topic Re: Urgant: crash dump does not created in Operating System - Linux

Urgant: crash dump does not created

Fadia Almarei — Wed, 29 Dec 2010 11:48:00 GMT

Dear All

i have SLES11 OS running on DL585 G6 server , the server running oracle RAC with another nodes , i have the system crash , i try to create the crash dump file using atl+sys rq+c , but it soes not work and the system still hang what should i do.

BR;
fadia Almarei

Re: Urgant: crash dump does not created

Chhaya_Z — Wed, 29 Dec 2010 15:21:26 GMT

Hi,

Please check the setting for sysrq

Refer the below article "Set up magic SysRq (recommended)"

http://www.novell.com/support/viewContent.do?externalId=3374462

Hope this helps

Re: Urgant: crash dump does not created

Fadia Almarei — Thu, 30 Dec 2010 07:42:23 GMT

i work on this document and every thing is configured OK , i want to know if no crash file created is this mean that there is no crash in the OS and it is just hang ?

Re: Urgant: crash dump does not created

Chhaya_Z — Thu, 30 Dec 2010 09:45:30 GMT

Hi,

"i have the system crash , i try to create the crash dump file using atl+sys rq+c ,"
The above statement says that you had a server crash. Was it a kernel panic, hung, oops or badly hung that it didnot even take keyboard strokes?

A vmcore is generated only under these 5 conditions:
1>die()
2>panic()
3>â Alt-SYSRQ-câ keyboard interrupt is received (sysrq key combination must be enabled)
4>Character â câ is echoed to /proc/sysrq-trigger (sysrq key combination must be enabled)
5>NMI issued via iLO on HP Proliant Servers

3 and 4 Manually calls kdump & generates vmcore (e.g. when the system is hung or frozen, you can manually crash the server using SYSRQ keys to generate a vmcore).

So if the server was hung and all the setting are correct it should have generated the vmcore.

Hope this recommended setting is also set correctly:
Set up magic SysRq (recommended)

For kernel problems other than a kernel oops or panic, a kernel core dump is not triggered automatically. If the system still responds to keyboard input to some degree, a kernel core dump can be triggered manually through a "magic SysRq" keyboard combination (typically: hold down three keys simultaneously: the left Alt key, the Print Screen / SysRq key and a letter key indicating the command - ' s' for sync, ' c' for core dump), if this feature has been enabled.

For general documentation of the "magic SysRq" feature, please refer to the Documentation/sysrq.txt file in the Linux kernel source.

To enable the magic SysRq feature permanently, edit /etc/sysconfig/sysctl, change the ENABLE_SYSRQ line to ENABLE_SYSRQ="yes". This change becomes active after a reboot. To enable the feature for the running kernel, run
echo 1>/proc/sys/kernel/sysrq

In case it was badly hung that it did not accept the keyboard strokes then you can try the NMI option.

Also was the kdump configuration tested in the past? Have u ever had a vmcore generated in the past?

Re: Urgant: crash dump does not created

Fadia Almarei — Thu, 30 Dec 2010 10:46:16 GMT

i have the system hang before and i do these keys and generate the core dump file, but in the previous 3 cases i could not gerenrate it , all the confgurations are right , the main thing that i use system console from ILO , is this make any differance

Re: Urgant: crash dump does not created

Chhaya_Z — Thu, 30 Dec 2010 17:14:26 GMT

Hi,

Try to switch to text terminal and then try Alt+sysrq+c.

Try to change to text terminal use ctrl+alt +f1