Appendix: Creating Diagnostic Test Images

In uncommon situations a cluster administrator may wish to execute a self-contained diagnostic program as a compute node image. "Self-contained" means the diagnostic program itself functions as a kernel and does not need an initrd.

An example is the memtest86+ memory diagnostic, which can be downloaded from www.memtest.org:

# Download the latest compressed binary:
wget https://www.memtest.org/download/5.01/memtest86+-5.01.bin.gz

# Uncompress the downloaded file to expose the binary:
gunzip memtest86+-5.01.bin.gz

# Clone the DefaultBoot into a new boot configuration that consists of just the binary:
scyld-bootctl -i DefaultBoot clone name=MemtestBoot kernel=@memtest86+-5.01.bin

# Configure the desired node (e.g., n123) to execute that new boot configuration:
scyld-nodectl -i n123 set _boot_config=MemtestBoot

# And then reboot that node (with 'legacy' pxe booting!)
scyld-nodectl -i n123 reboot

Note

The current memtest86+ only works for legacy PXE booting, not for uefi PXE booting, so the administrator needs to change the target node's BIOS setting to legacy to boot memtest86+ -- and revert back to uefi if desired for normal ClusterWare compute node PXE booting.