Uploaded to Jammy, pending normal SRU processing.
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https://bugs.launchpad.net/bugs/1981385
Title:
initrd lacks modules to mount boot image from http boot
Status in initramfs-tools package in Ubuntu:
Fix Released
Status in initramfs-tools source package in Jammy:
In Progress
Bug description:
[ Impact ]
* If you use UEFI http boot to boot an image (rather than an EFI
executable) and get all the way to a normal userspace, you can
access the boot image as /dev/pmem0. But this is not accessible in
the initrd; presumably some modules are missing.
* This is desirable because then you can just feed an installer ISO to
a machine via http boot and the installer just works as normal
* Add support for physical pmem devices, and simulation thereof with
the memmap kernel command line parameter
* The initrd is larger
[ Test Plan ]
* unpack an initrd on a Jammy system with the generic kernel
metapackage with unmkinitramfs
* observe that the directories kernel/drivers/{nvdimm,dax,acpi/nfit}
are not present
* install the updated initramfs-tools packages from proposed
* again unpack an initrd on a Jammy system with the generic kernel
metapackage with unmkinitramfs
* observe that the directories kernel/drivers/{nvdimm,dax,acpi/nfit}
are present now
* reboot to confirm that the system still boots
* modify /etc/default/grub GRUB_CMDLINE_LINUX_DEFAULT to contain a
memmap entry - memmap=1G!4G seems to work on many systems over 4G of
RAM, or do `dmesg | grep BIOS-e820` to observe the memory regions
and select a usable one.
* update-grub and reboot again
* a /dev/pmem device should now be present on the system
[ Where problems could occur ]
* The growth of the files in /boot will accelerate issues for users
who have a dedicated boot partition that is not large enough
[ Other Info ]
* Details on the memmap kernel command line parameter:
https://www.kernel.org/doc/Documentation/admin-guide/kernel-parameters.txt
* PMEM simulation with memmap:
https://docs.pmem.io/persistent-memory/getting-started-guide/creating-development-environments/linux-environments/linux-memmap
[ Original Bug Description ]
If you use UEFI http boot to boot an image (rather than an EFI
executable) and get all the way to a normal userspace, you can access
the boot image as /dev/pmem0. But this is not accessible in the
initrd; presumably some modules are missing. Dimitri added some
modules that are clearly going to be necessary (kernel/drivers/nvdimm)
in 0.140ubuntu14 and I added kernel/drivers/dax too in local
experiments but this appears not to be enough to get it to appear.
This is desirable because then you can just feed an installer ISO to a
machine via http boot and the installer just works as normal (the
speed and, uh, quality, of the implementation of HTTP in a given
machine's firmware may mean this isn't always the best option but it
would be nice if it worked in case someone's machine actually does
this well).
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