Testing and signing kernel for Ubuntu 20.04

Fri, 15 May 2020 10:04:54 +0100

Disclaimer. This is about mainline kernel builds, summarized from the Ubuntu wiki:

By default, Ubuntu systems run with the Ubuntu kernels provided by the Ubuntu repositories. However it is handy to test unmodified upstream kernels to help locate problems in Ubuntu kernel patches, or to confirm that upstream has fixed a specific issue. These kernels are not supported and are not appropriate for production use.

Install a mainline kernel via PPA

Detailed official instructions: https://wiki.ubuntu.com/Kernel/MainlineBuilds.

There is a semi-automated wrapper that makes this much less painful: https://github.com/pimlie/ubuntu-mainline-kernel.sh

Install an RC release

sudo ubuntu-mainline-kernel.sh --rc -i

MOK keys (Secure Boot)

If you installed Ubuntu 20.04 with Secure Boot enabled and chose to install third-party drivers, you were probably asked to enroll a new key in MOK. That key is then used to sign new kernel modules automatically. It lives at:

$ ls /var/lib/shim-signed/mok/
MOK.der MOK.priv

To sign the kernel itself you need the key in PEM form:

$ cd /var/lib/shim-signed/mok
$ sudo openssl x509 -in MOK.der -inform DER -outform PEM -out MOK.pem

Sign the kernel

Sign the vmlinuz of your choice:

sudo sbsign --key /var/lib/shim-signed/mok/MOK.priv \
 --cert /var/lib/shim-signed/mok/MOK.pem \
 /boot/vmlinuz-[KERNEL-VERSION]-generic \
 --output /boot/vmlinuz-[KERNEL-VERSION]-generic.signed

Copy the initrd so it pairs with the signed vmlinuz:

sudo cp /boot/initrd.img-[KERNEL-VERSION]-generic{,.signed}

Update GRUB:
```
sudo update-grub
```

Reboot and test

Pick the .signed entry in GRUB. If the system boots cleanly and you want to keep the configuration, overwrite the unsigned files with the signed ones and run update-grub again:

sudo mv /boot/vmlinuz-[KERNEL-VERSION]-generic{.signed,}
sudo mv /boot/initrd.img-[KERNEL-VERSION]-generic{.signed,}
sudo update-grub

Enable Mozilla Firefox and Thunderbird on Wayland in Ubuntu 20.04

Fri, 01 May 2020 10:04:54 +0100

This guide walks through turning on Wayland fractional scaling (FS) on Ubuntu 20.04 and then pointing Firefox and Thunderbird at it natively.

Wayland

At the time of writing Ubuntu counted Wayland users as “less than 1%”¹. Feel special.

Enable

Follow https://linuxconfig.org/how-to-enable-disable-wayland-on-ubuntu-20-04-desktop.

Test

GUI. Settings -> About -> Windowing system.

CLI. Check whether your current session is a Wayland one²:

# Check your session ID
$ loginctl
$ loginctl show-session <SESSION_ID> -p Type

# or as a one-liner
$ loginctl show-session $(awk '/tty/ {print $1}' <(loginctl)) -p Type | awk -F= '{print $2}'

For example:

$ loginctl
SESSION UID USER SEAT TTY
 12 1000 user seat0 tty2

1 sessions listed.

$ loginctl show-session 12 -p Type
Type=wayland

Fractional scaling

To enable Wayland FS:

$ gsettings set org.gnome.mutter experimental-features \
 "['scale-monitor-framebuffer', 'x11-randr-fractional-scaling']"

Log out and back in (or reboot). Displays -> Scaling now offers 100%, 125%, 150%, 175%, and 200%.

Firefox and Thunderbird on Wayland

Test it once

Firefox opens in X11 mode by default, which makes fonts blurry under fractional scaling. Run it once in Wayland mode:

$ MOZ_ENABLE_WAYLAND=1 firefox

Verify

Open about:support and check Window protocol under Graphics / Features. It reads x11 under XWayland and wayland as a native Wayland client³.

Make it the default

Copy the .desktop file into your user directory and patch it:

$ cp /usr/share/applications/firefox.desktop ~/.local/share/applications/firefox.desktop
$ sed -i 's/Exec=firefox/Exec=env MOZ_ENABLE_WAYLAND=1 firefox/g' \
 ~/.local/share/applications/firefox.desktop

Same drill for Thunderbird:

$ MOZ_ENABLE_WAYLAND=1 thunderbird
$ cp /usr/share/applications/thunderbird.desktop ~/.local/share/applications/thunderbird.desktop
$ sed -i 's/Exec=thunderbird/Exec=env MOZ_ENABLE_WAYLAND=1 thunderbird/g' \
 ~/.local/share/applications/thunderbird.desktop

Debugging a `.desktop` file

$ sudo apt install dex
$ dex ~/.local/share/applications/firefox.desktop

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