How do you replace a kernel

[badbonez]

Hi all, I'm pretty new to this but looking forward to the 10.5.2 release. Someone wrote in another thread that you can backup your current kernel in case the new update doesn't work. My question is, how do you do that? What exactly is the kernel? Is it a single file or a group of files? I've searched this forum and searched the google, but nothing clear comes up.

 

Many thanks in advance!

[Wrenbird]

theres a file named mach_kernel in your root directory. that's the kernel. Just copy it to your desktop before updating (you may need to move/replace the kernel in another OS or terminal) and put it back after it.

[badbonez]

Thanks Wrenbird...as you can guess, I'm still new to this. Can anyone tell me what the terminal commands would be? I've tried:

sudo cp -R \Volumes\Leopard\mach_kernel \Volumes\Desktop

but apparently that's not the right syntax.

 

Thanks again.

[mrogers]

LOL no, you don't use backslashes in OS X for file paths! Or *any* OS except for Windows, for that matter.

 

It should just be (assuming /Volumes/Leopard is your mounted OS X installation)

 

sudo cp -R /Volumes/Leopard/mach_kernel /Volumes/Leopard/users/yourusername/Desktop/

 

Don't forget the trailing slash at the end of whatever path you choose to copy it to; if I left off the last "/" at the end of the above command, for example, it would attempt to copy the mach_kernel file and then rename it "Desktop". Having the trailing slash "/" means "put the file inside the Desktop folder".

[badbonez]

LOL no, you don't use backslashes in OS X for file paths! Or *any* OS except for Windows, for that matter.

 

It should just be (assuming /Volumes/Leopard is your mounted OS X installation)

 

sudo cp -R /Volumes/Leopard/mach_kernel /Volumes/Leopard/users/yourusername/Desktop/

 

Don't forget the trailing slash at the end of whatever path you choose to copy it to; if I left off the last "/" at the end of the above command, for example, it would attempt to copy the mach_kernel file and then rename it "Desktop". Having the trailing slash "/" means "put the file inside the Desktop folder".

 

Thanks for that tip on the slashes, I get them confused (still new)

 

EDIT: GOT IT (once I had the right volume name) Big thanks!

 

Can anyone tell me what the -R mean? I found a website with the terminal commands but it doesn't list the switches.

 

Thanks again!

[trash23]

Can anyone tell me what the -R mean? I found a website with the terminal commands but it doesn't list the switches.

 

Type this in your Terminal.app, it will show you the manual of the cp command:

 man cp

[Envying]

after you get a new kernel, just rename it to mach1052 or sth else, copy it to your root, boot your system and type in mach1052....

[socal swimmer]

I'm pretty sure you don't need to use "cp -R" because mach_kernel is a file not a directory, so you don't need to copy recursively.

 

Also, the way I (and most, I think) have always done it is to do

 

sudo cp /mach_kernel /mach_kernel.bak <press enter>

 

this makes a copy of it called mach_kernel.bak. If you have problems with the new one, then just copy the backed up one to the main one. This is much easier to type in .

 

 

 

 

another way:

 

if you wish to boot with another kernel just once, for testing, you can do this:

 

go into boot options (at darwin boot) and type:

 

kernel=/path/to/test/kernel/mach_kernel

 

I think ... I haven't tried but it makes sense and in com.apple.Boot.plist there is a place where the kernel is named.

 

 

 

sorry if i'm rambling...

[Korrupted]

You don't have to use kernel=. Just type your kernel name on the boot: line.

Example:

 

/mach_kernel.old -v -f

 

This'll boot your alternative kernel, verbose mode, and force check kexts.