Installation: AGX Orin system running Ubuntu or L4T with Linux Sockets

Here are instructions to set up an AGX Orin system running JP6.0 L4T, for use with Linux sockets. While Holoscan sensor bridge applications normally run in a container, these settings are all to be configured in the AGX Orin system directly-not within the container. These instructions are remembered across power cycles and therefore only need to be set up once. Demos and examples in this package assume a sensor bridge device is connected to eth0, which is the RJ45 connector on the AGX Orin.

Install git-lfs.

L4T does not come with git-lfs installed; but some data files in the sensor bridge project use LFS. Fetching the sensor bridge host software from git will require that git-lfs is installed.
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```
            
            sudo apt-get update
sudo apt-get install -y git-lfs
        
```
Linux sockets require a larger network receiver buffer.

Most sensor bridge self-tests use Linux’s loopback interface; if the kernel starts dropping packets due to out-of-buffer space then these tests will fail.
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```
            
            echo 'net.core.rmem_max = 31326208' | sudo tee /etc/sysctl.d/52-hololink-rmem_max.conf
sudo sysctl -p /etc/sysctl.d/52-hololink-rmem_max.conf
        
```
Configure eth0 for a static IP address of 192.168.0.101.

L4T uses NetworkManager to configure interfaces; by default interfaces are configured as DHCP clients. Use the following command to update the IP address to 192.168.0.101. (Here is more information about configuring your system if you cannot use the 192.168.0.0/24 network in this way.)
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```
            
            sudo nmcli con add con-name hololink-eth0 ifname eth0 type ethernet ip4 192.168.0.101/24
sudo nmcli connection up hololink-eth0
        
```
Apply power to the sensor bridge device, ensure that it’s properly connected, then ping 192.168.0.2 to check connectivity.
For the Linux socket based examples, isolating a processor core from Linux kernel is recommended. For high bandwidth applications, like 4k video acquisition, isolation of the network receiver core is required. When an example program runs with processor affinity set to that isolated core, performance is improved and latency is reduced. By default, sensor bridge software runs the time-critical background network receiver process on the third processor core. If that core is isolated from Linux scheduling, no processes will be scheduled on that core without an explicit request from the user, and reliability and performance is greatly improved.

Isolating that core from Linux can be achieved by editing /boot/extlinux/extlinux.conf. Add the setting isolcpus=2 to the end of the line that starts with APPEND. Your file should look like something like this:
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```
            
            TIMEOUT 30
DEFAULT primary

MENU TITLE L4T boot options

LABEL primary
      MENU LABEL primary kernel
      LINUX /boot/Image
      FDT /boot/dtb/kernel_tegra234-p3701-0000-p3737-0000.dtb
      INITRD /boot/initrd
      APPEND ${cbootargs} root=/dev/mmcblk0p1 rw rootwait ...<other-settings>... isolcpus=2
        
```
Sensor bridge applications can run the network receiver process on another core by setting the environment variable HOLOLINK_AFFINITY to the core it should run on. For example, to run on the first processor core,
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```
            
            HOLOLINK_AFFINITY=0 python3 examples/linux_imx274_player.py
        
```
Setting HOLOLINK_AFFINITY to blank will skip any core affinity settings in the sensor bridge code.
Set the AGX Orin power mode to ‘MAXN’ for optimal performance. The setting can be changed via L4T power drop down setting found on the upper left corner of the screen:
Restart the AGX Orin. This allows core isolation and performance settings to take effect. If configuring for ‘MAXN’ performance doesn’t request that you reset the unit, then execute the reboot command manually:
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```
            
            reboot
        
```