The previous Tegra kernel metapackage implementation (linux-nvidia-tegra-igx)
was initially planned to apply both for Jetson devices and IGX systems. It turned
out recently (LP: #2069179) that we now need to reserve the metapackage name
linux-nvidia-tegra-igx for IGX systems, and use the new linux-nvidia-tegra-jetson
metapackage for Jetson devices. For the sake of clarity, the image name, model,
sub-arch, variant should align with the kernel metapackage name.
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.
The LXD snap is no longer seeded in any images since Noble+ so the LXD related unminimize logic in
./live-build/auto/build?h=ubuntu/noble and ./live-build/ubuntu-server/hooks/01-unminimize.chroot_early
is no longer required.
lxd-installer can remain installed.
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.
This has become moot now that the code block has been
moved out from live-build/functions to live-build/auto/build
so passing the argument is not needed anymore.
