How to update the semthex Mac OS X kernel (10.4.8)

Those familiar with the OSX86project might know that semthex has been releasing new kernel updates on a fairly regular basis. If you barely muddled your way through the initial install, well… updating the the kernel isn’t exactly a piece of cake. Nevertheless, here are some instructions that might help you…

Oh and before we continue, I’m going to assume that you’re currently able to run OS X, and are simply looking to update the kernel.

1) Download the latest kernel. Currently, the easiest way is to grab the link from the #kernel channel on . The link (to a .rar file) is usually mentioned in the topic. For example, at the time of this writing, it was a link to li-rc12.rar . If you’re not familiar with IRC, well, you might be in for a small learning experience. If you need an IRC client for Windows, do a google search for mIRC. If you need one for the MacOS, google for Colloquy. mIRC is shareware, Colloquy is open source.

2) If you’re not booted into OS X, do it now. Follow the link to that .rar file and download it. Once you have the .rar, open it. Stuffit Expander works fine for this. A file called “mach_kernel” should be extracted to the desktop. It *might* be invisible. If it is, you might want to open a terminal window to make sure it’s there.

3) Assuming the “mach_kernel” file is there on the desktop, reboot the computer. After the BIOS screen goes by, hit the F8 key. It should bring up a “boot menu” of sorts. Type in:
and press enter. This should boot into “single-user mode”. You won’t have a GUI. You’ll be left at a command prompt of sorts.

4) Type the following:
mount -uw /
mv /mach_kernel /mach_kernel.old
cp /Users/yourusername/Desktop/mach_kernel /mach_kernel
chown root:wheel mach_kernel
chmod 644 mach_kernel

Replace “yourusername” with your user name. Most everything is case-sensitive (including the username) so keep that in mind. These instructions were taken from a post in the osx86forums, but I’ve followed them with success.

If something goes wrong (like you type in the wrong username and can’t figure out what it is), before you type reboot, type:
mv /mach_kernel.old /mach_kernel
I’m not a unix wiz, but as far as I can tell, that should restore the original mach_kernel file.

5) Assuming everything goes according to plan (reboots successfully with the new kernel), remember to erase the mach_kernel file from the desktop before downloading a new one.