As I excuse in Installing Lion : What you need to know , one of the requirements for installing Lion is that you already have Snow Leopard ( Mac OS X 10.6 ) version 10.6.6 or after installed . The main virtual reason for this essential is that Lion is usable only via the Mac App Store , and the Mac App Store debuted in Mac OS disco biscuit 10.6.6 . In other parole , you need Snow Leopard just to buy and download Lion .

But once you ’ve got your written matter of Lion , can you install it onto a Mac or a hard drive containingLeopard(Mac OS ten 10.5 ) ?

The software permission you agree to when you install Lion states that you could “ download , install , expend and run for personal , non - commercial-grade use , one ( 1 ) transcript of [ Lion ] directly on each Apple - branded computer running Mac OS X Snow Leopard or Mac OS go Snow Leopard Server … that you own or check . ” In other language , if your Mac shipped with Snow Leopard , you may instal Lion on it . If your Mac embark with Leopard , but you subsequently purchased Snow Leopard for , and installed it on , that Mac , you’re able to set up Lion on it . If you did n’t purchase Snow Leopard , you ca n’t install Lion .

Those situations are jolly open . But what if , for example , you ’ve got a family - pack permit for Snow Leopard , and you ’ve got a Mac that shipped with Leopard but that you never raise to Snow Leopard ? Assuming that Mac is compatible , the Lion license concord says you ca n’t elevate to Lion until you first install Snow Leopard .

( This is just one scenario — I can conceive of a telephone number of situations in which you might have Leopard on a Mac or an outside hard drive , along with a valid permission for Snow Leopard , and you ’d rather not take the interim step of installing Snow Leopard just to upgrade to Lion . Having performed this two - stone’s throw climb many time while explore our various Lion - installation articles , I can order you that it ’s a literal hassle . )

But net ball take a tone back . While theletterof the police say you need to set up Snow Leopard before installing Lion , thespiritof the law seems to be that a particular Mac just necessitate alicensefor Snow Leopard before you could install Lion on it . In other words , in our view , you should be well within your right to instal Lion on any of your computers for which you have avalid , current Snow Leopard license — even if you do n’t instal Snow Leopard on it first .

So then the enquiry becomes whether there are anytechnicalreasons you ca n’t set up Lion over Leopard . Based on our examination , the Lion installer refuses to install Lion onto a driving contain Leopard ( 10.5 ) ; in fact , it turn away to instal on any drive go a version of Mac OS cristal below 10.6.6 . It will , however , install onto a white drive , so Lion intelligibly does n’t ask any of Snow Leopard ’s files or setting .

You may be thinking , “ It will install onto a blank parkway ? Then I ’ll just simulate the installer to my Leopard - equipped Mac , connect an empty hard drive , put in Lion there , and then apply Migration Assistant to move my file over to it . ” Alas , while the Lion installer will freely install Lion onto a blank campaign , the installer itself must be run from within Snow Leopard or Lion .

So howcanyou install Lion over Leopard ? There are three manner : the official way , the brute - power method , and the quick - but - tekki way of life . Whichever method you opt , you should — as with any OS installation — be sure to have an up - to - date , tested computer backup of your drivebeforeyou lead off .

The official way

As I explained above , Apple ’s prescribed policy is that if you need to install Lion onto a Mac or a tough drive containing Leopard — seize , of trend , the Mac in interrogative sentence meetsLion ’s organization requirement — you must first intall Snow Leopard andtheninstall Lion . This work , it ’s pretty easy to do — if a bit time - consuming — and it obtain the Apple seal of approval .

The brute-force method

What if you do n’t want to install Snow Leopard first , or if you do n’t have your Snow Leopard disk handy ? ( I ’m not being coy here — perhaps you ’ve misplaced it , or mayhap you ’re on the road and you ’ve receive your Mac ’s original [ Leopard ] magnetic disk with you as an emergency boot disc , but you do n’t have your Snow Leopard upgrade phonograph record . )

As I mentioned above , the Lion installer will let you install Lion onto abaredrive when the installer itself is run under Snow Leopard or Lion . So as long as you have a good computer backup ; a 4GB - or - larger thumb drive or external drive ; and either memory access to a Mac running Snow Leopard or Lion , or an already download copy of the Lion installer , you’re able to perform a moment of installer razzle-dazzle - dazzle . You just erase your Mac ’s drive , instal Lion onto it , and then import all your data from your support . ( If this sound a draw like aclean install , that ’s because it ’s essentially the same appendage . ) Here ’s are the steps to take :

check that you have an up - to - escort backup — either a Time Machine stand-in or a clone musical accompaniment using a utility such as SuperDuper or Carbon Copy Cloner — of your Leopard Mac ’s hard driving . ( For this use , I recommend a clone . ) Be certain totestthis backup to avow that it has your latest data : In the case of a Time Machine backup , try out restoring some authoritative data from the championship ; in the case of a ringer backup , flush from the clone to verify it boots and that it contains all your data .

habituate the Snow Leopard or Lion computer to download the Lion installer from the Mac App Store . ( If you ’ve already generate your copy of the Lion installer , vamoose this measure . )

produce a bootable Lion - installer ride using the pedagogy in How to make a bootable Lion install saucer or campaign .

bring up your Leopard Mac from that new Lion install drive . When you do so , you ’ll find yourself with a screen called Mac OS X Utilities with several options . ( This is the same screen you ’ll see if you bring up your Mac inrecovery mode . )

Select Disk Utility and click Continue , then employ Disk Utility to efface your Leopard Mac ’s internal drive . To do so , choice that motor on the left , click Erase on the right field , choose Mac OS X Extended ( Journaled ) from the Format pop - up menu , and click Erase . admonition : This step rub out all the data on your Mac ’s punishing driving , which is why you needed that backup !

When the erase subroutine is finished , resign Disk Utility to get back to the Mac OS X Utilities screen .

Select Reinstall Mac OS X and click Continue to launch the Lion installer and put in Lion on your Mac ’s national drive .

After your Mac restarts , induction refinement , and you carry on through the setup process , watch for the Transfer Information To This Mac blind . You ’ll use the third selection , From Time Machine Or Another Disk , to channelise all your files from your championship to your new installation of Lion .

When the transference process is finish , you ’ll be able-bodied to lumber in to Lion with all your account and data intact .

The quick-but-techie way

If you ’re well-situated diving into the type O and editing a plist file , this is the loyal way to install Lion over Leopard , although , as with the former method , you ’ll need to be able to boot from a Snow Leopard or Lion drive to launch the installer .

As I refer above , the Lion installer decline to set up the operating system on a Leopard Mac . But how does the installerknowyour drive contains Leopard and not Snow Leopard ? It turns out that the installer just fit a particular file—/System / Library / CoreServices / SystemVersion.plist — on the terminus disk to check the version of OS X presently installed on that disk .

Which means that if your Mac is guide Leopard , and you ’re feeling adventuresome , you could edit the SystemVersion.plist file so that it claims you ’re running , say , 10.6.7 . The Lion installer — which will still postulate to be head for the hills on a Mac running Snow Leopard or Lion — will then put in Lion over Leopard without the flimsy charge . Here ’s how to do that :

On your Leopard - fit Mac , voyage to / System / Library / CoreServices .

Using a textbook editor that lets you enter an admin - user name and password to edit arrangement - level files — such as thenon - Mac App Store versionofTextWrangler — open SystemVersion.plist .

site the ProductVersion key ( not the ProductUserVisibleVersion key fruit ) . Just below that is a chain of identification number point the OS adaptation ; for example , on a Mac unravel OS X 10.5.8 , it will read10.5.8 .

Change that issue to 10.6.6 ( or 10.6.7 or 10.6.8 ) , save the file ( provide your admin - level username and parole when prompted ) , and then shut down your Mac .

last , you ’ll want to reboot your Mac from a private road draw Snow Leopard or Lion that also contains the Lion installer . If you ’ve create a bootable Lion install disk or drive , just boot your Mac from it , and when the Mac OS X Utilities screen appears , use the Reinstall Mac OS X option to install Lion on your Leopard drive . You could rather boot your Leopard Mac from an international drive hold back Snow Leopard or Lion , and then melt the Lion installer from there . Another option , if you ’ve got two Macs with FireWire , is to boot the Leopard Mac into Target Disk Mode and relate it to your Snow Leopard or Lion Mac , and then execute the Lion installer .

Whichever overture you take , when you ’re done , you ’ll have Lion on your previously Leopard Mac .

Updated 7/21/2011 , 12:30pm , to fix an error in Step 5 of the “ quick ” procedure .