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KC-01: How do I compile a kernel?

The following instructions apply to every kernel sources (tarball, SRPM, ...) after unpackaging them. If you want to learn how to compile directly (rpmbuild) a kernel SRPM, go to KC-01: How do I compile a SRPM kernel?

A. Unpacking and configuring your kernel:

• Download the kernel sources from www.kernel.org, any kernel.org mirror, or any Mandrake mirror.
  
  
• Unpack the sources in /usr/src/; depending on how the sources are packaged do:
  • *.tgz or *.tar.gz:
    CODE
    /usr/src/# tar xvfz linux-VERSION.tar.gz
    
    /usr/src/# mv linux linux-VERSION && ln -s linux-VERSION linux
    
    
  • *.bz2:
    CODE
    /usr/src/# tar xvfj linux-VERSION.tar.gz
    
    /usr/src/# mv linux linux-VERSION && ln -s linux-VERSION linux
    
    
  • *.src.rpm:
    CODE
    ~# rpm -ivh kernel-VERSION.src.rpm
  Cd into the linux directory.
  
  
  Clean all the rubbish only if you are trying to to compile high patched sources.
  CODE
  make mrproper
  Notice that doing "make mrproper" you'll delete the .config file which stores the default configuration for the particular sources you are compiling, and that you'll have to start from scratch in the following step (kernel configuration). So it will be a good idea to make a backup copy of that file and restore it after the "make mrproper".
  
  
  Edit if you wish the Makefile (<TODO>)
  
  
  Now you'll need to configure the kernel; there are four ways to do this:
  • make xconfig - Is the most intuitive as is X based.
    
  • make menuconfig - Text menus
    
  • make config - Command line. One question after another.
    
  • make oldconfig
    So run your prefered configurator and select the options you need (ie your processor type):
    CODE
    make XXXconfig
  B. Kernel and Modules Compilation

At this point you have your kernel compiled and stored as arch/i386/boot/bzImage.

Notice that if you have already done the "make mrproper" step, you can probably and safely avoid the "make clear" rule (also this step probably can be avoided if you compile the vanilla kernel for the first time).

• If you are compiling a modular kernel (the usual), then there is one step ahead: the modules compilation (At this stage is mandatory that you become root).
  CODE
  make modules modules_install
  Note: you can do a faster module compilation by adding the -jN flag to make (where N is an integer: ie -j5 means "compile 5 things at once")

C. Installing the new Kernel

CODE
cp /usr/src/linux/arch/i386/boot/bzImage /boot/vmlinuz-VERSION
cp /usr/src/linux/System.map /boot/System.map-VERSION
cp /usr/src/linux/.config /boot/config-VERSION
• It is always useful to store a copy of the kernel configuration.
  
  
• In some cases you'll need to create an initrd image in order to be able to load the modules the system needs on boot before the root file system can be mounted:
  CODE
  mkinitrd /boot/initrd-KERNEL-VERSION.img KERNEL-VERSION
  
  
  
• Edit your bootloader and append a new entry for the new kernel (do not replace your old kernel entries until you have tested enough the new kernel). I'll show how a lilo.conf entry should be:
  CODE
  image=/boot/vmlinuz-VERSION
  
      label=new_testing
  
      root=/dev/hda2 # or where ever is your root partition
  
      initrd=/boot/initrd-VERSION.img # in case you need it
  
      append="devfs=mount hdc=ide-scsi" # or which ever flags you need
  
      read-only
  
  
  
• RUN LILO (don't forget):
  CODE
  /sbin/lilo

And that's all!

Further refereneces:
http://www.tldp.org/HOWTO/Kernel-HOWTO.html[/size]