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I have a headless Raspberry Pi 4 (4GB) running 64-bit Ubuntu Server as my home NAS server. It drives 4 x 2TB USB3 drives in a ZFS RAIDZ, connected via a USB3 hub that also powers the Pi.

It has been running since about May, and has got noticeably more stable as 20.04 on the 64-bit Pi has matured. The only small gotcha I have noticed is that there are no precompiled ZFS binaries and the machine rebuilds all the ZFS modules every time I get a new kernel version.

I would like to install the HWE stack for 20.04.2 on the machine and thereby get kernel 5.8. However there do not seem to be any RasPi kernel packages. Is that right? The generic ARM HWE kernel does not work; it installs fine but the Pi simply reboots into the latest 5.4 kernel.

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  • I don't have a Pi available to test, but does sudo apt install linux-generic-hwe-20.04 work?
    – KGIII
    Mar 2, 2021 at 16:45
  • No, it doesn't. The Raspberry Pi does not use GRUB. The machine is headless so I cannot see any boot menu there may be. Mar 3, 2021 at 11:39
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    Pardon my brevity; I was on my phone. All RasPis boot by the GPU firmware loading files from a FAT32 partition on the SD card (although they can boot from USB or the network in recent models). There's no need for a bootloader so most distros don't use one. I tried installing the standard ARM64 HWE kernel with that command, but although it was installed, it wasn't added to the FAT32 partition (in /boot/firmware/) and the machine just rebooted into the standard kernel 5.4. Apparently Ubuntu on Pis uses a special, tweaked kernel with Pi support. Mar 3, 2021 at 13:57

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Your kernel name should ends with -raspi (run grep -A 7 "Raspberry Pi 4" /usr/share/flash-kernel/db/all.db and look at Kernel-Flavors: values), but linux-generic-hwe-20.04 depends on linux-image-*-generic or linux-image-*-generic-64k or any. So, you need to add two lines to /etc/flash-kernel/db before installing the new kernel:

Machine: Raspberry Pi 4 Model B Rev 1.1
Kernel-Flavors: raspi raspi2 64k generic-64k generic

Where Raspberry Pi 4 Model B Rev 1.1 is an output of cat /proc/device-tree/model ; echo and raspi raspi2 64k generic-64k generic is probable suffixes of the HWE kernel.

See also Raspberry Pi 4 custom kernel will not install in Ubuntu 19.10

PS: It works with kernel 5.8, but with 5.11 my raspberry had become unbootable.

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