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YesSymptoms
Sometimes it is useful to configure kernel crash dumps in order to troubleshoot panics on the Parallels Server Bare Metal or Parallels Virtuozzo Containers for Linux.
NOTE: IN RHEL 6.x-BASED DISTRIBUTIONS, KEXEC IS BUILT-IN AND THE BELOW STEPS ARE NOT REQUIRED.
NOTE: For kernels 2.6.32-042stabXXX and newer makes, be sure to use the "crashkernel=129M@0M" option in p.2.
Resolution
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Install kexec-tools on the Hardware Node:
[root@pvcfl46x64 ~]# yum install kexec-tools -
Append GRUB configuration with kernel option "crashkernel=128M@16M" for i386 or x86_64 and with "crashkernel=256M@256M" for Itanium for PVC versions prior to 4.7. For versions more recent than 4.7, consider using "crashkernel=129M@0M" for i386 and x86_64 architectures.
[root@pvcfl46x64 ~]# grep crash /etc/grub.conf
kernel /boot/vmlinuz-2.6.18-028stab070.14 ro root=LABEL=/1 debug console=ttyS0,115200 console=tty crashkernel=128M@16M - Reboot HW.
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Enable Kdump on HW:
[root@pvcfl46x64 ~]# chkconfig kdump on
[root@pvcfl46x64 ~]# chkconfig --list kdump
kdump 0:off 1:off 2:on 3:on 4:on 5:on 6:off -
Start Kdump on HW:
[root@pvcfl46x64 ~]# service kdump start
No kdump initial ramdisk found. [WARNING]
Rebuilding /boot/initrd-2.6.18-028stab070.14kdump.img
Starting kdump: [ OK ]
NOTE: If you are configuring crash dumps on Parallels Server Bare Metal machine it is necessary to disable Parallels Hypervisor before creating initrd image:
service parallels-server stop
touch /etc/kdump.conf
service kdump restart -
If you want to store dumps on the external server, then additional steps are required. Edit "/etc/kdump.conf" to use the appropriate server:
[root@pvcfl46x64 ~]# cat /etc/kdump.conf
net root@10.55.63.11
path /var/crash/pvcfl46x64/Note: Make sure that the partition is specified and that the "path" is big enough to store kernel dumps. The amount of available free space should be enough to store several dumps of a size equal to the RAM.
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Propagate settings:
[root@pvcfl46x64 ~]# service kdump propagate
Generating new ssh keys... done.
root@10.55.63.11's password:
/root/.ssh/kdump_id_rsa.pub has been added to ~root/.ssh/authorized_keys2 on 10.55.63.11
[root@pvcfl46x64 ~]# -
Restart Kdump:
[root@pvcfl46x64 ~]# service kdump restart
Stopping kdump: [ OK ]
Detected change(s) the following file(s):
/etc/kdump.conf
Rebuilding /boot/initrd-2.6.18-028stab070.14kdump.img
Starting kdump: [ OK ]
[root@pvcfl46x64 ~]#
Now, when the kernel crashes, the dump can be found under "/var/crash/pvcfl46x64/."
On a non-production server, you can test the configuration as follows:
echo 1 > /proc/sys/kernel/sysrq
echo c > /proc/sysrq-trigger
If everything is OK, you should see an output on the server console that looks similar to that displayed below:
The crash dump should appear as follows:
[root@pvcfl46x64 ~]# ls -la /var/crash/2011-03-03-05\:55/
total 649940
drwxr-xr-x 2 root root 4096 Mar 3 05:56 .
drwxr-xr-x 3 root root 4096 Mar 3 05:55 ..
-r-------- 1 root root 2018588492 Mar 3 05:56 vmcoreAdditional information
Parallels Containers user guide:Using Kexec and Kdump For System Troubleshooting
Dedoimedo.com also has a lot of useful information about kernel crashes troubleshooting:
Analyzing Linux kernel crash dumps with crash - The one tutorial that has it all
Collecting and analyzing Linux kernel crashes - Kdump