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 Linux 64-bit ISO: mt86plus_6.01_64.iso.zip

# Uncompress the downloaded file to expose the ISO:
unzip mt86plus_6.01_64.iso.zip

# Mount the ISO
sudo mkdir -p /mnt/mt86plus_6.01_64
sudo mount mt86plus_6.01_64.iso /mnt/mt86plus_6.01_64 -o loop

# Create a new boot configuration that consists of just the efi binary:
scyld-bootctl create name=Memtest_6.01_Boot kernel=@/mnt/mt86plus_6.01_64/EFI/BOOT/bootx64.efi

# Configure the desired node (e.g., n123) to execute that new boot configuration:
scyld-nodectl -i n123 set _boot_config=Memtest_6.01_Boot

# Ensure that you have a method to view serial output from that node.
# For example, if serial output for node n123 uses ttyS1:
scyld-bootctl -i Memtest_6.01_Boot update cmdline="console=ttyS1,115200"

# And then reboot that node.
scyld-nodectl -i n123 reboot

Note

memtest86+ version 6.01 works for both legacy and uefi PXE booting.