Instructions for Configuring KDUMP for RHEL 5
Instructions for Configuring KDUMP for RHEL 5
Solution ID: 34
Created: 7/8/2008
DETAILS:
How to configure kdump for use with RHEL 5 and >
1. Verify the kexec-tools package is installed: rpm -q kexec-tools
2. Configure the /etc/kdump.conf file to specify the location where the vmcore
should be dumped. This can be another server via scp, a RAW device, or a local
filesystem.
3. Modify some boot parameters to reserve a chunk of memory for the capture
kernel. For i386 and x86_64 architectures, edit /etc/grub.conf, and append
crashkernel=128M@16M to the end of the kernel line.
This is an example of /etc/grub.conf with the kdump options added: default=0
timeout=5 splashimage=(hd0,0)/boot/grub/splash.xpm.gz hiddenmenu title Red
Hat Enterprise Linux Client (2.6.17-1.2519.4.21.el5) root (hd0,0) kernel
/boot/vmlinuz-2.6.17-1.2519.4.21.el5 ro root=LABEL=/ rhgb quiet
crashkernel=128M@16M initrd /boot/initrd-2.6.17-1.2519.4.21.el5.img
4. After making the above changes, reboot the system. The 128M of memory
(starting 16M into the memory) is left untouched by the normal system, reserved
for the capture kernel. Note that the output of free -m shows 128M less in total
memory than without this parameter, which is expected this memory is reserved
for dump kernel. i.e. before: free -m total used free shared buffers cached Mem:
16055 903 15151 0 141 551 after: free -m total used free shared buffers cached
Mem: 15927 477 15449 0 102 230 Note: It may be possible to use less than
128M, but testing with only 64M was unreliable.
5. Now that the reserved memory region is set up, turn on the kdump init script
and start the service: chkconfig kdump on service kdump start
6. This should load the kernel image image via kexec, leaving the system ready
to capture a vmcore upon crashing. To test this, force-crash the system using
sysrq: echo "c" > /proc/sysrq-trigger
Note: this causes the kernel to panic, followed by the system restarting into the
kdump kernel. When the boot process gets to the point where it starts the kdump
service, the vmcore.x should be copied out to disk to the location you specified in
the /etc/kdump.conf file. New Page - Edit this Page - Attach File –