Boot Mac OSX 10.10 from an external USB harddisk that was prepared by another machine.

Short answer: yes, doable!  I can boot Mac OSX 10.10 from an external USB harddisk that was prepared by another machine.

I have a MacMini 2009 edition in the office and a MacMini 2012 Server at home, and I have a USB 3.0 portable hard disk.  My goal was trying to have portable OSX 10.10 environment that I can use both at home in the office.

So I spent sometime to set up the portable harddisk (which I explained everything in my last blog), and then I use my office MacMini 2009 to setup OSX 10.10 in the MacJournal Extended partition.  And then I install all sorts of software in it.  At night I plugged this harddisk to my home MacMini 2012 Server, boot up the MacMini 2012 with an Windows 8.1 on it (bootcamp), and tried to use the System Tray BootCamp applet change the bootup partition.  However it kept rebooting to Windows 8.1.

Eventually I hold the ALT key during bootup and force it to boot from the OSX on USB 3.0 portable harddisk.  It worked.  I then set the startup partition to the OSX 10.10 on the hard disk.  I didn't have time to try it out (by reboot) afterward, which I will probably do later today.  But at least I know there's a way to boot from an OSX partition that had been prepared by another machine.

BTW, I was NOT able to use SyncToy to sync a huge amount of file between a network location to a OSX drive directory on Windows 8.1.  I will try syncing to a exFAT partition and see if I get better result.