What is the keyboard combination for SysRq on a Thinkpad T400p?

Support
7

:flushed:

to release both what? a or b variant below?

a) 1st item: (Alt) and 2nd item: (Fn+S)
OR
b) 1st item (Fn) and 2nd item: (S)
?

The same in another words: Does Alt should be uninterruptedly pressed fro the very start of SysRq call and all the time 'till the end of REISUB phrase typing?

8

Remember, Fn+S = SysRq. Treat it as such. :wink:

9

Thanks Yochanan for a great explanation.

Unfortunately Holding Alt then Fn + S, releasing Fn + S (whilst still holding Alt) and entering REISUB does not work for me.

10

Found the manual:

Fn+PrtSc Has the same function as the SysRq key.

2 Likes
11

That was a really cool thing to do, thank you.

Holding Fn+PrtScr whilst entering REISUB does not work for me. Is there a way REISUB could have been disabled?

This is a video of I am doing when I enter REISUB:

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Why do you still hold your SysRq while typing REISUB??? As i undestand you need to call it and to release then.
Are you tried to type REISUB keys with 0.5-1 seconds delay or typed whole 6 chars during a single second?

13

It’s not enabled by default.

Or…

1 Like
14

I managed to get a different distro on another machine to REISUB once by holding the SysRq key whilst typing out REISUB.

That being said:
if I press Fn + PrtSc, release both and type REISUB it does not work;
if I press Fn + PrtSc, release the PrtSc key and type REISUB it does not work.

15

Hold Alt the whole time while you…

16

I have entered the following terminal command:

    ~  echo kernel.sysrq=1 | sudo tee --append /etc/sysctl.d/99-sysctl.conf
Swipe your finger across the fingerprint reader
kernel.sysrq=1

I tried holding alt the whole time, pressing Fn + PrtSc, releasing Fn + PrtSc, then entering REISUB. I could not get this to work

17

That doesn’t take effect immediately, did you reboot after doing that?

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18

I have rebooted but it is still the same as before.

19

Output of

cat /etc/sysctl.d/99-sysctl.conf

please?

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20

Just FYI; you can test it by running journalctl -f and then do Alt+SysRq+h.

If it’s working you’ll get sysrq help output into journal:

kernel: sysrq: HELP : loglevel(0-9) reboot(b) crash(c) terminate-all-tasks(e) memory-full-oom-kill(f) kill-all-tasks(i) thaw-filesystems(j) sak(k) show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-RT-tasks(n) poweroff(o) show-registers(p) show-all-timers(q) unraw(r) sync(s) show-task-states(t) unmount(u) force-fb(v) show-blocked-tasks(w) dump-ftrace-buffer(z)

Edit to expand on this:

If you can’t find SysRq key and still want to test if functionality is enabled, you can instead try:
echo h | sudo tee /proc/sysrq-trigger

3 Likes
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    ~  cat /etc/sysctl.d/99-sysctl.conf                                  
kernel.sysrq=1
1 Like
22

This is the output of holding alt+Fn+PrtSc and typing REISUB looks most similar (pasted excluding a lot of Touchégg daemon errors):

Feb 02 14:52:52 Think kernel: sysrq: HELP : loglevel(0-9) reboot(b) crash(c) terminate-all-tasks(e) memory-full-oom-kill(f) kill-all-tasks(i) thaw-filesystems(j) sak(k) show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-RT-tasks(n) poweroff(o) show-registers(p) show-all-timers(q) unraw(r) sync(s) show-task-states(t) unmount(u) force-fb(v) show-blocked-tasks(w) dump-ftrace-buffer(z) 
Feb 02 14:52:52 Think kernel: sysrq: HELP : loglevel(0-9) reboot(b) crash(c) terminate-all-tasks(e) memory-full-oom-kill(f) kill-all-tasks(i) thaw-filesystems(j) sak(k) show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-RT-tasks(n) poweroff(o) show-registers(p) show-all-timers(q) unraw(r) sync(s) show-task-states(t) unmount(u) force-fb(v) show-blocked-tasks(w) dump-ftrace-buffer(z)

The output whilst pressing and releasing Fn+PrtSc, then entering REISUB whilst still holding alt:

^[r^[e^[i^[s^[u^[b
23

So it is working then. HELP line gets printed only when you press a key that has no function. So you must be pressing something wrong. REISUB only works for QWERTY/AZERTY/etc, so if you are using some other layout, you need to press other keys.

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echo h | sudo tee /proc/sysrq-trigger

This is the output :

    ~   echo h | sudo tee /proc/sysrq-trigger                                ✔ 
Swipe your finger across the fingerprint reader
h

Having re-read my last post I should clarify running Just FYI; you can test it by running journalctl -f and then doing Alt+SysRq+h gives no output.

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It’s in the journal - same HELP line as with pressing actual keys.

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I am using what look like a qwerty keyboard to me :man_shrugging: