Not supported of course, but Parallels posted blog showing High Sierra running in Parallels:
Here is a screen grab in case they pull the article:
We've been trying to get this to work, but haven't been successful.
So install consistently fails, it can't get past drive verification.
So we know, not supported, but, they blogged that it is (or was?) possible.
Anyone been able to get this to work?
PS, not for nothing but the much superior VMware Fusion Pro 8 does this without breaking a sweat...but I digress...not an option here unfortunately.
You won't be able to run Content Caching on a virtual machine. This action has never been supported on previous versions of macOS, but is explicitly disallowed on macOS High Sierra.