| Old Mainframe story... We had a VM/370 system with 8 Meg of memory used by 82 programmers.
VM/370 used virtual machines, one per programmer. The virtual machines were faithful
copies of the hardware. I was a systems programmer. In the virtual machine you could issue meta-commands such as
'shutdown' by putting the prefix "#cp shutdown". The prefix "#cp" could be changed at boot. Being curious I tried booting VM/370 in a virtual machine. The embedded VM/370 could then
create sub-virtual machines. Which, of course, raises the question... Will VM/370 boot
in one of the sub-virtual machines? Well, it certainly worked. I set the command prompt
to be "?cp" in the sub-virtual machine. Which raises the question... Will VM/370 boot in the sub-virtual machine? Well, it
certainly worked. The command prompt prefix was "@cp". Rise, Repeat... I was 8 levels deep and it still worked. Time to get back to work.
So I typed "#cp shutdown" instead of the latest chosen command prompt... I had absolute priviledge on the real hardware so "#cp shutdown" was executed by
the real, main VM/370 image. Which promptly shutdown the real machine. Of course, only I and my co-worker systems programmer knew what actually caused
the outage. |