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[Solved]PC froze, now what? (discuss.tchncs.de)

submitted 5 days ago* (last edited 4 days ago) by [email protected] to c/linux4noobs

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What do I do, when my PC freezes?

Windows has ctrl+alt+del, does Linux Mint has something comparable? The only thing I know about is REISUB, but that borked my PC, so I am hesitant to use that again.

Are there any remaining alternatives to waiting and/or using the power button?

Edit: Thank you all for your insights and possible fixes. Crashes usually happened when I was running (cpu/ram?) heavy workload. Increasing swap space was not even on my radar, so I did that now. :) Hopefully Mint will run more stable now.

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[–] [email protected] 1 points 4 days ago

Tried F1-6, no love. Only thing that does respond is the mouse movement... keyboard only responds to input reisub. I think if I am at keyboard and the screen does not lock, any windows open will respond to mouse hover but not clicks... I need a linux doctor lol. Maybe a second display for outputting kernel logs, that would be fun for dev work. Though I feel like ssh is the defacto way to accomplish that... Anything we can accomplish with one host and two displays, no network?

Prompted GPT

It sounds like you're encountering a kernel-level or X/Wayland-level freeze while developing. The fact that the keyboard is unresponsive except for REISUB suggests a deep hang in the graphical session or related system processes.

Here’s a practical way to debug and diagnose this issue with two displays and one host, without needing a network:

Setup for Debugging on Two Displays

Enable Persistent Kernel Logs on Second Display:
- Use a TTY session on your second display to monitor kernel logs.
- Connect your second display and switch to it using Ctrl+Alt+F2 (or F3-F6, depending on availability).
- Login and run:
```
sudo tail -f /var/log/kern.log
```
  or
```
sudo dmesg -w
```
- This will show you kernel logs in real time, which is often critical for diagnosing freezes.
Mirror Logs or Virtual Console Across Displays:
- If your second display doesn't switch TTYs independently, use a terminal multiplexer (like tmux or screen) to duplicate the kernel log view.
  - Start tmux in TTY1 and attach to it from TTY2:
```
tmux
tail -f /var/log/kern.log
```
    Then on the second TTY:
```
tmux attach
```

Improve Debugging Workflow

Set Up Magic SysRq for More Control:
- If your system allows REISUB, the Magic SysRq key is already enabled. You can use other commands to debug live:
  - Sync and Kill Tasks: Alt + SysRq + F can attempt to kill resource-hogging processes.
  - Toggle TTY: Alt + SysRq + R can re-enable raw keyboard input if the GUI is frozen.
Enable Kernel Debugging Outputs:
- Append debug to your kernel boot parameters in GRUB:
  - Edit /etc/default/grub:
```
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash debug"
```
  - Update GRUB and reboot:
```
sudo update-grub
```
- This provides richer debugging output in logs.
Use a Non-GUI Target:
- For safer development, switch to a lower system target to prevent full GUI freezes:
```
sudo systemctl set-default multi-user.target
```
  - Reboot into a non-GUI mode where you can manually start your app, making it easier to debug without freezing the entire desktop.
Forcefully Isolate the Process:
- Run your wallpaper application in a separate X server to isolate it:
```
xinit /path/to/your/app -- :1
```
  - This starts a new X session on display :1 while keeping your primary desktop untouched.

Tips to Prevent GUI Freezes During Development

Limit CPU or Memory Usage:
- Use ulimit to restrict resource usage of your program:
```
ulimit -v 1048576  # Limit to 1GB virtual memory
```
Log Debugging Information:
- Add debug prints in your app and log them to a file instead of stdout.