From 1e7df3e1f355da4fe0eca6422479963f7e772bf8 Mon Sep 17 00:00:00 2001 From: Coiby Xu Date: Tue, 1 Mar 2022 17:30:50 +0800 Subject: [PATCH] update kexec-kdump-howto 1. yum is deprecated so use dnf instead 2. use the "kdumpctl reset-crashkernel" API 3. ask the users to refer to crashkernel-howto.txt for setting custom crashkernel value 4. fix a typo Philipp Rudo Signed-off-by: Coiby Xu --- kexec-kdump-howto.txt | 32 ++++++++++++++++++++------------ 1 file changed, 20 insertions(+), 12 deletions(-) diff --git a/kexec-kdump-howto.txt b/kexec-kdump-howto.txt index 1aeffc7..6741faf 100644 --- a/kexec-kdump-howto.txt +++ b/kexec-kdump-howto.txt @@ -44,7 +44,7 @@ ia64 and ppc64. If you're reading this document, you should already have kexec-tools installed. If not, you install it via the following command: - # yum install kexec-tools + # dnf install kexec-tools Now load a kernel with kexec: @@ -66,23 +66,31 @@ How to configure kdump Again, we assume if you're reading this document, you should already have kexec-tools installed. If not, you install it via the following command: - # yum install kexec-tools + # dnf install kexec-tools To be able to do much of anything interesting in the way of debug analysis, you'll also need to install the kernel-debuginfo package, of the same arch as your running kernel, and the crash utility: - # yum --enablerepo=\*debuginfo install kernel-debuginfo.$(uname -m) crash + # dnf --enablerepo=\*debuginfo install kernel-debuginfo.$(uname -m) crash -Next up, we need to modify some boot parameters to reserve a chunk of memory for -the capture kernel. With the help of grubby, it's very easy to append -"crashkernel=128M" to the end of your kernel boot parameters. Note that the X -values are such that X = the amount of memory to reserve for the capture kernel. -And based on arch and system configuration, one might require more than 128M to -be reserved for kdump. One need to experiment and test kdump, if 128M is not -sufficient, try reserving more memory. +Next up, we need to reserve a chunk of memory for the capture kernel. To use +the default crashkernel value, you can kdumpctl: - # grubby --args="crashkernel=128M" --update-kernel=/boot/vmlinuz-`uname -r` + # kdumpctl reset-crashkernel --kernel=/boot/vmlinuz-`uname -r` + +If the default value does not work for your setup you can use + + # grubby --args="crashkernel=256M" --update-kernel=/boot/vmlinuz-`uname -r` + +to specify a larger value, in this case 256M. You need to experiment to +find the best value that works for your setup. To begin with + + # kdumpctl estimate + +gives you an estimation for the crashkernel value based on the currently +running kernel. For more details, please refer to the "Estimate crashkernel" +section in /usr/share/doc/kexec-tools/crashkernel-howto.txt. Note that there is an alternative form in which to specify a crashkernel memory reservation, in the event that more control is needed over the size and @@ -135,7 +143,7 @@ in /var/crash//vmcore), then the system rebooted back into your normal kernel. Once back to your normal kernel, you can use the previously installed crash -kernel in conjunction with the previously installed kernel-debuginfo to +utility in conjunction with the previously installed kernel-debuginfo to perform postmortem analysis: # crash /usr/lib/debug/lib/modules/2.6.17-1.2621.el5/vmlinux