@orat

If you are still looking to install kernel with PREEMPT-RT compatibility w/ Nvidia drivers, try the following method. We were successful in doing so, although we had to use a much older kernel (5.4.78). Although FYI we still face the ‘Could not get fresh data package from robot’ error.

Setting up Linux Kernel with Real-Time Capabilities

Building and Installing Real-Time Kernel

## Set up source lists and install required dependencies
echo "deb-src http://archive.ubuntu.com/ubuntu focal main" | sudo tee -a /etc/apt/sources.list.d/focal.list
sudo apt-get update
sudo apt-get build-dep linux
sudo apt-get install libncurses-dev flex bison openssl libssl-dev dkms libelf-dev libudev-dev libpci-dev libiberty-dev autoconf fakeroot dwarves

## Create installation and build directories. Can be deleted after the kernel is installed and functional
mkdir ~/kernel && cd ~/kernel

## Installing and patching Linux Ubuntu 5.4 kernel with real-time patch
## Instructions copied from (https://docs.ros.org/en/foxy/Tutorials/Building-Realtime-rt_preempt-kernel-for-ROS-2.html)
wget https://mirrors.edge.kernel.org/pub/linux/kernel/v5.x/linux-5.4.78.tar.gz
tar -xzf linux-5.4.78.tar.gz
wget http://cdn.kernel.org/pub/linux/kernel/projects/rt/5.4/older/patch-5.4.78-rt44.patch.gz
gunzip patch-5.4.78-rt44.patch.gz
cd linux-5.4.78/
patch -p1 < ../patch-5.4.78-rt44.patch

## Editing configs for build
cp /boot/config${MOST RECENT KERNEL} .config
yes '' | make oldconfig
make menuconfig

In the terminal GUI, do:

# Enable CONFIG_PREEMPT_RT
 -> General Setup
  -> Preemption Model (Fully Preemptible Kernel (Real-Time))
   (X) Fully Preemptible Kernel (Real-Time)

# Enable CONFIG_HIGH_RES_TIMERS
 -> General setup
  -> Timers subsystem
   [*] High Resolution Timer Support

# Enable CONFIG_NO_HZ_FULL
 -> General setup
  -> Timers subsystem
   -> Timer tick handling (Full dynticks system (tickless))
    (X) Full dynticks system (tickless)

# Set CONFIG_HZ_1000 (note: this is no longer in the General Setup menu, go back twice)
 -> Processor type and features
  -> Timer frequency (1000 HZ)
   (X) 1000 HZ

# Set CPU_FREQ_DEFAULT_GOV_PERFORMANCE [=y]
 ->  Power management and ACPI options
  -> CPU Frequency scaling
   -> CPU Frequency scaling (CPU_FREQ [=y])
    -> Default CPUFreq governor (<choice> [=y])
     (X) performance

in .config remove the KEYS

CONFIG_SYSTEM_TRUSTED_KEYS="debian/canonical-certs.pem" > CONFIG_SYSTEM_TRUSTED_KEYS=""

run the make:

## Making .deb packages will take a lot of time (~10-30 mins)
make -j `nproc` deb-pkg

## Check build there should be 4 .deb files
ls ../*deb

## Install .deb. This will also take some time
sudo dpkg -i ../*.deb

Preparing Real-Time Kernel for UR Integration

sudo groupadd realtime
sudo usermod -aG realtime $(whoami)

Then, make sure /etc/security/limits.conf contains. If it does not, then open it as superuser and copy in the below lines into the file:

@realtime soft rtprio 99
@realtime soft priority 99
@realtime soft memlock 102400
@realtime hard rtprio 99
@realtime hard priority 99
@realtime hard memlock 102400

Check for RT capabilities

## Update grup and reboot
sudo update-grub
sudo reboot

## Once returned to the rt kernel, check if PREEMPT-RT is functional
uname -v | cut -d" " -f1-4
## Outpu should read >> #1 SMP PREEMPT_RT

Installing Real-Time Compatible Graphic Drivers

Download .run file for a compatible NVIDIA Driver (version 455) using following website:

https://www.nvidia.com/Download/driverResults.aspx/166177/en-us

Create/Edit following file:

sudo nano /etc/modprobe.d/blacklist-nouveau.conf

If the lines do not already exist, add the following lines:

blacklist nouveau
options nouveau modeset=0

Update kernel initramfs

sudo update-initramfs -u
sudo reboot

Upon reboot, login to the real-time kernel through Recovery Mode and access kernel though root. Then, navigate to the location where the .run file is downloaded and run the following command:

sudo IGNORE_PREEMPT_RT_PRESENCE=1 bash NVIDIA-Linux-x86_64-455.38.run

Move through installation with default option (i.e. select Yes for everything). Then exit root and boot normally.

Once this is done, check the installation of NVIDIA driver with command:

nvidia-smi

It should show something like:

+-----------------------------------------------------------------------------+
| NVIDIA-SMI 455.38       Driver Version: 455.38       CUDA Version: 11.1     |
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|                               |                      |               MIG M. |
|===============================+======================+======================|
|   0  GeForce GTX 105...  Off  | 00000000:01:00.0  On |                  N/A |
| 30%   35C    P0    N/A /  75W |    215MiB /  4031MiB |      1%      Default |
|                               |                      |                  N/A |
+-------------------------------+----------------------+----------------------+