Problem when logging in and out

I have recently (the other day) reinstalled a fresh copy of UM 16.04 LTS 64 bit.

However, a novel issue has arisen.

When the system is booting up, just prior to the login screen, it locks up. However, if I switch off my monitor, the boot-up/login resumes. If I wait a few seconds and then switch the monitor back on, it is at the login screen and I am able to enter my password and click the login button. But, it then completely freezes again. Once more, if I switch off the monitor, the login will resume and when I switch the monitor back on again, I am now in the session and all works as it should.

But, when I go to log out, I have the same problem in reverse, more or less. That is to say, after invoking the logout, the screen drops to the usual console and displays the logging off processes, but then locks up a fews seconds in. The only way to unlock it is to switch off the monitor, at which point the logging off will complete.

I have never experienced this problem before and so am very interested as to what is causing it.

I am guessing it is a GPU/monitor issue and so, for clarity, the GPU I am using is Radeon R7 200 and the “monitor” I am using is actually a bog standard supermarket LCD TV with an HDMI input

I should also note, this issue was not present when I first installed. However, since then, I have installed the Ubuntu studio meta package and have implemented all updates/upgrades. Somewhere in that process is when the problem began. But, I cannot say precisely where.

Any advice/help gratefully received.

Just thinking outloud…

It sure sounds like graphics but I was looking at what ubuntustudio-desktop adds. A Plymouth theme caught my eye. That is consistent with up AND down but not login to the desktop.

What happens with a Console Mode boot?

I wonder if systemd-analyze blame might provide a direction. If it hangs everything, then everything may just show high times making it useless.

The latest ISO, and this is relatively new to this LTS, uses the hwe (Hardware Enablement) kernel so the LTS tries to keep up on new hardware but I’m not convinced it solves more problems than it causes. You probably have the 4.10 kernel while an original ISO uses 4.4. You could test the 4.4 kernel.

EDIT: I just tried a VM installed with 16.04.3 ISO (4.10 kernel). One meta package linux-generic pulls in the entre 4.4 kernel but you have to explicitely select it in grub. I didn’t see where UbuntuStudio installs real-time or low-latency kernels - thought it did.

Yes, it installs the low latency kernel. Which is what I am now running on since installing the Ubuntu Studio metapackage.

4.4.0-93-lowlatency, to be precise.

Also, I didn’t install the desktop, just the audio, graphics and video packages and the low latency kernel:


sudo apt-get update && sudo apt-get upgrade && sudo apt-get install linux-lowlatency && sudo apt-get update && sudo apt-get upgrade && sudo apt-get install ubuntustudio-audio ubuntustudio-audio-plugins ubuntustudio-graphics ubuntustudio-video

Is the older kernel still available to try?

I’ll have a check and get back


The low latency kernel is the culprit. I am now running on:


And the problem has vanished.

Ultimately, it’s probably the kernel and graphics combo. Changing either is a new roll of the dice.

Well, I am stuck with the GPU driver as it is the open source one because AMD have stopped producing a propriety one

So, changing kernel is my only option

The thing is, I have been using that version of the low latency kernel right up to the reinstall. I have a strong suspicion that some upgrades that are present in newer kernels are are pushed back as rolling “updates” to old kernels sitting in the repos so that they cannot be relied upon to remain as they were when reinstalled.

Are you using the AMD proprietary driver? If you are, it might be worth trying this:

  • Use the “normal” kernel and revert back to the open source driver, reboot.
  • Install the low latency kernel, this will rule out the open source drivers breaking.
  • If it works, try installing the AMD driver. This should build/install it against the kernel it’s running.

Edit: Ahh sorry, post sent at the same time. I forgot about the situation with older AMD cards and newer Ubuntu versions, particularly Xorg.

There is no AMD driver now. There hasn’t been for over a couple of years. Or, have a I got that wrong?

In any event, it is the open source driver that is in use and so this is what has been running against both the generic and low latency kernel

A few more rolls of the dice. These meta packages are for the lowlatency kernel:


They are for 4.10 and 4.11 (bleeding edge as it gets in 16.04 repository)

EDIT: Just FYI, removing the meta packages, I think, allows autoremove to cleanly get rid of them. But later kernel numbers I’m not sure if it works.

Both the 4.4.0-93-lowlatency and the 4.4.0-92-lowlatency kernels are giving the same problem. But, I am absolutely certain that I was using at least the 4.4.0-92-lowlatency kernel prior to the reinstall of the system. So, as I mentioned earlier, I am convinced that certain aspects of new kernels are somehow sometimes sent backwards to old kernels as updates/upgrades. Which, is actually really irritating because it means there can be no certainty.

Anyway, I am going to do a bit more testing and will report back.