[jpstewart]

I started with a simple "mount SGI-Nintendo-Ultra-64.iso" and got that error.
After reading your reply, I tried "mount -t efs -r SGI-Nintendo-Ultra-64.iso" and got the usage line with all the options listed, which makes me think I'm not using the correct syntax, but I don't know what I'm doing wrong.

You didn't specify a mount point. E.g.,

Code:

mount -t efs -r SGI-Nintendo-Ultra-64.iso /foo

Use any existing (and preferably, empty) directory in place of /foo.

Also, I'll re-iterate that I'm not a NetBSD expert so I don't know if that is sufficient for a loopback mount. On Linux you'd also need '-o loop' in there (as shown in jan-jaap's post) but that is not the right syntax for NetBSD. You may need another option or you may need a different command entirely to setup a loopback device first (equivalent to losetup on Linux). Perhaps somebody with NetBSD knowledge will weigh in on that.