12:54 a.m.
Hi, kairui
Thank you for helping review this.
在 2020年12月29日 13:51, Kairui Song 写道:
On Mon, Dec 28, 2020 at 4:48 PM Lianbo Jiang
<lijiang(a)redhat.com> wrote:
>
> Currently, the kdump sysconfig document is missed, let's add it to
> the kexec-kdump-howto.txt as a document in order to help users better
> understand these options in the /etc/sysconfig/kdump.
>
> Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com>
> ---
> kexec-kdump-howto.txt | 85 ++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 80 insertions(+), 5 deletions(-)
>
> diff --git a/kexec-kdump-howto.txt b/kexec-kdump-howto.txt
> index 447bc5447886..206bc1800486 100644
> --- a/kexec-kdump-howto.txt
> +++ b/kexec-kdump-howto.txt
> @@ -524,17 +524,92 @@ to send over the necessary ssh key file. Restart the kdump
service via
> Advanced Setups
> ===============
>
> -Kdump boot directory
> ---------------------
> +About the /etc/sysconfig/kdump
> +------------------------------
> +
> +Currently, there are a few options in the /etc/sysconfig/kdump, which are
> +usually used to control the behavior of kdump kernel. Basically, all of
> +these options have default values, most time we do not need to change them,
> +but sometimes, we may modify them in order to better control the behavior
> +of kdump kernel such as debug, etc.
> +
> +-KDUMP_BOOTDIR
>
> Usually kdump kernel is the same as 1st kernel. So kdump will try to find
> kdump kernel under /boot according to /proc/cmdline. E.g we execute below
> command and get an output:
> cat /proc/cmdline
> BOOT_IMAGE=/xxx/vmlinuz-3.yyy.zzz root=xxxx .....
> -Then kdump kernel will be /boot/xxx/vmlinuz-3.yyy.zzz.
> -However a variable KDUMP_BOOTDIR in /etc/sysconfig/kdump is provided to
> -user if kdump kernel is put in a different directory.
> +
> +Then kdump kernel will be /boot/xxx/vmlinuz-3.yyy.zzz. However, this option
> +is provided to user if kdump kernel is put in a different directory.
Hi Lianbo, this line seems to be redundant?
The above line should be necessary, it will tell user how to set the value of
variable when kdump kernel is put in a different directory instead of default
directory.
> +
> +-KDUMP_IMG
> +
> +This represents the image type used for kdump. The default value is
"vmlinuz"
> +like KDUMP_IMG="vmlinuz". In general, do not change it.
I think this 'like KDUMP_IMG="vmlinuz"' sentence can be dropped. And
just ask user don't change it if they are not sure what this means.
Sounds good. I will improve them based on your comments below.
Thanks.
Lianbo
> +
> +-KDUMP_IMG_EXT
> +
> +This represents the images extension. Relocatable kernels don't have one.
> +Currently, it should be a null string, do not modify it.
Also, here, I think some sentence like "don't change it if you don't
know what it means" is better.
> +
> +-KEXEC_ARGS
> +
> +Any additional kexec arguments required. For example:
> +KEXEC_ARGS="--elf32-core-headers".
> +
> +In most situations, this should be left empty. But, sometimes we hope to get
> +additional kexec loading debugging information, we can add the '-d' option
> +for the debugging.
> +
> +-KDUMP_KERNELVER
> +
> +This is a kernel version string for the kdump kernel. If the version is not
> +specified, the init script will try to find a kdump kernel with the same
> +version number as the running kernel. Usually, no need to modify it.
I think the "no need to modify it" is not necessary, the doc describes
how this params works well.
> +
> +-KDUMP_COMMANDLINE
> +
> +The value of 'KDUMP_COMMANDLINE' will be passed to kdump kernel as command
> +line parameters, this will likely match the contents of the grub kernel line.
> +
> +In general, if a command line is not specified, which means that it is a null
> +string such as KDUMP_COMMANDLINE="", the default will be taken
automatically
> +from the '/proc/cmdline'. Most time, no need to modify it.
> +
> +-KDUMP_COMMANDLINE_REMOVE
> +
> +This option allows us to remove arguments from the current kdump command line.
> +If we don't specify any parameters for the KDUMP_COMMANDLINE, it will inherit
> +all values from the '/proc/cmdline', which is not expected. As you know,
some
> +default kernel parameters could affect kdump, furthermore, that could cause
> +the failure of kdump kernel boot.
> +
> +In addition, the option is also helpful when we want to make a debugging, we
make a debugging reads strange to me, maybe just say it's helpful to
debug the kdump kernel?
> +can use this option to reconfigure kdump kernel command line.
> +
> +For more kernel parameters, please refer to kernel document.
> +
> +-KDUMP_COMMANDLINE_APPEND
> +
> +This option allows us to append arguments to the current kdump command line
> +after processed by the KDUMP_COMMANDLINE_REMOVE. For kdump kernel, some
> +specific modules require to be disabled like the mce, cgroup, numa, hest_disable,
> +etc. Those modules may waste memory or kdump kernel doesn't need them,
> +furthermore, there may affect kdump kernel boot.
> +
> +Just like above option, it can be used to disable or enable some kernel
> +modules so that we can exclude any errors for kdump kernel, this is very
> +meaningful for debugging.
> +
> +-KDUMP_STDLOGLVL|KDUMP_SYSLOGLVLKDUMP_KMSGLOGLVL
> +
> +These variables are used to control the kdump log level in the first kernel.
> +In the second kernel, kdump will use the rd.kdumploglvl option to set the log
> +level in the above KDUMP_COMMANDLINE_APPEND.
> +
> +Logging levels: no logging(0), error(1),warn(2),info(3),debug(4)
>
> Kdump Post-Capture Executable
> -----------------------------
> --
> 2.17.1
>
--
Best Regards,
Kairui Song