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 NVIDIA Driver Upgrade - Root Workflow (sudo -i)
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CURRENT STATE
  - Debian 550 packages: installed but DKMS not built
  - Active driver: nouveau (fallback)
  - GUI works via nouveau + Intel iGPU

PATHS (use absolute paths because $HOME = /root under sudo -i)
  Driver file : /home/dk/nvidia-upgrade/NVIDIA-Linux-x86_64-580.105.08.run
  Install     : /home/dk/nvidia-upgrade/02-install.sh
  Rollback    : /home/dk/nvidia-upgrade/03-rollback.sh
  Logs        : /home/dk/nvidia-upgrade/logs/

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 OPTION A: Upgrade to 580 (recommended)
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Step 1: Switch to TTY -> Ctrl + Alt + F3
        Login as 'dk' + password

Step 2: Become root
        sudo -i

Step 3: Run installer
        bash /home/dk/nvidia-upgrade/02-install.sh

  The script is fully non-interactive.
  All output is in English and saved to:
      /home/dk/nvidia-upgrade/logs/install-*.log

Step 4: Reboot
        reboot

Step 5 (back in GUI):
        nvidia-smi          -> should show 580.105.08
        cat /sys/module/nvidia_drm/parameters/modeset   -> Y

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 OPTION B: Just restore working 550 driver
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Step 1: Ctrl + Alt + F3 -> login as dk
Step 2: sudo -i
Step 3: bash /home/dk/nvidia-upgrade/03-rollback.sh
Step 4: reboot

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 IF SOMETHING GOES WRONG
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GUI does NOT come back after reboot:
  - At login screen, press Ctrl + Alt + F3
  - Login as dk
  - sudo -i
  - bash /home/dk/nvidia-upgrade/03-rollback.sh
  - reboot

Read log files (back in GUI):
    less /home/dk/nvidia-upgrade/logs/install-XXXXXX.log
    (press q to quit)

List logs:
    ls -la /home/dk/nvidia-upgrade/logs/

Switch TTY -> GUI:
    Ctrl + Alt + F2   (or F1 / F7)

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 TTY NOTES (no Chinese display)
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The Linux console cannot render Chinese characters.
That is why scripts now output English only.

If you want Chinese in TTY in the future:
    apt install kmscon
Then use Ctrl+Alt+F4 (kmscon) instead of F3 (agetty).

Alternative: SSH from phone (Termux on Android)
    ip a                 # find IP
    ssh dk@<IP>          # from phone, full Chinese support