Bug#902185:

[Kyle Edwards]

On 06/26/2018 04:45 PM, Christopher Obbard wrote:
> A reinstall of Debian on my main PC seemed to fix it.

I was able to fix it by booting into a recovery shell and running:

$ apt-get install systemd

which updates systemd to the latest version. I then ran

$ apt-get install

to finish reconfiguring udev.

YMMV.

> My laptop boots to the WM but with no keyboard/mouse.

This is because udev is failing to start. A text-based recovery console 
will still work, and udev will work properly again once systemd is fully 
upgraded.

> This is a grave bug.

Agreed.