You need to change the kernel parameter (Note that this is not a kernel cmdline parameter. Adding to grub etc doesn't work):
kernel.sysrq = 1
with sysctl or,
# echo 1 > /proc/sys/kernel/sysrq
To enable all SysRq commands temporarily. The linuxconfig.org article shows permanent change as well.
For those who are looking for the SysRq magic on Dell laptops, I think this alt+fn+r combination works in general (mine Precision 7550, works).
One thing to clarify for others: you spelled capital R, I thought this was a shift+r. Which wasn't. To execute 1 or many (chaining) SysRq commands (the method worked on my device flawlessly):
1. Sequentially press & hold Alt+Fn+R (first press Alt; while holding Alt, press Fn; while holding Alt+Fn, press R) (lowercase R, not shift+R, just the R key)
2. Now you can release Fn and R keys. Release order doesn't matter, so long as you are holding Alt since the 1st step.
3. While holding Alt, press & release the desired SysRq command key: e.g. "m" for the mem info dump.
(4. Now, still, without releasing Alt, you can issue new SysRq commands one after another.)
Caveat: consecutive SysRq commands sometimes don't work, and the kernel simply ignores your requests. Possible solns to this problem are presented in the kernel.org article.
I am using LightDM, which uses tty7. So I can view kernel messages on tty1. e.g to see the mem info dump, go to tty1 and issue SysRq commands and immediately view results. Interestingly enough SysRq+h does not work on me, even with kernel.sysrq=1. Additionally, I have the
Option "DontVTSwitch" "True"
As a ServerFlag on my Xorg config, which disables switching to other ttys. After issuing a SysRq+r, Ctrl+Alt+F# can switch ttys now.
bbulguroglu21
1 Rookie
•
1 Message
1
June 4th, 2022 19:00
Hello,
Please check out the following links. They have the solutions to your problem.
https://linuxconfig.org/how-to-enable-all-sysrq-functions-on-linux
https://www.kernel.org/doc/html/latest/admin-guide/sysrq.html
https://en.m.wikipedia.org/wiki/Magic_SysRq_key
You need to change the kernel parameter (Note that this is not a kernel cmdline parameter. Adding to grub etc doesn't work):
with sysctl or,
To enable all SysRq commands temporarily. The linuxconfig.org article shows permanent change as well.
For those who are looking for the SysRq magic on Dell laptops, I think this alt+fn+r combination works in general (mine Precision 7550, works).
One thing to clarify for others: you spelled capital R, I thought this was a shift+r. Which wasn't. To execute 1 or many (chaining) SysRq commands (the method worked on my device flawlessly):
1. Sequentially press & hold Alt+Fn+R (first press Alt; while holding Alt, press Fn; while holding Alt+Fn, press R) (lowercase R, not shift+R, just the R key)
2. Now you can release Fn and R keys. Release order doesn't matter, so long as you are holding Alt since the 1st step.
3. While holding Alt, press & release the desired SysRq command key: e.g. "m" for the mem info dump.
(4. Now, still, without releasing Alt, you can issue new SysRq commands one after another.)
Caveat: consecutive SysRq commands sometimes don't work, and the kernel simply ignores your requests. Possible solns to this problem are presented in the kernel.org article.
I am using LightDM, which uses tty7. So I can view kernel messages on tty1. e.g to see the mem info dump, go to tty1 and issue SysRq commands and immediately view results. Interestingly enough SysRq+h does not work on me, even with kernel.sysrq=1. Additionally, I have the
As a ServerFlag on my Xorg config, which disables switching to other ttys. After issuing a SysRq+r, Ctrl+Alt+F# can switch ttys now.
A5.
2 Posts
0
June 20th, 2023 06:00
"alt+fn+r" makes pressing "alternative + function + R" and that produces "Shift_Left+Print" and that produces a full screen shot, nothing more