HowTo revert new MacBook Pro, Mac Pro or iMac to Snow Leopard
Hi all,
the following instructions were provided to me by our Apple Enterprise tech, and I've successfully performed these steps on a newly purchased MacBook Pro.
Please note the following - as of 15 Aug 2011:
- this technique will work on new MacBook Pro, Mac Pro or iMac computers UNTIL Apple modifies the hardware in these computers
- this technique will NEVER work on currently shipping MacBook Air or Mac Mini computers
- this configuration of Snow Leopard installed on a computer that shipped with Lion is not supported by Apple Support. It is entirely possible that after a trip for an AppleCare support incident, or the Apple Genius Bar, that the computer will return with Lion installed.
with these caveats, here are the step-by-step instructions:
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HowTo - NetRestore - Install Mac OS X 10.6.8 on new Mac delivered with Mac OS X 10.7.0
note: this only applies to Macbook Pro, Mac Pro, and iMac computers that originally shipped with Mac OS X 10.6.x.
Current Macbook Air and Mac Mini computers cannot be downgraded.
Required resources:
- another computer, running Mac OS X 10.6.8
- spare external disk
- Snow Leopard installation disc (Mac OS X 10.6.0 or 10.6.3 Box Set)
- Snow Leopard 10.6.8 Combo image file (download from Apple Support Downloads page)
- System Image Utility 10.6.8 (download Mac OS X 10.6.8 Update Combo v1.1.dmg from Apple Support Downloads page)
Procedure:
A. Create the NetImage:
1) mount the base source image (Mac OS X 10.6.3.dmg - created from Box Set Installer)
2) launch System Image Utility (from Server Admin Tools)
3) when source (from mounted image) appears in SIU screen, click Custom button
4) drag "Customize Package Selection" from Automator Library window to location
between existing "Define Image Source" and "Create Image"
5) drag "Add Packages and Post-Install Scripts" from Automator Library to location
between "Customize Package Selection" and "Create Image"
6) in the "Customize Package Selection" section:
a) expand the "Mac OS X" triangle
b) select options desired
c) collapse the "Mac OS X" triangle
7) mount the appropriate update image (Mac OS X 10.6.8 v1.1 Combo.dmg)
8) copy the MacOSXUpdCombo10.6.8.pkg package to a new local directory (Desktop/parts/)
9) drag the MacOSXUpdCombo10.6.8.pkg icon from local directory to the
"Add Packages and Post-Install Scripts" section of the SIU window
10) in the "Create Image" section:
a) select the type "NetRestore"
b) set the "Installed Volume:" field to "Macintosh HD" (no quotes, can be any name)
c) select the "Save To:" location
(will be faster to a second local internal disk)
(not faster to another partition on the same disk)
d) set the "Image Name:" field to "Snow Leopard 10.6.8 NetRestore"
e) the fields "Network Disk:", "Description:", and "Image Index:" don't
matter unless one is going to use results on a NetBoot Server
11) click the Run button
12) when the dialogs appear, ignore the text and click OK for proper completion
Dialog text: "Image creation in progress.
Cancel the image creation to proceed"
B. Post-process to create Restore Image:
1) find the directory created in the above process, named as in A.10d above
(Snow Leopard 10.6.8 NetRestore.nbi)
2) in this directory are three files:
- i386
- NBImageInfo.plist
- NetInstall.dmg
3) mount the NetInstall image (double-click the NetInstall.dmg file)
4) navigate into the Contents of the package, to: System/Installation/Packages/
5) copy the System.dmg file out to desktop or other work location
6) rename System.dmg to meaningful name, such as "Snow Leopard 10.6.8 System.dmg"
7) copy this .dmg file to external, bootable, Snow Leopard 10.6.8 system disk (install in /Users/Shared/)
C. Install Snow Leopard 10.6.8 on new MacBook Pro or Mac Pro
via command line:
1) boot MacBook Pro or Mac Pro from external source prepared in B.7
2) open Terminal
3) find the restore target device specification
a) run the command "diskutil list"
b) look for a 650 MB partition, labelled "Recovery HD" (likely disk0s3)
c) the target partition should be immediately prior to the "Recovery HD" partition
d) for a new computer with a 500 GB drive, this partition should be
labelled "Macintosh HD", with a size of 499.2 GB
e) make note of it's Device Identifier, likely disk0s2
4) issue the following asr (Apple Software Restore) command
sudo asr restore --source "/path/to/restore.dmg" --target /dev/disk0s2 --erase
(replace "/path/to/restore.dmg" with the path to the location and name used in step b.7)
5) this process proceeds and completes quickly, about 3-5 minutes. This is due to
the "--erase" parameter; it indicates a block-copy operation
If the process seems slow, likely the "--erase" option was omitted and
the copy is being done as a file-copy operation. Quit (ctl-c) and
examine the command used...
via DiskUtility GUI:
1) boot MacBook Pro or Mac Pro from external source prepared in B.7
2) launch /Applications/Utilities/DiskUtility.app
3) select the computer hard drive (typically "Macintosh HD")
4) click on the "Restore" tab
5) click on the "Image..." button to specify the "Source"
6) navigate to /Users/Shared/ and select the "Snow Leopard 10.6.8 System.dmg" file
7) drag the computer hard drive volume (Macintosh HD) to the "Destination" field
(note: grab the volume, not the disk!!)
8) enable the "Erase destination" checkbox
9) click the "Restore" button
10) in the ensuing "Are you sure?" dialog, click the "Erase" button
11) authenticate with the local admin credentials
Apple Tech recommends leaving the Restore partition alone, and installing in the "Macintosh HD" partition only
commands to know:
- asr
- diskutil (diskutil -list to see partitions)
- hdiutil