How do I apply a patch to my Linux kernel?

Question

I am trying to compile the iscsi-target software SCST. It wants me to apply a patch to my Linux kernel in order to allow for certain performance gains. The problem is I still new to Linux development. Where do I begin? How do I apply the patch? Do I need to recompile the kernel? Help!

I am running Ubuntu 10.04.3 amd64

Kernel version 2.6.32-28-server

Answer 1

Your Linux distribution usually has its own instructions. Search their website or ask on IRC – or at least tell us the distro; without knowing it, it's impossible to provide a reliable anwer.

• Arch Linux: https://wiki.archlinux.org/index.php/Kernels#Compilation
• CentOS: http://wiki.centos.org/HowTos/Custom_Kernel
• Debian: http://users.wowway.com/~zlinuxman/Kernel.htm, http://debian-handbook.info/browse/stable/sect.kernel-compilation.html, https://www.debian.org/releases/jessie/i386/ch08s06.html.en
• Fedora: https://fedoraproject.org/wiki/Building_a_custom_kernel
• Ubuntu: https://help.ubuntu.com/community/Kernel/Compile

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The generic instructions are:

1. Download the kernel source from Kernel.org. "Stable" is probably the best choice. Extract to a convenient place (I use ~/src/linux).

   • Read the file named README.

2. Once inside the source directory, copy the current kernel's configuration, with:
   zcat /proc/config.gz > .config

   If /proc doesn't have it, look for /boot/config-[version] instead.

3. Apply the patch, with:
   patch -p1 < foo.patch (try -p0 if it gets rejected).

4. Compile the kernel with:
   make silentoldconfig
make

5. Install the modules with:
   sudo make modules_install

6. Install the kernel image .../linux/arch/i386/boot/bzImage to wherever your bootloader wants it. (For example, /boot/vmlinuz-custom.)

7. Build an initramfs for the new kernel, if your distribution uses it, and again make sure the bootloader knows its location. For example, on Arch Linux you would use:
   mkinitcpio -k /boot/vmlinuz-custom -g /boot/initramfs-custom