In the past I've found that the console may have blanked (due to time) and
when the system locked up/hung it won't unblank. Booting with
"consoleblank=0" on the kernel command line will ensure that whatever is
printed to the console (oops, panic, etc) will be there for you to see when
you connect.
I've had intermittent success in that type of situation with the SysRq
key(s), see https://en.wikipedia.org/wiki/Magic_SysRq_key . They do
require that you have it configured/enabled ahead of time. If you access
the console over a BMC/IPMI KVM session it can be very difficult, if not
impossible, to enter the keystroke as well.
Good luck,
Scott
On Wed, May 22, 2019 at 8:46 AM Stephen John Smoogen <smooge@xxxxxxxxx>
wrote:
> On Wed, 22 May 2019 at 09:30, mark <m.roth@xxxxxxxxx> wrote:
>
> > Ok, we used to get this occasionally on cluster nodes, and we just got it
> > on a fileserver (very bad). The system is discovered to be unresponsive:
> > it doesn't ping, and plugging a console in, you can see that it's not
> > dead, but there nothing at all on the screen, nor does it respond to even
> > <ctrl-alt-del>. The only answer is to power cycle it; it comes up fine.
> >
> > Nothing in /var/log/dmesg or /var/log/messages. No abrts I can find. sar
> > tells me it went unredponsive between 18:10 and 10:20 yesterday. Note
> that
> > there are no further entries in sar, either, for yesterday, after the
> > event, and nothing till I power cycled it.
> >
> >
> From the above description, I would normally say it sounds like hardware.
> However, why do you say the system is not dead when you plug in a console..
> but there is nothing on the screen and it doesn't respond to
> control-alt-delete. To me that sounds like 'dead'. Usually the cpu is
> hardlocked or the hardware went into 'over-heat' and put everything in a
> deep sleep hoping it would cool down but never wake up.
>
>
>
> > Has anyone else seen this - I can't imagine it's only us - or have any
> > thoughts?
> >
> > C 7, 7.6.1810
> >
> > mark
> >
> >
> > _______________________________________________
> > CentOS mailing list
> > CentOS@xxxxxxxxxx
> > https://lists.centos.org/mailman/listinfo/centos
> >
>
>
> --
> Stephen J Smoogen.
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> https://lists.centos.org/mailman/listinfo/centos
>
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