From effd035e347d407b6dee74dd08c0d9c4c084862c Mon Sep 17 00:00:00 2001 From: Pratyush Anand Date: Jul 21 2016 05:56:20 +0000 Subject: howto: Notes on watchdog module handling Update howto with notes on dracut and kernel watchdog module handling. Signed-off-by: Pratyush Anand Acked-by: Dave Young --- diff --git a/kexec-kdump-howto.txt b/kexec-kdump-howto.txt index b4cdc22..38f831e 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 is 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 if there exists at +least one active watchdog and user has not added specifically "-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