Install RT Linux patch for Ubuntu
Here’s for Ubuntu 19.10 and above and I patched Linux 5.4.5 rt kernel patch because Linux 5.3 -- the base of Ubuntu 19.10 -- has no rt kernel patch.
0. Make a working directory
# Make dir and move to working directory
$ mkdir ~/kernel && cd ~/kernel
1. Download kernel and patch
Download kernel and rt patch from https://www.kernel.org/. You can get these below:
(kernel) https://www.kernel.org/pub/linux/kernel/
(rt patch) https://www.kernel.org/pub/linux/kernel/projects/rt/
Note that the version of rt patch and kernel should be same. I used linux-5.4.5.tar.gz and patch-5.4.5-rt3.patch.gz.
If you download these on the ~/kernel, skip below and move on to step 2.
# Move these zip file to ~/kernel
$ cd ~/Download
$ mv linux-5.4.5.tar.gz patch-5.4.5-rt3.patch.gz ~/kernel/.
2. Extract kernel sources and patch rt kernel
# Extract kernel sources
$ cd ~/kernel
$ tar xvzf linux-5.4.5.tar.gz
# Patch rt kernel
$ cd linux-5.4.5
$ gzip -cd ../patch-5.4.5-rt3.patch.gz | patch -p1 --verbose {}
3. Install required packages
For using menuconfig GUI, libncurses-dev
is required. flex
and bison
will be needed when you compile the kernel.
# For using gui
$ sudo apt install libncurses-dev libssl-dev
# For compiling kernel
$ sudo apt install flex bison
4. Configure kernel for RT
$ make menuconfig
and enter the menuconfig GUI.
# Make preemptible kernel setup
General setup ---> [Enter]
Preemption Model (Voluntary Kernel Preemption (Desktop)) [Enter]
Fully Preemptible Kernel (RT) [Enter] #Select
# Select <SAVE> and <EXIT>
# Check .config file is made properly
Note that there’s no Check for stack overflows
option on GUI configuration anymore. You can check it by searching “overflow”. Type / and overflow
on Graphical Menu.
5. Compile the kernel
$ make -j20
$ sudo make modules_install -j20
$ sudo make install -j20
6. Make kernel images lighter
As @mrRo8o7 said earlier, big initrd
image can occur kernel panic. So you can resolve this problem by:
# Strip unneeded symbols of object files
$ cd /lib/modules/5.4.5-rt3 # or your new kernel
$ sudo find . -name *.ko -exec strip --strip-unneeded {} +
# Change the compression format
$ sudo vi /etc/initramfs-tools/initramfs.conf
# Modify COMPRESS=lz4 to COMPRESS=xz (line 53)
COMPRESS=xz
[:wq]
then update initramfs
$ sudo update-initramfs -u
7. Verify and update grub
Verify that directory and update the grub.
# Make sure that initrd.img-5.4.5-rt3, vmlinuz-5.4.5-rt3, and config-5.4.5-rt3 are generated in /boot
$ cd /boot
$ ls
# Update grub
$ sudo update-grub
8. Reboot and verify
$ sudo reboot
# After the reboot
$ uname -a
then you can check your new kernel version
Linux [PROMPT] 5.4.5-rt3 …
Step 0 - Make a working directory
Make a working directory
#Move to working directory
mkdir ~/kernel && cd ~/kernel
Step 1 - Download kernel and patch
Go to https://www.kernel.org/pub/linux/kernel/ and download a desired version of kernel to ~/kernel. Similarly, go to https://www.kernel.org/pub/linux/kernel/projects/rt/ and download the RT patch with same version as the downloaded kernel version. The kernel and patch I used were linux-4.9.115.tar.gz and patch-4.9.155-rt93.patch.gz.
Step 2 - Unzip the kernel
tar -xzvf linux-4.9.115.tar.gz
Step 3 - Patch the kernel
#Move to kernel source directory
cd linux-4.9.115
gzip -cd ../patch-4.9.115-rt93.patch.gz | patch -p1 --verbose
Step 4 - Enable realtime processing This step requires libncurses-dev
sudo apt-get install libncurses-dev libssl-dev
The next command launches a graphical menu in the terminal to generate the config file.
make menuconfig
Go to the location and make the changes accordingly
##Graphical Menu##
Processor type and features ---> [Enter]
Preemption Model (Voluntary Kernel Preemption (Desktop)) [Enter]
Fully Preemptible Kernel (RT) [Enter] #Select
[Esc][Esc]
Kernel hacking --> [Enter]
Memory Debugging [Enter]
Check for stack overflows #Already deselected - do not select
[Esc][Esc]
[Right Arrow][Right Arrow]
<Save> [Enter]
.config
<Okay> [Enter]
<Exit> [Enter]
[Esc][Esc]
[Right Arrow]
<Exit> [Enter]
Step 5 - Compile the kernel
make -j20
sudo make modules_install -j20
sudo make install -j20
Step 6 - Verify and update Verify that initrd.img-4.9.115-rt93, vmlinuz-4.9.115-rt93, and config-4.9.115-rt93 are generated in /boot directory and update the grub.
cd /boot
ls
sudo update-grub
Verify that there is a menuentry containing the text "menuentry 'Ubuntu, with Linux 4.9.115-rt93'" in /boot/grub/grub.cfg
file
To change default kernel in grub, edit the GRUB_DEFAULT
value in /etc/default/grub
to your desired kernel.
NOTE: 0 is the 1st menuentry
7 - Reboot and verify
sudo reboot
Once the system reboots, open the terminal and use uname -a
to check the kernel version, it should look like the following
Linux abhay-home 4.9.115-rt93 #1 SMP PREEMPT RT Mon May 13 03:32:57 EDT 2019 x86_64 x86_64 x86_64 GNU/Linux
Note: "SMP PREEMPT RT" validates that your system is running real time kernel.
After installing the new kernel (like @Abhay Nayak posted), I got into a kernel panic. The problem was that the initrd image was too big. I solved that with:
Step 1 - Strip the kernel modules
cd /lib/modules/<new_kernel>
find . -name *.ko -exec strip --strip-unneeded {} +
Step 2 - Change the initramfs compression
Edit file /etc/initramfs-tools/initramfs.conf:
COMPRESS=xz
Step 3 - Update initramfs
sudo update-initramfs -u
sudo update-grub2