On shutdown screen fills with print and computer will not shut down.
 

My wife's Dell Inspiron laptop, running Ubuntu 16.04LTS has just developed this habit. When we attempt to shut down, instead of the doing what it should (and used to until recently) the screen fills with print and the shutdown process freezes. The only way that we manage to get the computer to shut down is to hold down the power switch until the screen goes blank, which is probably not a good solution in the long term.
Here is a photo of the screen, in case there are some clues to be found.
How can we get it back to normal?

Try shutting down from the terminal once, there are several commands that should work: sudo halt and sudo shutdown -h now

It's hard to read the picture on my device.

^ try that.

i can make out "watchdog/3 tainted".

it is difficult to say what is going on without additional information:

• did something occur prior to this? like, installing obscure software?
• has the system been kept updated/graded?
• are there any other problems with the hard/software?

btw, for the time being you can just continue shutdown normally, then long press the power button as described.
i don't think any (more) harm will come from it.

I tried both Mill J's suggestions. Thanks for them, but neither worked. I got the same screenful.
I did install libdvd-pkg but that's not terribly obscure and I have it on my own laptop which shuts down OK. Some of the keyboard shortcuts don't work as they should, but that has been true for some time, with the computer shutting down OK. The libdvd-pkg installation is on the suspect list.
Would a higher-res screen photo help? I scaled down the original photo to make the file smaller.

PS I did try a complete uninstall of libdvd-pkg but that didn't help.

That's a kernel oops - basically a segfault in the kernel. Never good.
Open a launchpad bug against Ubuntu - the devs will be able to determine if it needs to be pushed upstream. They will also be able to tell how to collect needed messages.

I am tempted to:
1. Make a good backup (never a bad idea, though there is a quite recent one).
and then
2. Immediately do a fresh installation of Ubuntu 16.04.
Is that likely to put things right? I had hoped that it would be a matter of just running some clever command or program. Going back to square 1 seems like an admission of failure, but why not admit the truth?

It probably began doing the oops after some sort of upgrade. If you report the problem to the Ubuntu launchpad, they will fix it. It's not something 'you're' going to fix. And, if you0 wait long enough, it might shut down even with the oops.

If all else fails then yes. But I encourage you to file a bug report as suggested by several others, it's not only for your good, but for the whole community. Especially since is sounds like it boots ok.

And no it's not admitting failure to reinstall when things go wrong(This is your way of Winning).

Keep us updated!

In the end I went ahead and reinstalled, and it works. Thanks for all the encouragement. Yes, it's my way of Winning. We call it creative failure.
I will try and remember how to report a bug. I have done one before.

you might want to do some web searches against exact laptop model + ubuntu + significant excerpt from error log.
you should be able to get at the error description with systemd's 'journalctl' command.

PS:
i spent 3 months in Dorking as an exchange pupil, went to school there.
Snooker in the crypt, Elephant beer in the park.
I even had a job in a restaurant doing the dishes. A coworker who was equally low on the hierarchy sang "Margaret Thatcher is a Lesbian" while cleaning the floors...
fond memories.