As I’ve said in a previous post, nearly the exact same process (that is, editing the systemversion.plist file) is used for this as for changing the iPhone OS version, since OSX and iPhone OS are based on the same core, but I’m writing this with more desktop OSX-specific steps and screenshots.
I suppose the question would arise, “Why would one want to do this?” On Leopard, it is incredibly useful in situations where one may wish to install software that claims to require an update that you don’t want to install. I’ll be demonstrating on Snow Leopard, but the procedure is the same on both. In my demonstration, I will be changing the version number from 10.6.2 to 10.7.0. This has no practical use, but will suffice for demonstration purposes.
1. Mac OS X
2. A basic knowledge of Terminal
1. Open Terminal.
2. Type sudo nano -w /System/Library/CoreServices/SystemVersion.plist
Does the file path look familiar from my last tutorial?
3. Press Enter. You will be prompted for your password. Type it in. You won’t see it on your screen. Press Enter again.
4. Use the arrow keys to navigate to the end of the 10.6.2 under ProductUserVisibleVersion and erase the version number. Enter in a version number of your choice.
5. Repeat for the version number displayed under ProductVersion.
6. Press X (Control-X) to exit. It will ask you if you wish to “save modified buffer.” Press y. It will then ask for a file name to write. Press Enter to accept the default.
7. Exit Terminal.
Needless to say, to reverse this process, just follow the steps again, changing the version number back to the original system version.