEFAULT threadirqs"
+GRUB_CMDLINE_LINUX_DEFAULT="$GRUB_CMDLINE_LINUX_DEFAULT preempt=full
nohz_full=all threadirqs"
Additionally, that same file used to set "GRUB_FLAVOUR_ORDER" which is
no longer needed.
The ubuntu-core-installer image is an installer that installs ubuntu
core. The environment the installer runs in is similar to the server
installer but it has a source catalog entry that points to the model
created in ubuntu-core-installer/hooks/05-prepare-image.binary, which
subiquity knows how to install.
do_layered_desktop_image() is now the standard entry point for flavors using
ubuntu-desktop-bootstrap and handles minimal/standard/live layers in a
configurable and flavor-agnostic way to reduce code duplication.
ubuntu/include.* are the master location for these files.
Copy them over for projects with similar needs, while skipping ones that
are incorrect.
LP: #2055077
Ubuntu MATE is switching to a layered image in preparation to
use ubuntu-desktop-provision. Luckily, their seed structure is
already well-structured for layering, so this is easily done.
Per the comments, BASE_SEED was initially used to identify the seed in the
flavor to use for identifying preseeded snaps, and later was also used to
identify which "minimal-remove" seed to apply to an image.
The first usage is now obsolete after a refactor; we now correctly detect
snaps from any of the included seeds without needing an explicit
declaration.
The second usage only applies to installer images that are NOT using layered
squashfs, since for these images 'minimal' is a separate squashfs layer
rather than a list of packages to remove after the fact.
Refactor this code to eliminate pointless definitions of BASE_SEED and
define it only for the subset of flavors today that:
- have a 'minimal-remove' seed
- are not using layered squashfs.
Dan Bungert
Sergio Costas Rodriguez
Steve Langasek
Heinrich Schuchardt
Erich Eickmeyer
Zhai Zhaoxuan
Michael Hudson-Doyle
Łukasz 'sil2100' Zemczak
Aaron Rainbolt
Simon Quigley
Sebastien Bacher
handsome_feng
Sean Davis