I would like to know if it possible to share an user profile if you have both 10.6 and 10.7 installed on the same machine (different partitions).

So far my experience was not a good one but maybe I did something wrong.

I am interested mostly in sharing iTunes library, Outlook 2011 database and other user setting.


You can specify the same home folder, but I'd suggest leaving them separate since you'd potentially have incompatible preference, cache, and other "Library" files between the two versions of OS X.

Perhaps symlink the corresponding preferences for the apps that you want to share data.

iTunes Library is easily shared, just hold the Option key when launching iTunes the first time to specify the library to open (it will remember it subsequently).

Since Office 2011 wants to use the Microsoft User Data folder within ~/Documents, you'll likely have to symlink this folder from one of the profiles.


In general reverting a user folder to a prior version of the OS is a world of hurt. In specific, mixing that pain with the pain of beta / unreleased / unfinished software can really foul things up. A serious effort is expended to make upgrade scripts so that your data can make the jump from 10.6 to 10.7 and there isn't any effort into making that reverse trip.

Once the newer OS touches the preferences, files, databases - it's a one way trip. Even a third party app uses API calls from the OS that can make internal caches and data stores incompatible. There are no scripts or undo on the upgrade to revert these changes and pull out the new items so that they work on the older version of the system. Running both systems will amplify this bad effect: go forward and change things, go back and break, go forward and change broken things, go back and break them in new and novel ways.

At best, you will get a nice warning from the program when it detects that the settings and data from a newer version can't run and the program will gracefully quit. At worst, data will be lost and/or corrupted.

Now - lots of things will still work (mostly) and you will get to learn a ton about how things are stored and how software behaved as it breaks.

If your goal is to learn and play, have at it! Seriously - it's a great learning exercise. Well over half of my most valuable knowledge of systems was gained from seeing them break, poking around to see how exactly it broke, disassembling and understanding the system, attempting to fix, failing and then reinstalling if it can't be fixed. This is a great way to learn what has changed under the hood between 10.6 and 10.7 preview assuming nothing will ever be used again and you don't mind walking away from the machine by erasing it and starting fresh.

For a machine you want to use for real work and data, it's a really bad idea.

  • I'll add a comment - What I do love to do in this case is to buy an external drive and install the new OS on the external drive. I'll boot to that drive leaving my important data on my internal drive and migrate that data to the "new" OS to play with for a day. I'm very careful to not do anything on the "new" OS that I can't export or save back to the old system. You can run for weeks like this to learn. Then erase the "new" and try again with the migrate when a bug arises. You're always a reboot away from your stable system with it's data safe and sound. – bmike Apr 21 '11 at 17:04
  • One word to this answer: yep. +1 – ConstantineK Apr 21 '11 at 17:27

If you can link them in a Terminal this should be possible

We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

  • 1
    So is drinking bleach :) – ConstantineK Apr 21 '11 at 20:35
  • It is not impossible to link the in a Terminal and it would not screw anything up – luca590 Apr 21 '11 at 20:38
  • So apple.stackexchange.com/questions/12571/… is wrong then? Also drinking bleach is possible, just not recommended. – ConstantineK Apr 21 '11 at 20:57
  • your right but this is recommended, and no he's not wrong im offering more than one solution considering you havnt offered any? – luca590 Apr 22 '11 at 0:57

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