Ask Different is a question and answer site for power users of Apple hardware and software. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I would like to have a (Mountain) Lion VM that I configure in a specific way, and store that in a particular place on the the system hard drive. This is simple enough.

However, I would also like VMWare Fusion to not write to that VM disk (making it essentially read-only), but only store the delta of the changes in a particular file that I specify. I would be ok using Fusion's snapping functionality if it can provide this feature. I'd also be willing to look into other virtualization solution, but already own Fusion.

My ultimate goal for this is: I'd like to have the delta stored on a mounted ramdisk (tmpfs).

Is this possible?

share|improve this question

Regarding the mounted ramdisk (tmpfs), it is possible, see some example:

$ hdid -nomount ram://256000  # 256000 (sector) * 512 (bytes/sector)
$ newfs_hfs /dev/disk1
Initialized /dev/rdisk1 as a 125 MB HFS Plus volume
$ mkdir /tmp/space
$ mount -t hfs /dev/disk1 /tmp/space
$ umount /tmp/space/
$ hdiutil detach /dev/disk1 
"disk1" unmounted.
"disk1" ejected.
share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.