Debian CD Image for AArch64 Laptops

The repository contains the Debian CD image releases for AArch64 Laptops. The CD image works on AArch64 laptops in the same way as what people usually see on X86 devices. This guide only highlights the quirks we need to deal with on AArch64 laptops. The CD image is tested on Lenovo Yoga C630 laptop with the following conditions.

• Secure Boot is disabled.
• The laptop has Windows 10 installed.
• BitLocker on Windows partition is turned off.

Installer limitations

After installation completes, you will get a fully functional kernel booting with device tree. But installer kernel boots up with ACPI and only provides a minimal support required by installation, like display via efifb, HID devices, USB and UFS.

• Wifi is not working for installer. While USB dongle could be used to get network support in installer, this guide assumes there is no network connection with the installation.

Installation tips

Although the installation is intuitive and Debian install guide could be found here, we would like to give a few tips you might find them useful.

• The installer is able to resize Windows partition, so that disk space could be freed up for Debian installation. Go for Manual option at Partition disks step, set up partitions for Debian installation. After all changes are made, scroll down the screen to select Finish partitioning and write changes to disk.

• As there is no network connection during the installation, Configure the package manager step should be skipped by selecting Go Back instead of Continue.

• The step Install the GRUB boot loader takes a couple of minutes to complete. Be patient.

AArch64 quirks

If everything goes fine, you will get Installation complete prompt in the end. However, it's not really completed yet for AArch64 devices, as we need to run UEFI Shell.efi for a couple of reasons.

• Linux efibootmgr utility doesn't work on AArch64 devices, because efivars doesn't work. The reason behind it is that EFI variables are stored on UFS, while firmware and OS cannot share the UFS device. Consequently EFI Boot variable cannot be modified to point to Grub, and device always directly boots into Windows. We need to use Shell.efi for EFI variable update.

• DtbLoader is used to load DTB using CHIDs. DtbLoader.elf and DTBs named in CHIDs have been installed to ESP partition as part of the Debian installation. But we need to additionally insert a command to UEFI, so that DtbLoader.efi will be run by UEFI for every power-on.

Follow the steps below to launch Shell.efi for completing installation.

1. From Debian Installation complete prompt, reboot with leaving USB disk plugged-in. Press 'c' in Grub menu to get 'grub> ' command-line prompt.

2. Launch Shell.efi that resides in USB disk like below.

grub> chainloader (hd0,msdos2)/efi/shell/Shell.efi
grub> boot

3. Identify the FS number of ESP partition on UFS by checking there is a grubaa64.efi in EFI\debian folder.

Shell> map -r -b
Shell> fs5:
FS5:\> ls EFI\debian

4. Modify variable Boot0001 to get it point to grubaa64.efi. The number 2 in the second command is identified by looking at Option field in the first command output.

FS5:\> bcfg boot dump
...
Option 02. Variable: Boot0001
  Desc   - Windows Boot Manager
...
FS5:\> bcfg boot modf 2 EFI\debian/grubaa64.efi

5. Tell UEFI to launch DtbLoader.efi for every boot.

FS5:\> bcfg driver add 1 DtbLoader.efi "dtb loader"

6. Now installation really completes. Remove the USB disk and reboot like below.

FS5:\> reset

Firmware installation

At this point, you should be able to boot up Debian and login Gnome desktop. However, some hardware blocks are not working properly yet because firmware is missing. Follow steps below to install firmware.

1. Add user to sudo group.

$ su - root
$ usermod -aG sudo <username>
$ exit
$ su - <username>

2. Run yoga_fw_extract.sh to retrieve firmware files that we cannot find in linux-firmware repository from Windows partition. This is a cut-down version of a script from the Celliwig project.

$ /lib/firmware/yoga_fw_extract.sh

3. Reboot the device.

Debian first-run

Here are a few things that you want to set up to get the best experience.

1. Go to Settings and set up Wi-Fi to get a network connection.

2. Update /etc/apt/sources.list with the best Debian mirror per your location, drop sid-security repository which doesn't have a Release file.

$ cat /etc/apt/sources.list
deb http://deb.debian.org/debian sid main
deb-src http://deb.debian.org/debian sid main
$ sudo apt update

3. Install alsa-ucm-conf from Linaro OBS to enable audio.

$ sudo apt install alsa-ucm-conf=1.2.3-1+linaro3
$ pulseaudio -k

Misc tips

• The default GNOME login is backed by Wayland. If you want to use login backed by Xorg like System X11 Default, GNOME Classic or GNOME on Xorg, package xinit needs to be installed.

$ sudo apt install xinit

• By default, only left button on touchpad works. Goto Settings -> Mouse & Touchpad -> Touchpad and turn on option Tap to Click, so that you will get one-finger tap as left click and two-fingers tap as right click.