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I managed to get myself into quite the corner.

I messed up permissions to /usr/bin/ and all subdirectories, e.g. root is no longer owner of /usr/bin/sudo. As a result, I get the infamous /usr/bin/sudo must be owned by uid 0 and have the setuid bit set error, which I found the above link to solve.

However, when I try to boot to either Recovery or an installation USB to re-install Ubuntu, I only get a black screen when trying to enter grub. From posts like this and this, I've gathered that grub is hidden in recent releases of Ubuntu. The issue now is that I cannot edit /etc/default/grub since I don't have sudo access...and we've come full circle.

EDIT:

I now believe that my blank screen when I press ESC at boot is because of nouveau kernel drivers, per this link. But I cannot disable those at grub during boot without sudo access.

ndeboldt
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  • can you boot from a Live USB? – pLumo Nov 02 '23 at 17:21
  • My understanding is that you have to enter grub to do that. Is there another way? – ndeboldt Nov 02 '23 at 17:22
  • @ndeboldt USB boot is handled by your system firmware, not GRUB. You should be able to boot to a liveusb (installer USB) to modify the installes system from the functional Live environment – Thomas Ward Nov 02 '23 at 18:34
  • there should be a keyboard key to show grub during boot. IIRC correctly you need to hold SHIFT during boot. – Rinzwind Nov 02 '23 at 19:29
  • A single hit on ESC, as the BIOS/UEFI texts appear, should make the grub menu show up. In the menu select recovery mode, use fsck and network options, then "drop to root prompt". – Hannu Nov 02 '23 at 19:49
  • I've tried that - It's a repurposed Mac Pro, so UEFI not BIOS, but ESC should get me there. But I just get a blank screen, no grub. Maybe it's a separate issue?

    I've read through a similar sounding issue here:

    https://askubuntu.com/questions/1246482/i-got-a-black-screen-every-time-ubuntu-boots-and-i-cant-get-to-the-grub-menu

    But all of the solutions require sudo access... which brings me back to square 0

     – ndeboldt Nov 02 '23 at 20:18

1 Answers1

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I ended up fixing it, although I don't feel particularly elegant with my solution.

In the end, I disconnected my boot SSD and turned on the computer with the live USB I created connected. Grub came up and I was able to boot from the live USB. I elected to re-install Ubuntu from the USB, and reconnected my SSD. It was recognized and I was able to install to it. Problem solved!

ndeboldt
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