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10.5: Bypass the installer's system requirements check Install
Apple usually weeds out a few machines with new versions of OS X, but 10.5 is the first release I'm aware of that will exclude a larger number of machines from being able to run the new OS. For example, my trusty G4 fails to meet the minimum processor requirements -- it has enough RAM to run 10.5, but the installer prevents me from installing. I doubt I'll be alone here.

All is not lost, however, as it is possible to modify the file that checks the machine specs and decides if 10.5 can be installed.

We first need to restore the 10.5 DVD onto a read/write media. I typically use an external FireWire drive for this. It is as simple as attaching the drive and inserting the DVD into the machine. Then launch Disk Utility and select the drive/partition to restore the DVD onto. Drag the DVD to the source area and the drive/partition to the destination area, and start the restore.

If this was 10.4, we could simply edit the Distribution file in the mpkg file, but Apple has changed things -- they now use xar to compress the mpkg file, so we'll need to decompress the mpkg file and then edit the Distribution file.

Here is what needs to be done:
  1. Download xar (tar and gz file).
  2. Expand the tar.gz file and open terminal and cd into its directory.
  3. Issue the folowing commands, pressing Return between each one and then waiting for its completion (Developer Tools required):
    $ ./configure
    $ make
    $ sudo make install
  4. Check that the install is in the right location (/usr » local » bin » xar) by issuing which xar; it should return the aforementioned location.
  5. Copy the required mpkg to the desktop. For 10.5, the package we want is in /System » Installation » Packages/ folder on the drive with 10.5, and is called OSInstall.mpkg.
  6. Create a new folder on the desktop, eg; OSInstall. Go into Terminal and cd into this folder, then issue the following command to decompress the mpkg to the folder:
    $ xar -x -f /path/to/OSInstall.mpkg
  7. Go into the OSInstall folder, and you'll see a Distribution file and Packages folder.
  8. Open the Distribution file in a text editor, for example I use BBEdit. It's an xml script, so you can just edit it. Look for minRam and the processor speed requirments, and change these, and any other options which could prevent install on your setup. Save the changes.
  9. Issue the following command to compress the files back into xar'd mpkg file: xar -c -f OSInstall.mpkg *.
  10. The OSInstall folder should now have a new OSInstall.mpkg file in it. We then need to copy this new file into /System » Installation » Packages folder on the drive with 10.5. Firstly I'd rename the existing OSInstall.mpkg so we have a copy of it, so cd into the /System » Installation » Packages folder on the drive with 10.5, and issue the following command in Terminal:
    $ sudo mv OSInstall.mpkg OSInstall_orig.mpkg
  11. We then need to copy over the new package, so issue the following command in Terminal:

    sudo copy /path/to/OSInstall.mpkg /Volumes/name_of_105_disk/System/Installation/Packages/OSInstall.mpkg
Now that all remains is to go into the Startup Disk preference pane and select the drive we copied 10.5 to, boot from that drive, and you should then be able to install without issues.

One major thing worthy of note. Do not try and run the installer on a machine with 256MB or less of RAM, in fact, you probably want at least 384MB RAM. I did try 256MB and found the installer simply would not complete, and this was on a machine whose processor was within the the range specified by Apple.

[robg adds: I have heard from a friend who used this technique to install Leopard on a G4 Cube, and he said that it runs "just fine," though I'm not sure of the details behind that statement.]
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10.5: Bypass the installer's system requirements check | 17 comments | Create New Account
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10.5: Bypass the installer's system requirements check
Authored by: vorlonwarrior on Nov 01, '07 07:51:07AM

One additional thing to mention, I'd not bother trying to install 10.5 on a G3 (I had not attempted this when the hint was submitted). Even though you can modify the Distribution file to remove the "Fail on G3" check (it's checking for "hw.vectorunit" and if false, it will not install - I think this is a check for Altivec which the G3's don't have, but I could be wrong), once you have installed and rebooted the machine will sit at the Grey Apple screen with the spin icon for, well, I gave up after four hours of it sitting there, so I'd say it's probably safe to assume it won't ever progress.



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10.5: Bypass the installer's system requirements check
Authored by: scolson on Nov 01, '07 08:29:49AM
You beat my post! You can actually do this without downloading and using xar directly. Once you get to the OSInstall.mpkg file, simply:
  1. Right click and open it with "Flat Package Editor.app" (in Leopard)
  2. Drag the "Distribution" component out to your desktop
  3. Edit and save it with a standard text editor (I used BBEdit)
  4. Drag it back in to the mpkg
  5. Delete the old version from the mpkg
  6. And save!
Either way people go about it, it is nice for all those people with flat panel iMacs to not have to upgrade over a lousy 67 Mhz.

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10.5: Bypass the installer's system requirements check
Authored by: markuswarren on Nov 01, '07 09:56:45AM

You'd need to install the developer tools first to get Flat Package Editor.

Looking at it, this might be a far easier way of editing it, as I did have a problem with xar on my iBook.



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10.5: Bypass the installer's system requirements check
Authored by: ajmas on Nov 02, '07 08:05:36AM

Note, that from I can tell 'Flat Package Editor.app' is part of PackageMaker.app, that comes with the Developer tools ( XcodeTools.mpkg on the install disk).



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10.5: Bypass the installer's system requirements check
Authored by: lonepalm on Nov 01, '07 09:36:24AM

Will this solve the problem where my Quicksilver w/Dual 1.6 GHz G4 will not let me see the 3rd and 4th video effects windows in iChat ?



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10.5: Bypass the installer's system requirements check
Authored by: markuswarren on Nov 01, '07 10:01:56AM

I seriously doubt it would. This hint is to allow you to install 10.5 on Machines that Apple does not officially support. The reasons for Apple not supporting certain machines lies partly in the fact that 10.5 will be using technologies that require a fair bit of power, which lesser machines cannot handle.

The windows in iChat you mention contain the funky backdrop effects, which would certainly require a poweful machine and iChat is probably detecting your machine specs don't match what it needs and disables them.



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Another method
Authored by: frgough on Nov 01, '07 11:08:27AM

I installed Leopard on an 800 MHz "lamp" model iMac using the tried and true firewire target disk mode from a supported machine (in this case a PowerBook G4).

Performance is excellent, but Apple says unsupported for a reason. Screen sharing in iChat will not work, and if you sleep the iMac, the video will be completely garbled and unusable on wake. Those are the only two things I've discovered in the past several days of use.



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Sleep Deprived Video on 800 MHz iMac
Authored by: Criss_Hyde on Nov 01, '07 04:54:10PM

I have had a similar experience installing to an 800 MHz iMac in target disk mode. Everything looked good until what I call "sleep deprived video" kicked in. I have disabled several means that invoke sleep. I haven't tried the iChat yet. /criss



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Another method
Authored by: TvE on Nov 02, '07 01:05:19AM

I did the exact same thing since I will use that machine as my new music jukebox, the inability to be able to sleep (or perhaps actually to be able to get the video back after wake from sleep!) is actually not a good thing for a machine that really could benefit from allways being on, but sleeping most of the time.


I am waiting + hoping that some time soon some clever head will be able to find a workaround so the machine can sleep+wake so I can save a lot on my electric bill ;-)



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10.5: Bypass the installer's system requirements check
Authored by: olsen on Nov 01, '07 12:43:35PM

I installed Leopard on my PowerBook Titanium @ 800 MHz. However, iChat wont let me use my iSight Camera. Any hint how I can make it work again?

---
Mac Gamer



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10.5: Bypass the installer's system requirements check
Authored by: montylee on Nov 02, '07 12:12:58AM

Any way to do this without having the Developer's Tools (listed as required above)?



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10.5: Bypass the installer's system requirements check
Authored by: Mato on Nov 02, '07 08:53:19AM

I've done this to instal Leopard on a G4 2x500 mhz, instal went fine (I used an internal drive) but impossible to startup again, it just stays forever on the startup grey apple ... any clue ? thanks :)

---
You dont have to swim faster than sharks, just faster than the guy next to you



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10.5: Bypass the installer's system requirements check
Authored by: sunwolf48 on Nov 27, '07 09:11:21PM

I haven't tried it yet but the new version of Pacifist should also give you easy access to the files in the package. Pacifist is a great tool that I was more than happy to pay the small shareware fee for. <Disclaimer>I have no fiscal interest in Pacifist nor do I know the developer (but he does great work!)</Disclaimer>



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10.5: Bypass the installer's system requirements check
Authored by: ajole on Dec 22, '07 02:06:04PM

need to some help. admit I am a novice from a MAC perspective. Following instructions in your posting, download xar, install xar, install developer tools, cd to xar location and run configure, make, sudo make install. All seems to work - no errors reported. issue which xar and "no xar in /bin /sbin /usr/bin /usr/sbin" is the listing I get back. Any help would be greatly appreciated



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10.5: Bypass the installer's system requirements check
Authored by: chleuasme on Dec 23, '07 06:46:12AM
add /usr/local/bin to your PATH ;-)

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10.5: Bypass the installer's system requirements check
Authored by: GhettoSoak on Nov 27, '08 10:41:29PM
G'day. The site listed below holds all your answers, and it is entirely easier than the trick here. I'm sure that what's on this page works equally as well; but this is exceedingly easy. Truth be told, there _is_ more than one way to skin a cat. Enjoy.

http://lowendmac.com/osx/leopard/openfirmware.html

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The Easiest Solution
Authored by: kd8cyb on Feb 03, '10 07:21:05PM
It is so much easier just to edit the plist that Installer.app reads:
sudo pico /System/Library/CoreServices/SystemVersion.plist
Change, e.g.,
	<key>ProductUserVisibleVersion</key>
	<string>10.5.8</string>
	<key>ProductVersion</key>
	<string>10.5.8</string>
to
	<key>ProductUserVisibleVersion</key>
	<string>10.6</string>
	<key>ProductVersion</key>
	<string>10.6</string>
if you want to fool Installer.app into thinking you have OS 10.6.

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