Linux

For upgrading present kernel to linux-next kernel, we need to follow below steps.

1. Check present kernel version:

Check which kernel you have, by running the following command. This should print the version of the kernel that you are using

uname -r

Saving present kernel version in present-version.txt

uname -r > present-version.txt

2. Install required packages:  like "git, make, tar, gcc, bc, patch, dos2unix, wget, xz"

Use below commands based on Linux distro.

zypper --non-interactive install git make tar gcc bc patch dos2unix wget xz

yum install -y git make tar gcc bc patch dos2unix wget xz flex bison openssl-devel elfutils-libelf-devel

apt-get install -y git make tar gcc bc patch dos2unix wget libssl-dev flex bison

3. Download linux-next kernel from git.

git clone git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git

It will download the code into linux-next directory.

cd linux-next/

4. Creating the .config file.

Creating new .config file based on a previous .config file

if you have an existing configuration from an older kernel, copy the old .config file in to linux-next directory as ".config"(recommended way)

cp /boot/config-`uname -r` .config

if old configuration file  not exists, you can create a .config file by running below command

yes "" | make oldconfig

5. Modifications in “.config” file:

a. Enabling HyperV support:

Recent changes to kernel requires setting “CONFIG_HYPERVISOR_GUEST” to enable all guest virtualization drivers. So we need to add CONFIG_HYPERVISOR_GUEST=y to .config file.

CONFIG_HYPERVISOR_GUEST=y

b. Enable Ext4 support:

Ext3 is enabled by default, but in some distros Ext4 is not enable by default.

CONFIG_EXT4_FS=y

6. Configure the kernel options:

This “oldconfig” process will carry over your previous settings, and prompt you if there are new features not covered by your earlier .config file

yes "" | make oldconfig

7. Build the kernel:

Now compile the actual kernel. This can take more than 20 minutes to complete

Based on the processor count, we can run make cmd

make -j`nproc` (running “nproc” processes at a time)

Check make command executed successfully or not.

8. Following changes are needed on OpenSUSE, other distributions may not need this step:

Removing any scsi_id references in /etc/default/grub and /etc/default/grub_installdevice files

and then run "grub2-mkconfig"

grub2-mkconfig

9. Building the kernel modules:

a. Make the modules: Modules are parts of the kernel that are loaded on the fly, as they are needed. They are stored in individual files

make modules

b. Install the modules: This will copy all the modules to a new directory, "/lib/modules/<kernel version>"

make modules_install

10. Installing the kernel:

Now install linux-next kernel using below command.

make install

11. Grub Modification:

Update grub.conf based on grub version, make new kernel as default kernel

For grub V1 files, change default value to 0

default=0

For grub V2 files, run below commands

grub2-mkconfig -o /boot/grub2/grub.cfg

grub2-set-default 0

12. Ensure eth0 is up and running

Sometimes eth0 will not run after reboot, so we need to add below command to either rc.local or after.local based on distro

ifup eth0 > /dev/null

13. Reboot the VM

Reboot the machine, you will be in the new kernel. Check the kernel using "uname -r"

reboot [or] init 6

uname -r

Note: Before reboot check new kernel position in the grub.cfg [or] grub2.cfg with older one and make it as default.

Issues we faced while installing new kernel:

1. Facing errors in crypto/signature/ksign-publickey.c file: For this issue try below procedure.

Run "make menuconfig", Disable "Module signature verification (EXPERIMENTAL)" in "Enable loadable module support" and

Disable "In-kernel signature checker (EXPERIMENTAL)" in "Cryptographic API" save and exit

Now build your kernel with the modified .config file

2. Facing errors Like "lib/locking-selftest.c:1546: error: implicit declaration of function ‘raw_spin_lock_nest_lock’"

You need to replace the raw_spin_lock_nest_lock with spin_lock_nest_lock in ww_test_spin_nest_unlocked function of lib/locking-selftest.c file

3. Facing disk space issues:

For this we need to make sure at least 20GB is available on disk.