How to obtain kdump if server hung

Assuming you already have KDUMP configured and functioning .

If you need to generate a coredump from server without physical access to it you may want to enable kernel to call the panic routine when it receives an unknown NMI, to do it you have to edit /etc/sysctl.conf and add following line:

kernel.unknown_nmi_panic = 1

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To generate a core you may use some web based ‘KVM’ services, most of them has ability to send NMI to host. Another possible way in case of IPMI has been configured is to send unknown NMI with impitool command:

 


 

In case of “BUG: soft lockup – CPU#7 stuck for 67s” messages in /var/log/message to have core file created automatically you need to switch kernel.softlockup_panic to 1:

Edit /etc/sysctl.conf and insert following line:

kernel.softlockup_panic = 1

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