Following are the few things you should have installed on your machine, before starting to build your kernel.
$ sudo apt update
$ sudo apt install libelf-dev
$ sudo apt install libssl-dev
$ sudo apt install libncurses-dev
$ sudo apt install flex
$ sudo apt install bison
$ sudo apt install pkg-config
$ sudo apt install gcc
Welcome! This is the documentation of the steps I followed to successfully compile a kernel. Before actually diving into the kernel install, check the version which you are originally running using the following command.
$ uname -r
4.4.0-116-generic
The command shows the current version of the kernel, which on my system
is 4.4.0-116-generic. At the time of
writing the documentation, the latest version is 4.16.13. The latest
version for the kernel can be checked here
Once you have decided onto the version of the kernel you want to build, next step is to download the kernel. I used wget for the same, but there are other ways as well.
Type the following command in your terminal:
$ wget https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.16.13.tar.xz
The following command will download a tar.xz archives for you. To extract the files, use the following command:
$ tar -xf linux-4.16.13.tar.xz
The command will extract the contents of the tar file.
NOTE: You will have to write your own version instead of 4.16.13.
NOTE: To install the net-next, I used git clone instead of
getting the kernel folder. The command for same is given below. Also
note that you are not required to go through the extract the archive
steps.
git clone https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git
This might be a huge file and if you are working with the kernel for
experimental purposes and do not intend to work as a Linux Kernel
Developer, you might want to run it with the --depth=1 option.
git clone --depth=1 https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git
The --depth option is used with git clone to create a shallow clone
with its history truncated.
NOTE: Before proceeding make sure you have enough space in your disk to complete the kernel build.
To know the space in various partitions, do
$ df -h
You will get results like these:
Filesystem Size Used Avail Use% Mounted on
udev 32G 0 32G 0% /dev
tmpfs 6.3G 9.0M 6.3G 1% /run
/dev/nvme0n1p1 16G 3.2G 12G 22% /
tmpfs 32G 0 32G 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 32G 0 32G 0% /sys/fs/cgroup
ops.utah.cloudlab.us:/proj/cloudlab-PG0 100G 24G 77G 24% /proj/cloudlab-PG0
ops.utah.cloudlab.us:/share 97G 10G 80G 12% /share
tmpfs 6.3G 0 6.3G 0% /run/user/20001
On an average the kernel build requires much more space than its actual
size. The size of the kernel can be found out by du -ch.
$ cd linux-4.16.13
$ du -ch
919M
The command du will tell you about the size of the folder in a format
depending on the flags specified. The h flag will produce the result
in human-readable format (e.g. 200K, 960M). The c flag gives the
grand-total of all the contents of the folder. For more info on the
options available to the command, do man du.
In my case, it was 919M. Also note that the kernel size will vary based on the drivers and configuration you choose for your kernel, the command for which is explained later. It is recommended to make proper space (at least 4GB) in your disk before building the kernel. The instructions for making extra space in your system can be found here
The steps from now focus on building the kernel.
$ cd /linux-4.16.13
The next task in hand is to configure the kernel to tell it about the modules to be included.
$ sudo make menuconfig
The command will open a TUI (Text-Based UI) for the configuration, with directions on the top to select/de-select. The configuration I chose for TCP_BBR experiment is described below.
Networking Support --> Networking Options --> TCP: Advanced Congestion Control --> BBR TCP
NOTE: You could also make TCP as the default congestion control but I decided it to do it manually later.
After you are done with choosing your
configuration, save the configuration and exit.
This generates a .config file.
NOTE: It is recommended to make a copy of your existing kernel before making any changes.
Now we move on to compiling the kernel and the kernel modules. The
command for doing the same is make. Before proceeding I checked the
number of processors available to the current process to speed up the
process by using the linux command nproc.
$ nproc
16
$ sudo make -j 16
Now compile the kernel modules using the following command:
$ sudo make modules_install -j 16
Now the .config file and the kernel needs to be copied to the
/bootfolder along with the generation of the system.map file.
$ sudo make install -j 16
We have compiled the kernel successfully. Now to let the system use the new kernel when it boots up next, we need to update the grub.
$ sudo update-initramfs -c -k 4.16.13
$ sudo update-grub
NOTE: While building the net-next, the version is 4.17.0-rc+. Make
sure to use the right kernel version which can also be known from the
last command used i.e sudo make install, the initial output for which is
given here.
sh ./arch/x86/boot/install.sh 4.17.0-rc7+ arch/x86/boot/bzImage \
System.map "/boot"
You can check the version here. [NOTE ENDS HERE]
NOTE:It may actually not be required to run the last two commands i.e
sudo update-grub and sudo update-initramfs <version-num>. Look for
the following lines in the output of sudo make install -j $(nproc).
update-initramfs: Generating /boot/initrd.img-4.17.0+
run-parts: executing /etc/kernel/postinst.d/zz-update-grub 4.17.0+ /boot/vmlinuz-4.17.0+
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.17.0+
Found initrd image: /boot/initrd.img-4.17.0+
Found linux image: /boot/vmlinuz-4.17.0+.old
Found initrd image: /boot/initrd.img-4.17.0+
Found linux image: /boot/vmlinuz-4.4.0-116-generic
Found initrd image: /boot/initrd.img-4.4.0-116-generic
Found memtest86+ image: /boot/memtest86+.elf
Found memtest86+ image: /boot/memtest86+.bin
done
This denotes that the above mentioned two commands have already been executed and you do not need to run them again. Skip to rebooting the system.
After the above commands run successfully, reboot the system to start working with the new kernel.
You can always verify the kernel with uname -r.
$ uname -r
4.16.13
This shows that the kernel has been successfully compiled and running.
Cheers!!
Credits and Sources