== How do I compile a kernel? ==

(Also see a working example of building a 3.3.6 Linux kernel in BuildLinux33).

(The following instructions assume we are installing version 5.6.0 of the kernel; replace all instances with the version you are trying to build. These instructions are also x86-specific; other architecture's build procedures may differ.)

 * Download your tarball from the index page at http://kernel.org , which links to the latest versions. For other kernel versions, go to www.kernel.org/pub/linux/kernel/[version] -- where [version] is something like v3.x, v4.x, or v5.x.  Kernel.org has almost-complete kernel archives back to version 0.99 if you're feeling really adventurous. If you know exactly which tarball you want to download, you can also use wget:

{{{
        wget www.kernel.org/pub/linux/kernel/v5.x/linux-5.6.tar.xz
}}}

 * Unpack the tarball in your home directory.  If you're planning to do a lot of compiling and installing kernels (and other good stuff), you may want to read the ''Note on /usr/src'' at the bottom of this page first.

{{{
        tar xJf linux-5.6.0.tar.xz
}}}

 (Replace xJf with xzf if you downloaded the .gz file.)

 * cd into the linux directory. You'll now need to configure the kernel to select the features you want/need. There are several ways to do this..
  a. make config (There are hundreds of questions, so this isn't really a good idea.)
   Command line questions.
  a. make oldconfig
   (Useful only if you kept a .config from a previous kernel build.  With the newest kernels, the .config of the currently-running kernel is used by default if it's available, so you usually won't need this feature.)
  a. make menuconfig or make nconfig
   (ncurses based)
  a. make gconfig
   (GTK+ based X-Windows configuration)
  a. make xconfig
   (QT based X-Windows configuration)

 * Now we can build the kernel (for older kernel like 2.4.x first build the dependencies with "make dep").

{{{
         make
}}}

 * Wait. When it's finished, it will have built both the kernel (bzImage) and the modules (for older kernels like 2.4.x, you need to run "make bzImage ; make modules").
 * Become root to be able to install modules and kernel. Everything before this point can and should be done as a normal user; there is really no need to be root to compile a kernel. It's actually a very bad idea to do everything as root because root is too powerful; one single mistake is enough to ruin your system completely.
 * Install the modules.

{{{
         make modules_install
}}}

 * Install the new kernel..

{{{
         make install 
}}}

If your distribution uses '''lilo''':

 * Edit /etc/lilo.conf, and add these lines...

{{{
         image = /boot/vmlinuz-5.6.0
         label = 5.6.0
}}}

 Also copy your root=/dev/??? line here too.

 * Run /sbin/lilo, reboot, and enjoy.

If your distribution uses '''grub''':

 * Edit /boot/grub/grub.conf or /boot/grub2/grub.cfg:

{{{
          title=Linux 5.6.0
          root (hd0,1) #  or whatever your current root is 
          kernel /boot/vmlinuz-5.6.0 root=/dev/hda1 # or whatever... }}}

 * If you're using Ubuntu, you might need to edit menu.lst or grub.cfg instead of grub.conf  
 * If your menu.lst needs an initrd line, you can generate the necessary info by doing something like


                          update-initramfs -k 5.6.0 -c

             update-initramfs seems to be the replacement for mkinitrd (which is mentioned in the "more indepth tutorial" mentioned below.

 * Most distributions have an installation routine that links a new ''/boot/vmlinuz-[version]'' to simply ''vmlinuz'', so you may want to add a stanza like this to grub.conf/grub.cfg:

{{{
          title=My very latest kernel install
          root (hd0,1) #  or whatever your current root is 
          kernel /boot/vmlinuz root=/dev/hda1 # or whatever... 
}}}

 This will let you boot fresh kernels for testing without constantly editing grub.conf.
''Note: This will work for lilo, too, but you still have to run /sbin/lilo after every install.''

Still not getting it? Try this [[https://linuxreviews.org/Kernel_Rebuild_Guide|more indepth tutorial]]

----
 '''Note on /usr/src'''

If you're just trying out this procedure, do the unpacking and building in your home directory as discussed above.  In a professional environment, though, the source would be stored in /usr/src or /usr/local/src, where compiling would also be done.  To allow this, and at the same time avoid becoming root for the entire procedure, use your favorite GNOME or KDE utilities to create a group "devel" (or "hack" or whatever) and add yourself to that group.  Then change the group owner of /usr/src to the new group and grant write privileges to the group.

That way you can unpack the kernel tarball into /usr/src (or whatever) and configure and build there without doing everything as root.  Of course, you'll still need to ''sudo'' or become root when you install the new kernel and edit the lilo/grub configuration files.

This will help keep the kernel source separate from your resume, diary, and jpegs of your Main Squeeze.

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 [[CategoryFAQ]]
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[[CategoryFAQ]]