Difference between revisions of "Compiling a kernel"

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This is an example how to compile a Linux kernel. It has been tested for SUSE Linux 10.2 and kernel 2.6.21, but should work same or similar for every combination.
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This is an example how to compile a Linux kernel. It has been tested for SUSE Linux 11.1 and kernel 2.6.27, but should work same or similar for every combination.
  
 
= Check prerequesites =
 
= Check prerequesites =
* Make sure you have a compiler installed
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* Make sure you have a compiler installed - [[open a console]] and issue
  yast -i gcc
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  [[yast]] -i gcc
  
 
= Get the code =
 
= Get the code =
 
* Download the kernel from ftp.kernel.org
 
* Download the kernel from ftp.kernel.org
  wget ftp://ftp.kernel.org/pub/linux/kernel/v2.6/linux-2.6.21.tar.bz2
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  [[wget]] https://kernel.org/pub/linux/kernel/v2.6/linux-2.6.27.tar.bz2
 
* unpack the kernel
 
* unpack the kernel
  bunzip linux-2.6.21.tar.bz2
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  bunzip2 linux-2.6.27.tar.bz2
 
* unpack the kernel for the second time
 
* unpack the kernel for the second time
  tar xvf linux-2.6.21.tar
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  [[tar]] xvf linux-2.6.27.tar
  
 
= Build it =
 
= Build it =
 
* configure the kernel
 
* configure the kernel
  cd linux-2.6.21
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  [[cd]] linux-2.6.27
  make oldconfig
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  [[make]] oldconfig
 
* answer some un-understandable questions
 
* answer some un-understandable questions
The sense of the step ''make oldconfig'' is to tell the kernel its configuration, e.g. which parts should be built as a module, which parts should not be built at all and the name of your special build. The settings are stored in the file ''.config''. E.g. a line <tt>CONFIG_LOCALVERSION="-thorsten"</tt> in .config tells the kernel to call himself 2.6.21-thorsten.
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The sense of the step ''make oldconfig'' is to tell the kernel its configuration, e.g. which parts should be built as a module, which parts should not be built at all and the name of your special build. oldconfig takes over the settings from the running kernel that you can check with <tt>zcat /proc/config.gz</tt> if the switch EXTRACT-IKCONFIG is on. The settings for the new kernel are stored in the file ''.config''. E.g. a line <tt>CONFIG_LOCALVERSION="-thorsten"</tt> in .config would tell kernel 2.6.27 to call himself 2.6.27-thorsten.
* compile the kernel, '''note:''' on a two-CPU VMWare virtual machine with 2.4 GHz, this lasted 19m28.605s
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* compile the kernel,
 
  make -j4
 
  make -j4
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;Note: on a virtual machine with two virtual CPUs @ 2.4 GHz, this lasted 55 minutes.
 
* compile the drivers
 
* compile the drivers
 
  make -j4 modules
 
  make -j4 modules
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  make modules_install
 
  make modules_install
 
* install the kernel
 
* install the kernel
  cp arch/''x86_64''/boot/bzImage /boot/vmlinuz-2.6.21
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  cp arch/''x86_64''/boot/bzImage /boot/vmlinuz-2.6.27
 
This will install the kernel for the ''x86_64'' architecture.
 
This will install the kernel for the ''x86_64'' architecture.
 
* prepare the initial ramdisk
 
* prepare the initial ramdisk
  cp System.map /boot
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  [[cp]] System.map /boot
 
  mkinitrd
 
  mkinitrd
 
This will build an initial ramdisk for all kernels contained in /boot.
 
This will build an initial ramdisk for all kernels contained in /boot.
 
* add an entry to the bootloader. Let's take grub's /boot/grub/menu.lst:
 
* add an entry to the bootloader. Let's take grub's /boot/grub/menu.lst:
  title 2.6.21-selfcompiled
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  title 2.6.27-selfcompiled
 
     root (hd0,0)
 
     root (hd0,0)
     kernel /boot/vmlinuz-2.6.21 root=/dev/sda1
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     kernel /boot/vmlinuz-2.6.27 root=/dev/sda1
     initrd /boot/initrd-2.6.21
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     initrd /boot/initrd-2.6.27
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= See also =
 +
* [[Compiling_kernel_2.6.21]]

Latest revision as of 22:02, 27 March 2020

This is an example how to compile a Linux kernel. It has been tested for SUSE Linux 11.1 and kernel 2.6.27, but should work same or similar for every combination.

Check prerequesites

yast -i gcc

Get the code

  • Download the kernel from ftp.kernel.org
wget https://kernel.org/pub/linux/kernel/v2.6/linux-2.6.27.tar.bz2
  • unpack the kernel
bunzip2 linux-2.6.27.tar.bz2
  • unpack the kernel for the second time
tar xvf linux-2.6.27.tar

Build it

  • configure the kernel
cd linux-2.6.27
make oldconfig
  • answer some un-understandable questions

The sense of the step make oldconfig is to tell the kernel its configuration, e.g. which parts should be built as a module, which parts should not be built at all and the name of your special build. oldconfig takes over the settings from the running kernel that you can check with zcat /proc/config.gz if the switch EXTRACT-IKCONFIG is on. The settings for the new kernel are stored in the file .config. E.g. a line CONFIG_LOCALVERSION="-thorsten" in .config would tell kernel 2.6.27 to call himself 2.6.27-thorsten.

  • compile the kernel,
make -j4
Note
on a virtual machine with two virtual CPUs @ 2.4 GHz, this lasted 55 minutes.
  • compile the drivers
make -j4 modules

Install it

  • install the drivers
make modules_install
  • install the kernel
cp arch/x86_64/boot/bzImage /boot/vmlinuz-2.6.27

This will install the kernel for the x86_64 architecture.

  • prepare the initial ramdisk
cp System.map /boot
mkinitrd

This will build an initial ramdisk for all kernels contained in /boot.

  • add an entry to the bootloader. Let's take grub's /boot/grub/menu.lst:
title 2.6.27-selfcompiled
   root (hd0,0)
   kernel /boot/vmlinuz-2.6.27 root=/dev/sda1
   initrd /boot/initrd-2.6.27

See also