What do you mean? Wouldn't the kernel version always be the actual running version of the kernel that was booted?

Ben

On 3/26/19 6:16 PM, wuzhouhui wrote:

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-----Original Messages----- From: "Benjamin Hauger" hauger@noao.edu Sent Time: 2019-03-27 00:15:21 (Wednesday) To: centos@centos.org Cc: Subject: Re: [CentOS] How to specify kernel version when restart kdump

kdump operates by booting a fresh kernel to capture the context of a crashed kernel, and so the only way for kdump to dump a kernel is to crash it and cause kdump to invoke its post-crash kernel.

You can manually force a running kernel to panic (and invoke a correctly-configured kdump) with the following command sequence:

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 echo 1 > /proc/sys/kernel/sysrq
 echo c > /proc/sysrq-trigger

Cheers, Ben

Hi, Ben

I think your response doesn't answered my question. I'm not asking how to trigger kernel crash and see whether the kdump is works, but asking how to specifying kernel version when start kdump service.

Thanks.

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On 3/25/19 7:19 PM, wuzhouhui wrote: CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos

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CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos

On Thu, Mar 28, 2019 at 6:55 AM wuzhouhui wuzhouhui14@mails.ucas.ac.cn wrote:

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-----Original Messages----- From: "Benjamin Hauger" hauger@noao.edu Sent Time: 2019-03-28 01:31:40 (Thursday) To: wuzhouhui wuzhouhui14@mails.ucas.ac.cn, centos@centos.org Cc: Subject: Re: [CentOS] How to specify kernel version when restart kdump

What do you mean? Wouldn't the kernel version always be the actual running version of the kernel that was booted?

Suppose the running kernel is 2.6.32, and then I installed kernel 3.10.0. The files under /boot includes (exclude some unimportant files): initramfs-2.6.32.img initramfs-3.10.0.img vmlinuz-2.6.32 vmlinuz-3.10.0 initrd-2.6.32kdump.img We can see that there is no initrd-3.10.0kdump.img for newly installed kernel 3.10.0, and kdump will generate initrd-3.10.0kdump.img only when booted as kernel 3.10.0. However, I want kdump to generate initrd-3.10.0kdump.img now (the current running kernel is 2.6.32).

Your particolar versions seem quite strange because 2.6.32 lets me think about CentOS 6 and 3.10.0 lets me think about CentOS 7. Any way see below for some discussion, not tried by me, so in case please use on test system before.

1) In CentOS 6 we have the classical SysV service file: /etc/rc.d/init.d/kdump

Supposing you have just installed 2.6.32-642.13.1.el6.x86_64 kernel

Analyzing what it runs we have

DUMP_KERNELVER="" MKDUMPRD_ARGS=""

. /etc/sysconfig/kdump In my case: KDUMP_BOOTDIR="/boot"

local running_kernel=`uname -r` kdump_kver=`echo $running_kernel | sed 's/smp//g'` MKDUMPRD="/sbin/mkdumprd -d -f $MKDUMPRD_ARGS"

kdump_initrd="${KDUMP_BOOTDIR}/initrd-${kdump_kver}kdump.img"

and at the end it runs this command if it doesn't find one: $MKDUMPRD $kdump_initrd $kdump_kver

that tipically will translate in:

/sbin/mkdumprd -d -f "/boot/initrd-2.6.32-642.13.1.el6.x86_64kdump.img"

2) In CentOS 7 we have systemd unit files and for kdump: /usr/lib/systemd/system/kdump.service

Supposing you have just installed 3.10.0-693.21.1.el7.x86_64

The script called actually it is /usr/bin/kdumpctl

See also fadump (firmware assisted dump) concepts in RHEL 7 / CentOS 7: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/htm...

But I think you are x86_64 so kdump sttill applies In kdumpctl we have something like this:

MKDUMPRD="/sbin/mkdumprd -f" TARGET_INITRD=""

. /lib/kdump/kdump-lib.sh

. /etc/sysconfig/kdump

eval $(cat /proc/cmdline| grep "BOOT_IMAGE" | cut -d' ' -f1) KDUMP_BOOTDIR="/boot"$(dirname $BOOT_IMAGE)

kdump_kver=`uname -r` TARGET_INITRD="${KDUMP_BOOTDIR}/initramfs-${kdump_kver}kdump.img"

rebuild_kdump_initrd() { $MKDUMPRD $TARGET_INITRD $kdump_kver if [ $? != 0 ]; then echo "mkdumprd: failed to make kdump initrd" >&2 return 1 fi

return 0 }

So at the end the command will be:

$MKDUMPRD $TARGET_INITRD $kdump_kver

that in general should be something like this if you want to compile for kernel 3.10.0-693.21.1.el7.x86_64 :

/sbin/mkdumprd -f /boot/initramfs-3.10.0-693.21.1.el7.x86_64kdump.img 3.10.0-693.21.1.el7.x86_64

HIH trying, Gianluca

-----Original Messages----- From: "Gianluca Cecchi" gianluca.cecchi@gmail.com Sent Time: 2019-03-28 16:59:19 (Thursday) [...] The command line fo CentOS 6 clearly misses the kernel version to build initrd file for, so the correct command should be:

/sbin/mkdumprd -d -f "/boot/initrd-2.6.32-642.13.1.el6.x86_64kdump.img" 2.6.32-642.13.1.el6.x86_64

I test it and it works for me, although prints some harmless warnings.

Thanks