System z Dumps
Unlike Kdump, the Linux on System z standalone dump tools don’t require reserved memory; they’re installed on a storage device and IPLing from that device triggers the dump process.
Note that some of the features described in the following might be available only on the latest Red Hat Enterprise Linux and SUSE Linux Enterprise Server distributions.
DASD and tape standalone dump tools: Standalone dump tools for DASD and channel-attached tape devices are available. The tools are written in Assembler and are loaded into the first 64KB memory that isn’t used by the Linux kernel.
System z standalone dumps use two tools from the s390-tools package: zipl prepares dump devices, and zgetdump copies kernel dumps from DASD or tape into a file system (see Figure 2).
These steps prepare partition /dev/dasdd1 on DASD 1000 for a standalone dump:
- Format DASD: dasdfmt /dev/dasdd.
- Create a partition: fdasd -a /dev/dasdd.
- Install the dump tool: zipl -d /dev/dasdd1.
After a system crash, an IPL from the DASD device creates the dump. Before the IPL, all CPUs must be stopped and the register state of the boot CPU saved by issuing the commands in Figure 3 on the VM console of the crashed guest. After rebooting the guest, the dump can be copied into a file system using zgetdump:
# zgetdump /dev/dasdd1 > /mydumps/dump.s390
It’s also possible to copy the dump to a remote system using Secure Shell (ssh):