DisplayLink and ZFS on Ubuntu = Recovery Console (a work-around)

Today I filed an issue on the DisplayLink/EVDI Github Repository.

I recently obtained a new laptop, so installed Ubuntu with the encrypted ZFS root filesystem. This all works great! I then installed the DisplayLink drivers using the system recommended by Synaptics;

wget https://www.synaptics.com/sites/default/files/Ubuntu/pool/stable/main/all/synaptics-repository-keyring.deb
sudo apt install ./Downloads/synaptics-repository-keyring.deb
sudo apt update
sudo apt install displaylink-driver

At which point I’m prompted to reboot my system. All good, so far.

Except, what I’m presented with is a recovery console, asking me to enter my root password!

Fortunately, I’d had the common sense to set the password for my root account (sudo passwdwill do it), so I could sign in and start to figure out what was going on.

In my logs, I looked for anything to do with “displaylink”, and found this line:

Apr 28 11:13:05 jonspriggs-Kratos-EL04R6 systemd-udevd[1912]: 4-3.1.3:1.0: Spawned process '/opt/displaylink/udev.sh /dev /devices/pci0000:00/0000:00:14.0/usb4/4-3/4-3.1/4-3.1.3/4-3.1.3:1.0 usb-004-004-DisplayLink_PR09_DisplayPort_Dock_YVFJ093338 /dev/bus/usb/004/004' [2280] is taking longer than 59s to complete

Just after, it showed this log:

Apr 28 11:14:05 jonspriggs-Kratos-EL04R6 systemd[1]: systemd-udev-settle.service: Main process exited, code=exited, status=1/FAILURE
░░ Subject: Unit process exited
░░ Defined-By: systemd
░░ Support: http://www.ubuntu.com/support
░░ 
░░ An ExecStart= process belonging to unit systemd-udev-settle.service has exited.
░░ 
░░ The process' exit code is 'exited' and its exit status is 1.

So, my initial response was to purge the displaylink-driver (which I did, and it worked), but I actually quite like this dock, so I re-installed the driver and took a look at what else was in there.

Between the systemd-udev-settle.service starting and finishing with an error was this log entry:

Apr 28 11:12:05 jonspriggs-Kratos-EL04R6 udevadm[1890]: systemd-udev-settle.service is deprecated. Please fix zfs-load-module.service, zfs-import-cache.service not to pull it in.

Hmm, I wonder if that’s what the issue is?! So, I edited zfs-load-module.service (/lib/systemd/system/zfs-load-module.service) and zfs-import-cache.service (/lib/systemd/system/zfs-import-cache.service) files commenting out the line: Requires=systemd-udev-settle.serviceand restarted.

The system booted straight up! Huzzah!

I’ve had a look in the logs, and prior to installing the DisplayLink driver, I was getting this error above, but as systemd-udev-settle wasn’t failing to start, it wasn’t preventing zfs from loading, which in turn was preventing the boot, so the issue is definitely somewhere between DisplayLink and systemd-udev-settle, but we’ll see what happens as a result of this issue.