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
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)
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
Initial dump space	Memory	Dump device	File system of the KVM host	Spool device
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 -c from a new Linux instance
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
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
Dump aspect	Live-system dump with zgetdump
Preparation	None
Dump trigger	Initiated by operator: zgetdump invocation
Initial dump space	Memory
Accessing the initial dump	Through /dev/crash
Copying the initial dump to the final dump store (and releasing the initial dump space)	Copied from the current Linux instance to any available storage
Optional: Filtering the initial dump	Not recommended