The summary below is helpful for building custom kernels from kernel.org sources. This method of compiling kernels is the traditional method common to all distros; however, an excellent method of cleanly installing the custom kernel with makepkg and pacman is also included.
Alternatively, you can use ABS to build and install your kernel; see: Kernels#Compilation. Using the existing PKGBUILD will automate most of the process and will result in a package. However, some Arch users prefer the traditional way.
- 1 Fetching source
- 2 Build configuration
- 3 Compilation and installation
- 4 Bootloader configuration
- 5 Using the NVIDIA video driver with your custom kernel
- Fetch the kernel source from
ftp.xx.kernel.org/pub/linux/kernel/, where xx is your country key (e.g. 'us', 'uk', 'de', ... - Check  for a complete list of mirrors). If you have no ftp gui, you can use
wget. For this example, we will fetch and compile 3.2.9; you should need to change only the version to get a different kernel.
- It is always a good idea to verify the signature for any downloaded tarball. See kernel.org/signature for how this works and other details.
- Copy the kernel source to your build directory, e.g.:
$ cp linux-3.2.9.tar.bz2 ~/kernelbuild/
- Unpack it and enter the source directory:
$ cd ~/kernelbuild $ tar -xvjf linux-3.2.9.tar.bz2 $ cd linux-3.2.9
Prepare for compilation by running the following command:
This ensures that the kernel tree is absolutely clean. The kernel team recommends that this command be issued prior to each kernel compilation. Do not rely on the source tree being clean after un-tarring.
What about /usr/src/ ?
Using the /usr/src/ directory for kernel compilation as root, along with the creation of the corresponding symlink, is considered poor practice by some kernel hackers. They consider the cleanest method to simply use your home directory. If you subscribe to this point of view, build and configure your kernel as normal user, and install as root, or with makepkg and pacman.
However, this concept has been the target of debate, and other very experienced hackers consider the practice of compiling as root under /usr/src/ to be completely safe, acceptable and even preferable.
Use whichever method you feel more comfortable with.
This is the most crucial step in customizing the kernel to reflect your computer's precise specifications. By setting the configurations in 'menuconfig' properly, your kernel and computer will function most efficiently.
Optional, but strongly recommended for first-timers:
- Copy the .config file from the running kernel, if you want to modify default Arch settings.
$ zcat /proc/config.gz > .config
- Note the output of currently loaded modules with
lsmod. This will be specific to each system.
Configure your kernel
There are two main choices:
$ make menuconfig (Will start with a fresh '.config'. Option dependencies are usually automatically selected.)
Make your changes to the kernel and save your config file. It is a good idea to make a backup copy, since you could be doing this multiple times until you get all the options right. If unsure, only change a few options between compiles. If you cannot boot your newly built kernel, see the list of necessary config items here. Running
$ lspci -k # from liveCD lists names of kernel modules in use. Most importantly, you must maintain
cgroup support. This is necessary for systemd.
Since kernel 2.6.32, localmodconfig is provided to ease kernel configuration. To use this option:
- Boot the distribution kernel, and plug in any devices that you expect to use on the system, which will load the kernel drivers for them. # Go into your kernel source directory, and run
- That option will dig through your system and find the kernel configuration for the running kernel (which is usually at /proc/config.gz, but can sometimes be located in the boot partition, depending on the distribution).
- Then, the script will remove all options for kernel modules that are not currently loaded, stripping down the number of drivers that will be built significantly.
- The resulting configuration file will be written to the .config file, and then you can build the kernel and install it as normal.
If you are compiling a kernel using your current config file, do not forget to rename your kernel version, or you may replace your existing one by mistake.
$ make menuconfig General setup ---> (-ARCH) Local version - append to kernel release '3.n.n-RCn'
Compilation and installation
To compile kernel manually, follow these steps:
$ make (Same as make vmlinux && make modules && make bzImage - see 'make help' for more information on this.)
$ make -jN (N = # of processors + 1) (This utilizes all CPUs at 100%.)
Compilation time will vary from 15 minutes to over an hour. This is largely based on how many options/modules are selected, as well as processor capability.
This needs to be done as root.
# make modules_install
This copies the compiled modules into
/lib/modules/[kernel version + CONFIG_LOCALVERSION]. This way, modules can be kept separate from those used by other kernels on your machine.
Copy kernel to /boot directory
# cp -v arch/x86/boot/bzImage /boot/vmlinuz-YourKernelName
Make initial RAM disk
The initial RAM disk (initrd option in the GRUB menu, or, the file "initramfs-YourKernelName.img") is an initial root file system that is mounted prior to when the real root file system is available. The initrd is bound to the kernel and loaded as part of the kernel boot procedure. The kernel then mounts this initrd as part of the two-stage boot process to load the modules to make the real file systems available and get at the real root file system. The initrd contains a minimal set of directories and executables to achieve this, such as the insmod tool to install kernel modules into the kernel. In the case of desktop or server Linux systems, the initrd is a transient file system. Its lifetime is short, only serving as a bridge to the real root file system. In embedded systems with no mutable storage, the initrd is the permanent root file system.
If you need any modules loaded in order to mount the root filesystem, build a ramdisk (most users need this). The -k parameter accepts the kernel version and appended string you set in menuconfig and is used to locate the corresponding modules directory in '/usr/lib/modules':
# mkinitcpio -k FullKernelName -g /boot/initramfs-YourKernelName.img
Alternatively, if that command doesn't render a bootable kernel, attempt the following:
# mkinitcpio -k FullKernelName -c /etc/mkinitcpio.conf -g /boot/initramfs-YourKernelName.img
You are free to name the /boot files anything you want. However, using the [kernel-major-minor-revision] naming scheme helps to keep order if you: Keep multiple kernels/ Use mkinitcpio often/ Build third-party modules.
If you are using LILO and it cannot communicate with the kernel device-mapper driver, you have to run
modprobe dm-mod first.
The System.map file is not required for booting Linux. It is a type of "phone directory" list of functions in a particular build of a kernel. The System.map contains a list of kernel symbols (i.e function names, variable names etc) and their corresponding addresses. This "symbol-name to address mapping" is used by:
- Some processes like klogd, ksymoops etc
- By OOPS handler when information has to be dumped to the screen during a kernel crash (i.e info like in which function it has crashed).
Copy System.map to /boot and create symlink
# cp System.map /boot/System.map-YourKernelName
After completing all steps above, you should have the following 3 files and 1 soft symlink in your /boot directory along with any other previously existing files:
vmlinuz-YourKernelName (Kernel) initramfs-YourKernelName.img (Ramdisk) System.map-YourKernelName (System Map)
Add an entry for your amazing new kernel in your bootloader's configuration file - see GRUB, LILO, GRUB2 or Syslinux for examples. Note that if you use LILO, the kernel sources include a script to automate the process:
If you use LILO, remember to type
lilo as root at the prompt to update it.
If you use Grub 2, you will probably want to add a menuentry to '/etc/grub.d/40_custom'. The simplest way is to copy an existing menuentry found in your '/boot/grub/grub.cfg' file, modify the entry to include the name of the kernel and image you created, and update grub ('grub-mkconfig -o /boot/grub/grub.cfg').
Grub 2 is also able to automatically locate the new kernel and add an entry for it. You can do this by running:
# grub-mkconfig -o /boot/grub/grub.cfg
Using the NVIDIA video driver with your custom kernel
To use the NVIDIA driver with your new custom kernel, see: How to install nVIDIA driver with custom kernel. You can also install nvidia drivers from AUR.