cdio(1)
My older invocation of cdio stopped working from a user shell that I su'd to root. When I follow the FAQ with full paths it works. As noted in the FAQ, specifying the device is important, particularly if you have more than one.
https://www.openbsd.org/faq/faq13.html#burnCD
Code:
# cdio -f /dev/cd0c tao -s 8 full_path_to/sys.iso
I use optical media for backup, usually Ridata that I buy shrink-wrapped off Ebay. It has been years since I have made an aluminized coaster.