I created a USB boot disk to install High Sierra with, and used it on my iMac. I think the boot disk wasn't created correctly, because disk images don't mount the way they're supposed to. I'm wondering if this is a permissions issue with /Volumes (which is easily fixed with Terminal), or something more serious (disk image handler corrupt?). The issue manifests itself when I try to mount a disk image. What happens is the disk image icon appears in the sidebar as normal, but clicking it tells me the original item cannot be found. I have to go into Disk Utility to unmount the phantom disk.
