Booting an iMac using a Macbook Pro's internal disk Suppose I have an iMac and a Macbook Pro. My Macbook Pro is my primary workstation, and when I switch to the iMac I would like my environment to be exactly the same in order to facilitate switching between the two during the day.

I read somewhere that it's possible to make a Macbook Pro behave as a simple external disk and connect it to another device that can read it. This means it might be possible to connect the Macbook Pro to the iMac and let the iMac boot from the Macbook Pro's disk, effectively providing the same environment on both machines.

Is this sort of thing possible? Will the two devices operate well while trying to boot from the same startup disk?
Depending on your Macs you might use the FireWire/Thunderbolt target-disk mode.  

Apple-KB:  


  If you have two Mac computers with FireWire or Thunderbolt ports, you can connect them so that one of them appears as an external hard disk on the other. This is called “target disk mode.”
  1. Connect the two computers with a FireWire or Thunderbolt cable.
  2. Start up the computer to be used as a disk in target disk mode:
  - If the computer is off, start it up while holding down the T key.
  - If the computer is on, choose Apple menu > System Preferences, click Startup Disk, and then click Target Disk Mode.
  When the computer has started up, a disk icon appears on the desktop of the other computer.
  3. Transfer files by dragging them to and from the disk.
  4. Eject the disk by dragging its icon to the Trash.
  While you drag, the Trash icon changes to an Eject icon.
  5. On the computer you used as a disk, push the power button to shut it down, and then disconnect the cable.


The target-mode-Mac will act as an additional external harddrive. You may use that as a start volume though and consequently have the MacBook Pro environment with a bigger monitor and better sound assumed the target-mode-Mac is your MacBook Pro.

But the environments on the two internal drives still differ. Example: If you add a user in the above case you will add it to the MacBook Pro System and not to the iMac System.

The only way to have identical environments is to clone one to another.