How to Configure KDUMP on Oracle Linux 8 and 9
1). If the kdump package is not already installed on your system, install it:
# dnf install kexec-tools
2). With the proper administrative privileges, edit the /etc/default/grub file and set the crashkernel= option to the required value.
For example, you would reserve 64 MB of memory as follows:
crashkernel=64M
You can also set the amount of reserved memory as a variable by using the following syntax: crashkernel=range1:size1,range2:size2.
For example, you might set the memory as a variable as follows:
crashkernel=512M-2G:64M,2G-:128M
(Optional) If necessary, define an offset value for the reserved memory.
Because the crashkernel reservation occurs very early, some systems require that you reserve memory with a certain fixed offset. When a fixed offset is specified, the reserved memory begins at that point. For example, you would reserve 128 MB of memory, starting at 16 MB as follows: