Instructions to Download, Compile and Install Linux Kernel.
Step 0: Get the Kernel Source.
• Go to https://www.kernel.org/
• Download the tarball of the latest/stable version into any directory within your home
directory.
• Read more about distinguishing between a stable and development version here:
◦ http://www.makelinux.net/books/lkd2/ch01lev1sec4
• Extract the tarball using
◦ tar -xvfJ linux-x.x.x.tar.xz
• cd into the linux-x.x.x directory thus created.
• Lets call this your build directory.
Step 1: Configure, Build and Install Kernel.
• From the build directory configure the Kernel your are going to build using one of:
◦ make defconfig
◦ make config
◦ make menuconfig
◦ Read more about configuration commands here:
▪ http://www.linux.org/threads/the-linux-kernel-configuring-the-kernel-part-1.4274/
▪ http://www.linuxchix.org/content/courses/kernel_hacking/lesson2)
• Keeping the default options while configuring is fine.
• Now compile the Kernel using:
◦ make
or
◦ make -jx (Where x = 2*no.of cores in your system) to speed up the build.
• Install the Kernel Modules
◦ make modules_install
• Install the new Kernel onto the system using:
◦ make install
• This creates:
◦ kernel image/binary file by the name
▪ vmlinuz-x.x.x*
◦ the initramfs(initial RAM file system) or initrd(initial RAM Disk) by the name
▪ initramfs-x.x.x*
or
▪ initrd.img-x.x.x*
◦ in your /boot directory.
• Here is a list of files of importance created in the /boot directory
◦ vmlinuz-x.x.x* – The actual kernel
◦ System.map-x.x.x* – The symbols exported by the kernel
◦ initrd.img-x.x.x*/initramfs-x.x.x* – temporary root file system used during boot process
◦ config-x.x.x* – The kernel configuration file
• The make install command also executes a update-grub command which will make the
grub (the Grand Unified Boot Loader) aware of the new kernel image available
• and updates /boot/grub/grub.cfg file so that during the next boot the new kernel image
shows up in the GRUB menu.
Step 2: Making your new Kernel the default entry in your GRUB menu.
• In the scenario where you are logging into a remote machine using, for eg., ssh or telnet
you won't be presented with a grub menu. You'll be just logging into an already booted up
machine.
• In order to ensure that you boot into the Kernel that we just built we need to make its entry
the one that is selected by default in the grub menu.
• Open /boot/grub/grub.cfg in any of your favorite text editor.
• Locate the menuentry that has our vmlinuz-x.x.x* image file listed against the linux field
inside the menuentry.
• Our aim is to boot into this menuentry by default.
• For example in the sample grub.cfg, we wish to make the menuentry
◦ 'Ubuntu GNU/Linux, with Xen hypervisor' the default one.
• Note that it is the 3rd main menuentry item in the grub.cfg. Out of all these:
◦ (0) menuentry 'Ubuntu'
◦ (1) submenu 'Advanced options for Ubuntu'
◦ (2) menuentry 'Ubuntu GNU/Linux, with Xen hypervisor'
◦ (3) submenu 'Advanced options for Ubuntu GNU/Linux (with Xen hypervisor)'
• To achieve this open /etc/default/grub in a text editor and update the value of
GRUB_DEFAULT to 2
• That is make the following change:
◦ GRUB_DEFAULT=”2”
• Then issue an update-grub command.
• Another example:
• We wish to make the menuentry
◦ 'Ubuntu, with Linux 3.13.0-32-generic'
• within the submenu item
◦ 'Advanced options for Ubuntu' the default;
• submenu 'Advanced options for Ubuntu' is the 2nd main menuentry item in grub.cfg
• And menuentry 'Ubuntu, with Linux 3.13.0-32-generic' is the 3rd sub-menuentry within
that
◦ (0) menuentry 'Ubuntu'
◦ (1) submenu 'Advanced options for Ubuntu'
▪ (0) menuentry 'Ubuntu, with Linux 3.13.0-39-generic'
▪ (1) menuentry 'Ubuntu, with Linux 3.13.0-39-generic (recovery mode)'
▪ (2) menuentry 'Ubuntu, with Linux 3.13.0-32-generic'
▪ (3) menuentry 'Ubuntu, with Linux 3.13.0-32-generic (recovery mode)'
▪ (4) menuentry 'Ubuntu, with Linux 3.3.1-mortar'
▪ (5) menuentry 'Ubuntu, with Linux 3.3.1-mortar (recovery mode)'
◦ (2) menuentry 'Ubuntu GNU/Linux, with Xen hypervisor'
◦ (3) submenu 'Advanced options for Ubuntu GNU/Linux (with Xen hypervisor)'
• In order to boot into this we need to make the following change in /etc/defaults/grub
◦ GRUB_DEFAULT=”1>2”
• Follow it up by an update-grub command.
• For additional info look up
https://help.ubuntu.com/community/Grub2/Submenus#Setting_a_Submenu_entry_as_the_d
efault
• Once you've made all the changes reboot.
• Note that you won't be able to log into the remote system until it reboots.
• Once you've logged into the re-booted system check whether you've booted into the latest
compiled kernel with
◦ uname -r command.
