Installation guide

158 Appendix A:Supplementary Hardware Information
In order to determine if the server supports the NMI watchdog timer, first try adding "nmi_watch-
dog=1" to the kernel command line as described above. After the system has booted, log in as root
and type:
cat /proc/interrupts
The output should appear similar to the following:
CPU0
0: 5623100 XT-PIC timer
1: 13 XT-PIC keyboard
2: 0 XT-PIC cascade
7: 0 XT-PIC usb-ohci
8: 1 XT-PIC rtc
9: 794332 XT-PIC aic7xxx, aic7xxx
10: 569498 XT-PIC eth0
12: 24 XT-PIC PS/2 Mouse
14: 0 XT-PIC ide0
NMI: 5620998
LOC: 5623358
ERR: 0
MIS: 0
The relevant portion of the above output is to verify that the NMI id appears on the left side. If NMI
value (in the middle column) is non-zero, the server supports the NMI watchdog.
If this approach fails, that is, NMI is zero, try passing nmi_watchdog=2 to the kernel instead of
nmi_watchdog=1 in the manner described previously. Again, check /proc/interrupts after the system
boots. If NMI is non-zero, the NMI watchdog has been configured properly. If NMI is zero, your
system does not support the NMI watchdog timer.
Configuring a Hardware Watchdog Timer
The kernel provides driver support for various types of hardware watchdog timers. Some of these
timers are implemented directly on the system board, whereas others are separate hardware compo-
nents such as PCI cards. Hardware based watchdog timers provide excellent data integrity provisions
in the cluster because they operate independently of the system processor and are therefore fully op-
erational in rebooting a system in the event of a system hang.
Due to a lack of uniformity among low-level hardware watchdog components, it is difficult to make
generalizations describing how to know if a particular system contains such components. Many low-
level hardware watchdog components are not self-identifying.
The kernel provides support for the following hardware watchdog variants listed in Table A–2, Hard-
ware Watchdog Timers :