(X)ubuntu 22.04 boots to flashing cursor after PSU failure - unless Recovery Mode is selected

Question

This PC is Ubuntu Studio but with Xfce installed. Recently the PSU blew, causing power to arc across the room. But having replaced this part I'm able to log in normally - provided I go into Recovery Mode first.

If I leave it to boot normally, I get a flashing cursor. There are other posts about that problem (e.g. Ubuntu 20.04 boots to black screen with flashing cursor) but I believe this is slightly different. At the flashing cursor if I press Ctrl+Alt+F1 I can get to the terminal and log in BUT after an apparently-random time interval of a few seconds I am returned to the flashing cursor unless I press Ctrl+Alt+F1 again. I thought this suggested a hardware problem with the graphics card but when I do get Xfce started (see below) it no longer happens.

I have tried some of the top-rated fixes such as purging the proprietary nvidia drivers, adding nomodeset to grub, and commenting out additional and network disk drives from fstab.

If I try to do 'startx' from terminal under these circumstances it gives an error that:-

xinit: giving up xinit: unable to connect to x server: connection refused xinit: server error

And I was not able to find any advice that worked.

One more thing is that I tried to do a fsck from a 20.04 live-USB and it crashed partway through to a black screen.

WORKROUND

If I go into the grub menu during booting, and select an older kernel, the problem persists.

However, if I go into any kernel's Recovery Mode and then select the option to Continue with Normal Boot, it will boot normally and run whatever programs etc. The problem I mentioned above of it keeps returning to a flashing cursor also ends and I don't keep having to press Ctrl+Alt+F1.

Next I will try and check the boot disk for bad sectors. It is a SSD and I have a vague awareness that sometimes in a catastrophe they can write-protect themselves to prevent data loss. But when I've had problems like that in the past it has usually been that the entire filesystem became write-protected and that isn't the case here.

Otherwise my first question is what is the difference between a normal boot and a normal boot that is initiated via Recovery Mode? Since that might be where something has been damaged.

And my second question is what is the flashing cursor appearing in, if not a virtual console? I thought in X everything was in a virtual console (since even the login is in one, and in Linux the login is almost fundamental) but is this flashing cursor being displayed by something at a conceptually even lower layer, such as the BIOS? Or Grub?

Thanks for reading and hope someone can help

Answer 1

After 4 months I was able to solve this.

The problem was that the recommended Nvidia driver (470) had been installed. This particular system needed the 390 driver. For reference it is an Acer Aspire M5910 (so around the year 2008) with an Nvidia GeForce GTX 650.

The kernel version is 5.15.0-101-lowlatency

There seemed to be some difficulty installing the drivers relative to this kernel. Sometimes it would work for one boot and then fail again right after.

In the end I purged Nvidia and reinstalled the 390 version, using these commands from How to change proprietary video driver using the command line?

sudo apt-get autoremove --purge nvidia-* sudo service lightdm stop sudo apt-get install xserver-xorg-video-nouveau sudo ubuntu-drivers install nvidia:390

Along the way I tried rebuilding the grub menu and re-imaging the hard disk, which was also a struggle. This has some relevance to which kernel is used at startup so I should mention it. Something I feel would have helped me is if the well-known Linux 'boot repair' live-usb could diagnose display driver issues. Although this was not really a boot issue at all, it looked like one because of the strange way it broke the display environment even in the TTY. To enter any commands it was necessary to keep switching the session back to Ctrl+Alt+F1 so I could continue typing.

UPDATE: I found that for this system the 390 driver was not the best I'd been able to install and apparently it is becoming obsolete. I was able to upgrade to nvidia-driver-470-server (proprietary) through the GUI. The (proprietary, tested) option broke the system every time. The kernel is still stuck at 5.15.0-101-lowlatency.