depot/pkgs/os-specific/linux/kernel

How to add a new (major) version of the Linux kernel to Nixpkgs:

1. Copy the old Nix expression (e.g., linux-2.6.21.nix) to the new one (e.g., linux-2.6.22.nix) and update it.

2. Add the new kernel to the kernels attribute set in linux-kernels.nix (e.g., create an attribute kernel_2_6_22).

3. Update the kernel configuration:

   1. While in the Nixpkgs repository, enter the development shell for that kernel:

      $ nix-shell -A linuxKernel.kernels.linux_2_6_22
      

   2. Unpack the kernel:

      [nix-shell]$ pushd $(mktemp -d)
      [nix-shell]$ unpackPhase
      

   3. For each supported platform (i686, x86_64, uml) do the following:

      1. Make a copy from the old config (e.g., config-2.6.21-i686-smp) to the new one (e.g., config-2.6.22-i686-smp).

      2. Copy the config file for this platform (e.g., config-2.6.22-i686-smp) to .config in the unpacked kernel source tree.

      3. Run make oldconfig ARCH={i386,x86_64,um} and answer all questions. (For the uml configuration, also add SHELL=bash.) Make sure to keep the configuration consistent between platforms (i.e., don’t enable some feature on i686 and disable it on x86_64).

      4. If needed, you can also run make menuconfig:

         $ nix-shell -p ncurses pkg-config
         $ make menuconfig ARCH=arch
         

      5. Copy .config over the new config file (e.g., config-2.6.22-i686-smp).

4. Test building the kernel:

nix-build -A linuxKernel.kernels.kernel_2_6_22

If it compiles, ship it! For extra credit, try booting NixOS with it.

5. It may be that the new kernel requires updating the external kernel modules and kernel-dependent packages listed in the linuxPackagesFor function in linux-kernels.nix (such as the NVIDIA drivers, AUFS, etc.). If the updated packages aren’t backwards compatible with older kernels, you may need to keep the older versions around.