[PATCH V4 3/5] howto: Notes on watchdog module handling

Update howto with notes on dracut and kernel watchdog module handling. Signed-off-by: Pratyush Anand <panand(a)redhat.com&gt; --- kexec-kdump-howto.txt | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/kexec-kdump-howto.txt b/kexec-kdump-howto.txt index b4cdc2227f1d..83b3e0a0645f 100644 --- a/kexec-kdump-howto.txt +++ b/kexec-kdump-howto.txt @@ -616,6 +616,20 @@ options are copied from /proc/cmdline. In general it is best to append command line options using "KDUMP_COMMANDLINE_APPEND=" instead of replacing the original command line completely. +Notes on watchdog module handling: + +If a watchdog is active in first kernel then, we must have it's module +loaded in crash kernel, so that either watchdog is deactivated or started +being kicked in second kernel. Otherwise, we might face watchdog reboot +when vmcore was being saved. When dracut watchdog module is enabled, it +installs kernel watchdog module of active watchdog device in initrd. +kexec-tools always add "-a watchdog" to the dracut_args until user +specifically adds "-o watchdog" in dracut_args of kdump.conf. If a +watchdog module (such as hp_wdt) has not been written in watchdog-core +framework then this option will not have any effect and module will not be +added. Please note that only systemd watchdog daemon is supported as +watchdog kick application. + Parallel Dumping Operation ========================== Kexec allows kdump using multiple cpus. So parallel feature can accelerate -- 2.5.5