Installing OSX (Snow Leopard) + Linux (Slackware 13.37 x86_64) on a GUID/GPT disk, with Software RAID enabled (ICH8R) - Part 2

With both the iBoot CD and the OSX installation USB key rearing to go (see previous post), it's time to insert them both, and reboot, while making sure the CD/DVD drive is selected as your boot device. After a while, the iBoot boot selection screen should pop up, and provide you with the option to select "Mac OSX Install DVD" to boot from (which is actually our USB key) to start the installation process. NB: the name may be truncated, but if this is your first OSX install, just make sure you pick up the icon wit the Apple logo, as there should be only one.

Now, if your SATA controller was set to AHCI, or if you were using a JMicron SATA port, your target hard drive would likely be detected by the installer and you could actually proceed with the installation.
But of course, that wouldn't teach you how to add support for custom hardware on the fly, such as RAID SATA controller, would it, so where's the fun in that? Plus if you're reading this guide, you're trying to get an ICH controller in RAID mode supported.

In our case, if we try to iBoot our USB key, the installer won't see our target disk at all, so we need to address that on the USB key. The nice thing about our USB key procedure is that we can add AHCI support on the fly, and the producedure highlighted below should actually work for any SATA RAID controller (ICH9R, nVidia, whatever) that supports AHCI passthrough, not just ICH8R.

What's the big deal with AHCI vs RAID anyway?

As it turns out not much. The thing is, even in RAID mode, an ICH controller such as the one we use does AHCI passthrough. So why does the OSX installer see the disk in AHCI mode, but not in RAID mode?
Glad you asked. This is best illustrated by looking at the output from Linux's lspci both in BIOS AHCI mode and in BIOS RAID mode.

For the P5B Deluxe, here is what lspci -nn reports for our SATA ICH8R controller in AHCI mode:

00:1f.2 SATA controller [0106]: Intel Corporation 82801HR/HO/HH (ICH8R/DO/DH) 6 port SATA AHCI Controller [8086:2821] (rev 02)

And here is the same, but in RAID mode:

00:1f.2 RAID bus controller [0104]: Intel Corporation 82801 SATA RAID Controller [8086:2822] (rev 02)

The important things to notice is that both the class ID and the controller VID:PID have changed, from (0106, 8086:2821) to (0104, 8086:2822) respectively.
As it turns out, the 0x0106 class ID is what the Apple AHCI driver uses to find out if a SATA controller is one it should support through AHCI (well, it actually uses 0x01060100 with a 0xffffff00 mask as we will see shortly), so that's the reason why, as soon as our class ID changes to 0x0104, OSX says "Hey, I don't know how to access this type of controller!" and gives up.

That's all very well, but that doesn't tell me how to get my RAID SATA controller recognized

Patience my friend... The key to achieving anything is understanding how it actually works, which we've done, so now is the time to get to the good part.
As you may already be aware, getting hardware recognized on OSX is done through the addition or modification of kexts. A kext, which stands for Kernel Exttension is pretty much the OSX equivalent of a driver or a Linux module. Therefore, to make our RAID controller recognized by the AHCI driver Apple uses, we will need to modify the kexts from our USB installation media to trick the installer into recognizing our non-officially unsupported hardware.

The kext of interest to us is the AppleAHCIPort.kext (makes sense), that resides in /System/Library/Extensions/ (which you will often see abbreviated as S/L/E on hackintosh forums). Most specifically, what we will want to edit is the Info.plist file found in /System/Library/Extensions/AppleAHCIPort.kext/Contents.

If you look at this file you see that it contains a section:

<key>GenericAHCI</key>                                 
<dict>                                                         
        <key>CFBundeIdentifier</key>                     
        <string>com.apple.driver.AppleAHCIPort</string>  
        <key>Chipset Name</key>                          
        <string>AHCI Standard Controller</string>        
        <key>IOClass</key>                               
        <string>AppleAHCI</string>                       
        <key>IOPCIClassMatch</key>                       
        <string>0x01060100&0xffffff00</string>       
        <key>IOProbeScore</key>                          
        <integer>800</integer>                           
        <key>IOProviderClass</key>                       
        <string>IOPCIDevice</string>                     
        <key>Vendor Name</key>                           
        <string>Unknown</string>                         
</dict>

Well, well, well, is that our 0x0106 generic AHCI class right there?

Great, then we just need to change the <string>0x01060100&0xffffff00</string> part to <string>0x01060100&0xffffff00 0x01040000&0xffff0000</string> to add AHCI passthrough support to any RAID controller (if you do have an actual dedicated non SATA RAID controller on your platform, you probably shouldn't use such a blanket approach, but instead duplicate one of the later sections), save the file, reboot, and be done with it, right?

Rebuidling the kext cache

Not so fast! If you just edit and save the Info.plist on the USB key, your RAID controller still will not be detected.
The reason for that is that kexts are executed at the kernel level, so Apple doesn't simply let you load a modified kext like this. Instead, an additional step is needed, which is the rebuilding of what is known as the kext cache. This cache is the Extensions.mkext file located in your /System/Library/ directory (where the Extensions/ directory also resides).

Note that the procedure I am highlighting below can be done from an existing Snow Leopard OS, rather than on the USB key itself, but if you do so, be midnful that there's a whole business going on with regards to permissions and ownership, which, if you mount your USB key as anybody but root (not a problem when using the OSX from the key), may result in an error message such as:

AppleAHCIPort.kext is not authentic; omitting from mkext.
Authentication Failures:
   File owner/permissions are incorrect (must be root:wheel, nonwritable by group/other):
       /Volumes/Mac OS X Install DVD/System/Library/Extensions/AppleAHCIPort.kext/Contents/Info.plist

In our case, we'll run everything from the key, and the default execution level is that of the root user, so it should be fairly simple:

1. Open a terminal window by selecting Utilities→Terminal in the top menu (notice that we haven't had to accept any EULA to do so, so you are free to edit your OSX installation media from the embedded Terminal in any way you like)


2. Remount the USB key as read/write (by default it is mounted read only) by issuing the command:

   mount -u -o rw /

   Note: Make sure you don't close your terminal session after you do that, as Terminal will not launch if the system is already r/w (which is also the reason why we do it manually). You should be able to check that the USB file system is now mounted r/w by issuing mount


3. If you haven't done so already, copy the nano text editor, which you should have copied into the root directory to /usr/bin with the command:
   cp /nano /usr/bin
   Or you can just leave it in root and issue /nano whenever you need to edit a file.


4. Navigate to the Info.plist file we want to edit with cd /System/Library/Extensions/AppleAHCIPort.kext/Contents/ and run nano nano Info.plist


5. Change the <string>0x01060100&0xffffff00</string> line in the <key>GenericAHCI</key> section to <string>0x01060100&0xffffff00 0x01040000&0xffff0000</string>


6. Save the file (Ctrl-X then 'y' to save it)


7. navigate to the /System/Library/ directory with cd /System/Library/. This is the directory that contains the Extensions.mkext file


8. Rebuild the kext cache with:

   kextcache -v 1 -t -l -a i386 -a x86_64 -m Extensions.mkext Extensions

   It should complete without errors (or a benign warning about the JMicronATA.kext) but if there are any issues reported about the AppleAHCIPort.kext, they should be explicitly listed.


9. Close terminal and leave the installer (Mac OS X Installer→Quit Mac OS X Installer) then select Restart. You must restart the installation process completely (i.e. reboot) for our changes to be applied.

With all the above completed, on the second iBoot/USB installer run, you should now see all hard drives recognized, including the ones connected in a SATA connector in RAID mode, with the ability to use them as installation destination. Neat!

Before shouting "victory" though, you should be aware that:

1. When OSX installs, it will extract and install its own unmodified AppleAHCIPort kext (from the Essentials.pkg found in System/Installation/Packages/ directory on the installation media, so what we have done will only work during installation, but the installed OSX will not actually be able to see its disk and we'll have to work around that - bummer!


2. iBoot offers the option to ignore the cache during bootup (press the down key on the OS you want to boot, and then select "Boot Ignore Caches"), so we probably could have gotten away with simply modifying the Info.plist file and used that iBoot option instead of going through this whole cache rebuilding exercise...

Anyway, in the next installement, we'll go through the actual OSX installation process. Stay tuned...