This blog post provides a step-by-step tutorial on compiling and booting from Linux Kernel 6.x. We will use a VM environment for safety. This blog post is ideal for developers and curious learners. I assume reader has basic understanding of Linux OS. Setting up a playground I am using Oracle VirtualBox v7.0 on the Ubuntu (v24.04) x86_64 Host. Download Ubuntu 20.04 iso. In Virtualbox, create a new VM machine by providing the iso image. Select Skip Unattended Installation option. This is optional, but I prefer to choose this to observe what’s going on. Minimum resources to allocate are - 2 vCPUs 2 GB RAM 100 GB o Hard Disk space. Once finished, Ubuntu OS will boot and provide option to install it. During installation, choose minimal installation option and do not install extra third party softwares. This is because we simply don’t need these things atm. Post starting the VM, check the kernel version. I see following at my end. uname -r 5.15.0-126-generic uname -a Linux kernel0 5.15.0-126-generic #136~20.04.1-Ubuntu SMP Thu Nov 14 16:38:05 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux Do update and upgrade sudo apt update sudo apt upgrade Reboot the VM once above is completed. Install SSH Server and enable it sudo apt install -y openssh-server systemctl enable --now ssh Now install few useful tools wget -4 https://raw.githubusercontent.com/simplyatul/vagrant-vms/main/tools-0-install.sh chmod +x tools-0-install.sh sudo ./tools-0-install.sh Then install the packages required to build the kernel wget -4 https://raw.githubusercontent.com/simplyatul/vagrant-vms/refs/heads/main/tools-0-kernel-dev.sh chmod +x tools-0-kernel-dev.sh sudo ./tools-0-kernel-dev.sh Kernel code config Let us now checkout stable kernel version git clone -4 --depth=1 --branch v6.8.12 git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git cd linux-stable To build the kernel, .config file is required. This file contains kernel configurations. I have used my host’s config file for this # Copy /boot/config-6.8.0-48-generic from my host PC to VM's /tmp directory cp /tmp/config-6.8.0-48-generic .config Now do menuconfig make menuconfig # Make following changes # General Setup -> Kernel .config support => Make it * # General Setup -> Kernel .config support -> Enable access to .config through /proc/config.gz => Select it # General Setup -> Local version - append to kernel release => Enter -at-bl0 (Or put some identifier of your choice) # Exit and Save Disable following options scripts/config --disable SYSTEM_TRUSTED_KEYS scripts/config --disable SYSTEM_REVOCATION_KEYS # Note => while "make" command is running, if any certificate related question arises, then simply hit Enter. Kernel build Gr8, all config is done. Time to build the kernel time make -j6 2>&1 | tee build-0.log If all goes well, you should see a statement like below at the end Kernel: arch/x86/boot/bzImage is ready (#2) Check the vmlinux file has created ls -lh vmlinux -rwxrwxr-x 1 kernel0 kernel0 469M Dec 17 16:57 vmlinux Kernel install On Ubuntu, you can run following to install newly built kernel sudo make -d modules_install install 2>&1 | tee make-install-0.log Above command installs the kernel to /boot/, installs modules to /lib/modules/X.Y.Z/ (where X.Y.Z is 6.8.12-at-bld0 in our case), and updates file /boot/grub/grub.conf. Now update following configs in /etc/default/grub file GRUB_TIMEOUT_STYLE=hidden GRUB_TIMEOUT=0 to #GRUB_TIMEOUT_STYLE=hidden GRUB_TIMEOUT=15 This ensures you see boot option for 15 sec before it automatically boots. At end, update the grub sudo update-grub2 Post reboot, you should see newly installed kernel is in action uname -r 6.8.12-at-bld0 uname -a Linux kernel0 6.8.12-at-bld0 #2 SMP PREEMPT_DYNAMIC Tue Dec 17 16:56:45 IST 2024 x86_64 x86_64 x86_64 GNU/Linux # Note the version number 6.8.12-at-bld0 has suffix "-at-bld0" which we had entered during kernel code config step above. Note the version number 6.8.12-at-bld0 has suffix -at-bld0 which we had entered during kernel code config step above. Every time you build the new kernel, ensure to update this suffix. Notes I used -4 option in few of the commands above. This instruct to use IPv4. This is because I was facing few issues with IPv6. References https://kernelnewbies.org/KernelBuild Book: Linux Kernel Programming (Second Edition) By Kaiwan N. Billimoria Kernel Workspace Setup This blog post provides a step-by-step tutorial on compiling and booting from Linux Kernel 6.x. We will use a VM environment for safety. This blog post is ideal for developers and curious learners. I assume reader has basic understanding of Linux OS. Setting up a playground I am using Oracle VirtualBox v7.0 on the Ubuntu (v24.04) x86_64 Host. Download Ubuntu 20.04 iso . In Virtualbox, create a new VM machine by providing the iso image. Select Skip Unattended Installation option. This is optional, but I prefer to choose this to observe what’s going on. Oracle VirtualBox v7.0 Ubuntu 20.04 iso Skip Unattended Installation Minimum resources to allocate are - 2 vCPUs 2 GB RAM 100 GB o Hard Disk space. 2 vCPUs 2 GB RAM 100 GB o Hard Disk space. Once finished, Ubuntu OS will boot and provide option to install it. During installation, choose minimal installation option and do not install extra third party softwares . This is because we simply don’t need these things atm. minimal installation extra third party softwares Post starting the VM, check the kernel version. I see following at my end. uname -r 5.15.0-126-generic uname -a Linux kernel0 5.15.0-126-generic #136~20.04.1-Ubuntu SMP Thu Nov 14 16:38:05 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux uname -r 5.15.0-126-generic uname -a Linux kernel0 5.15.0-126-generic #136~20.04.1-Ubuntu SMP Thu Nov 14 16:38:05 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux Do update and upgrade sudo apt update sudo apt upgrade sudo apt update sudo apt upgrade Reboot the VM once above is completed. Install SSH Server and enable it sudo apt install -y openssh-server systemctl enable --now ssh sudo apt install -y openssh-server systemctl enable --now ssh Now install few useful tools wget -4 https://raw.githubusercontent.com/simplyatul/vagrant-vms/main/tools-0-install.sh chmod +x tools-0-install.sh sudo ./tools-0-install.sh wget -4 https://raw.githubusercontent.com/simplyatul/vagrant-vms/main/tools-0-install.sh chmod +x tools-0-install.sh sudo ./tools-0-install.sh Then install the packages required to build the kernel wget -4 https://raw.githubusercontent.com/simplyatul/vagrant-vms/refs/heads/main/tools-0-kernel-dev.sh chmod +x tools-0-kernel-dev.sh sudo ./tools-0-kernel-dev.sh wget -4 https://raw.githubusercontent.com/simplyatul/vagrant-vms/refs/heads/main/tools-0-kernel-dev.sh chmod +x tools-0-kernel-dev.sh sudo ./tools-0-kernel-dev.sh Kernel code config Let us now checkout stable kernel version git clone -4 --depth=1 --branch v6.8.12 git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git cd linux-stable git clone -4 --depth=1 --branch v6.8.12 git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git cd linux-stable To build the kernel, .config file is required. This file contains kernel configurations. I have used my host’s config file for this .config # Copy /boot/config-6.8.0-48-generic from my host PC to VM's /tmp directory cp /tmp/config-6.8.0-48-generic .config # Copy /boot/config-6.8.0-48-generic from my host PC to VM's /tmp directory cp /tmp/config-6.8.0-48-generic .config Now do menuconfig menuconfig make menuconfig # Make following changes # General Setup -> Kernel .config support => Make it * # General Setup -> Kernel .config support -> Enable access to .config through /proc/config.gz => Select it # General Setup -> Local version - append to kernel release => Enter -at-bl0 (Or put some identifier of your choice) # Exit and Save make menuconfig # Make following changes # General Setup -> Kernel .config support => Make it * # General Setup -> Kernel .config support -> Enable access to .config through /proc/config.gz => Select it # General Setup -> Local version - append to kernel release => Enter -at-bl0 (Or put some identifier of your choice) # Exit and Save Disable following options scripts/config --disable SYSTEM_TRUSTED_KEYS scripts/config --disable SYSTEM_REVOCATION_KEYS # Note => while "make" command is running, if any certificate related question arises, then simply hit Enter. scripts/config --disable SYSTEM_TRUSTED_KEYS scripts/config --disable SYSTEM_REVOCATION_KEYS # Note => while "make" command is running, if any certificate related question arises, then simply hit Enter. Kernel build Gr8, all config is done. Time to build the kernel time make -j6 2>&1 | tee build-0.log time make -j6 2>&1 | tee build-0.log If all goes well, you should see a statement like below at the end Kernel: arch/x86/boot/bzImage is ready (#2) Kernel: arch/x86/boot/bzImage is ready (#2) Check the vmlinux file has created ls -lh vmlinux -rwxrwxr-x 1 kernel0 kernel0 469M Dec 17 16:57 vmlinux ls -lh vmlinux -rwxrwxr-x 1 kernel0 kernel0 469M Dec 17 16:57 vmlinux Kernel install On Ubuntu, you can run following to install newly built kernel sudo make -d modules_install install 2>&1 | tee make-install-0.log sudo make -d modules_install install 2>&1 | tee make-install-0.log Above command installs the kernel to /boot/ , installs modules to /lib/modules/X.Y.Z/ (where X.Y.Z is 6.8.12-at-bld0 in our case), and updates file /boot/grub/grub.conf . /boot/ /lib/modules/X.Y.Z/ /boot/grub/grub.conf Now update following configs in /etc/default/grub file /etc/default/grub GRUB_TIMEOUT_STYLE=hidden GRUB_TIMEOUT=0 GRUB_TIMEOUT_STYLE=hidden GRUB_TIMEOUT=0 to #GRUB_TIMEOUT_STYLE=hidden GRUB_TIMEOUT=15 #GRUB_TIMEOUT_STYLE=hidden GRUB_TIMEOUT=15 This ensures you see boot option for 15 sec before it automatically boots. At end, update the grub sudo update-grub2 sudo update-grub2 Post reboot, you should see newly installed kernel is in action uname -r 6.8.12-at-bld0 uname -a Linux kernel0 6.8.12-at-bld0 #2 SMP PREEMPT_DYNAMIC Tue Dec 17 16:56:45 IST 2024 x86_64 x86_64 x86_64 GNU/Linux # Note the version number 6.8.12-at-bld0 has suffix "-at-bld0" which we had entered during kernel code config step above. uname -r 6.8.12-at-bld0 uname -a Linux kernel0 6.8.12-at-bld0 #2 SMP PREEMPT_DYNAMIC Tue Dec 17 16:56:45 IST 2024 x86_64 x86_64 x86_64 GNU/Linux # Note the version number 6.8.12-at-bld0 has suffix "-at-bld0" which we had entered during kernel code config step above. Note the version number 6.8.12-at-bld0 has suffix -at-bld0 which we had entered during kernel code config step above. Every time you build the new kernel, ensure to update this suffix. 6.8.12-at-bld0 -at-bld0 Notes I used -4 option in few of the commands above. This instruct to use IPv4. This is because I was facing few issues with IPv6. I used -4 option in few of the commands above. This instruct to use IPv4. This is because I was facing few issues with IPv6. -4 References https://kernelnewbies.org/KernelBuild Book: Linux Kernel Programming (Second Edition) By Kaiwan N. Billimoria Kernel Workspace Setup https://kernelnewbies.org/KernelBuild Book: Linux Kernel Programming (Second Edition) By Kaiwan N. Billimoria Linux Kernel Programming Kernel Workspace Setup Kernel Workspace Setup
