[Linux-cluster] problem with deadlocked processes (D)

[Bryn M. Reeves]

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rhurst at bidmc.harvard.edu wrote:
> Are these two kernel sysctl parameters recommended to be enabled all the
> time, particularly with production GFS/clustered systems, or only for
> dev/test systems for debugging purposes?  Thanks.
> 

Only the first of these is a kernel parameter (kernel.sysrq). It enables
keyboard sysrqs (holding down alt-sysrq-$KEY to trigger a sysrq command).

This is off by default as it means anyone with console access can do
"bad stuff" (reboot, DoS with thread dumps, SAKs etc). If physical
access is sufficiently secure you can leave them on all the time - I do
this on all my lab/test boxes. For production it all depends on your
situation.

The second is just a trigger (/proc/sysrq-trigger). Echoing a char into
there just triggers the corresponding sysrq action once. This does not
need /proc/sys/kernel/sysrq enabled since only root has write access to
the file.

Regards,
Bryn.

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