Dump methods compared

The process for preparing a dump device and obtaining a dump differs for the available dump methods.

Table 1. Comparing the dump methods
Dump aspect	kdump	Stand-alone tools	virsh dump	VMDUMP	Live-system dump with zgetdump
Preparation	Reserve memory with the `crashkernel=` kernel parameter Load the kdump kernel and the initial RAM disk into the memory of the production system. Use kexec or `systemctl start kdump`	Write the stand-alone dump tool to the dump device (zipl) Define the panic shutdown action (dumpconf)	None	Define the panic shutdown action (dumpconf)	None
Dump trigger	Automatic: Kernel panic Initiated by operator: PSW restart	Automatic: Kernel panic Initiated by operator: IPL of the dump device	Automatic: Kernel panic Initiated by operator: virsh dump invocation	Automatic: Kernel panic Initiated by operator: z/VM® CP VMDUMP command	Initiated by operator: zgetdump invocation
Initial dump space	Memory	Dump device	File system of the KVM host	Spool device	Memory
Accessing the initial dump	Through /proc/vmcore from the kdump instance (automatically done by kdump initrd)	Using zgetdump from a new Linux® instance	Available as a dump file on the KVM host	Using vmur from a new Linux instance	Through /dev/mem
Copying the initial dump to the final dump store (and releasing the initial dump space)	Copied from the kdump instance to any available storage (automatically done by kdump initrd)	Copied from the new Linux instance to any available storage	Copied from the KVM host to any available storage	Copied from the new Linux instance to any available storage	Copied from the current Linux instance to any available storage
Optional: Filtering the initial dump	Using /proc/vmcore and makedumpfile on the kdump instance (automatically done by kdump initrd)	Using zgetdump and makedumpfile on the new Linux instance	makedumpfile on the KVM host	Using zgetdump and makedumpfile on the new Linux instance	Not recommended