which magic sysreq keys to gather info on a total system freeze [Solved]

[Danathar]

I've been searching around, and I can't seem to get a clean answer so maybe somebody with more knowledge could give some advice?

I've experienced 2 total system freezes, hard enough that the caps lock becomes unresponsive. I've tried the 6.5 kernel in the respos just in case it was something with the current kernel I was running. I'm on MX 23.1 with KDE and Kernel 6.1.

After doing some searching it seems like I should maybe try some magic sysreq keys to gather more data? Ive checked the logs after reboot, kern.log, syslog, etc and there is simply nothing there. It's a clean break EXCEPT for a bunch of ^@ characters at the part of the syslog where the froze occured. Is this null or something?

There is a WHOLE BUNCH of magic sysreq keys to use here https://www.kernel.org/doc/html/latest/ ... sysrq.html I have no idea which ones would be the best to do.

thoughts?

Greatly appreciate any help. I'd hate to have to toss this laptop.

[Charlie Brown]

R E I S U B

[Danathar]

R E I S U B

That might keep me from doing a hard button reset, but will that help me tell why it occurred? thank you BTW. That is helpful!

[CharlesV]

Shutting down as gracefully as possible will help the logs to be written.

Look in the /var/log folder at the various logs.

Video problems are usually logged in /var/log/Xorg.0.log.

Problems detected by the kernel are logged in /var/log/kern.log or /var/log/messages

Logs with .0. are previous logs.

also the QSI logs are a good place to start.

And usually, lock ups are because of video / audio or ram. (not always ) Turning off Hardware acceleration in your web browser is a great starting point too.

If you will post your QSI that also might give some indicators.. and what applications are running when you encounter the lock up?

[CharlesV]

Some additional information about commands that can help "gracefully" reboot and write out the log files.

https://linuxhandbook.com/frozen-linux-system/

Sysrec.jpg

Code: Select all

Keys 	Description
Alt + SysRq + r 	Takes the keyboard out of raw mode, taking control away from X
Alt + SysRq + e 	Send SigTerm to all process, giving them a chance to quit gracefully
Alt + SysRq + i 	Send SigKill to all process
Alt + SysRq + k 	Kill all process in current virtual console
Alt + SysRq + s 	Sync all mounted filesystem, flushing all data to disk
Alt + SysRq + u 	Remount all filesystem read-only
Alt + SysRq + b 	Reboot system instantly, does not sync or unmount
Alt + SysRq + o 	Shutdown system

[Danathar]

Shutting down as gracefully as possible will help the logs to be written.

Look in the /var/log folder at the various logs.

Video problems are usually logged in /var/log/Xorg.0.log.

Problems detected by the kernel are logged in /var/log/kern.log or /var/log/messages

Logs with .0. are previous logs.

also the QSI logs are a good place to start.

And usually, lock ups are because of video / audio or ram. (not always ) Turning off Hardware acceleration in your web browser is a great starting point too.

If you will post your QSI that also might give some indicators.. and what applications are running when you encounter the lock up?

Thanks. Next time that crash comes around I will post it. The only app was firefox. I had forgotten that in the past I'd encountered (not on MX, but on Ubuntu) a re-producible freeze on firefox playing a youtube channel. Turning off hardware acceleration in the browser fixed it. I'll turn it off and see if I continue to get that.

It makes sense that shutting down gracefully can write stuff you wouldn't see doing a hard reset.

thank you!

[CharlesV]

Your very welcome and hope that resolves it :-)

[Danathar]

Some additional information about commands that can help "gracefully" reboot and write out the log files.

https://linuxhandbook.com/frozen-linux-system/


Sysrec.jpg

Code: Select all

Keys 	Description
Alt + SysRq + r 	Takes the keyboard out of raw mode, taking control away from X
Alt + SysRq + e 	Send SigTerm to all process, giving them a chance to quit gracefully
Alt + SysRq + i 	Send SigKill to all process
Alt + SysRq + k 	Kill all process in current virtual console
Alt + SysRq + s 	Sync all mounted filesystem, flushing all data to disk
Alt + SysRq + u 	Remount all filesystem read-only
Alt + SysRq + b 	Reboot system instantly, does not sync or unmount
Alt + SysRq + o 	Shutdown system

thanks! One interesting thing I found out, at least on the Dell I'm troubleshooting. Its only the left alt that works with printscr to do sysreq. Right alt does not work.

[CharlesV]

I saw this on a laptop I was working on some time back, but I thought it was due to a special map key or something. Interesting!

[MXRobo]

Mostly redundant, but links. https://wiki.archlinux.org/title/keyboa ... el_(SysRq)