🧠 Introduction to Linux Basics on Jetson¶
Author: Dr. Kaikai Liu, Ph.D.
Position: Associate Professor, Computer Engineering
Institution: San Jose State University
Contact: kaikai.liu@sjsu.edu
This document introduces the fundamentals of the Linux operating system with a focus on practical usage for students working on NVIDIA Jetson devices like the Orin Nano. You'll also learn about NVIDIA's custom Linux version: L4T.
📚 What is Linux?¶
Linux is an open-source operating system that powers everything from phones to servers. Jetson uses a specialized version of Ubuntu Linux.
Key Characteristics:
- Open-source and customizable
- Multi-user, multi-tasking environment
- Command-line and graphical interfaces
- High performance and low resource usage
🏗️ Linux System Architecture¶
Linux architecture is typically divided into:
1. Kernel¶
- Core of the OS that interfaces with hardware
- Manages memory, processes, file systems, device drivers
2. Shell¶
- Interface that accepts user commands (CLI)
- Common shells:
bash,zsh,sh
3. File System Hierarchy¶
/: Root of the filesystem/bin,/sbin: Essential binaries/usr: Secondary hierarchy for user-installed software/etc: Configuration files/home: Personal user directories/dev,/proc,/sys: Virtual files for devices and kernel state
4. User Space and Daemons¶
- System and user-level applications
- Daemons provide background services (e.g.,
systemd,networkd)
🧩 What is Jetson L4T?¶
L4T (Linux for Tegra) is NVIDIA’s embedded Linux distribution tailored for Jetson SoCs (System-on-Chip). It extends standard Ubuntu with:
📦 Components:¶
- Ubuntu Base Image: L4T usually uses Ubuntu 20.04 or 22.04 LTS
- Tegra Drivers: GPU, ISP, CSI camera, I2C, SPI, PWM
- Bootloader Stack: U-Boot, CBoot, extlinux
- CUDA Toolkit: GPU-accelerated computing framework
- TensorRT: Inference optimizer and runtime
- cuDNN: Deep neural network acceleration libraries
- Multimedia API: V4L2, GStreamer, OpenMAX for camera and audio
🧬 Architecture:¶
- Jetson boots via UEFI or CBoot into Linux kernel
- Kernel loads NVIDIA drivers (GPU, CPU governors, DeepSleep)
- Device tree manages hardware layout (CPU/GPU/I/O)
- Userland launches graphical UI or SSH terminal
🔍 L4T Version Check:¶
sjsujetson@sjsujetson-01:~$ head -n 1 /etc/nv_tegra_release
# R36 (release), REVISION: 4.3, GCID: 38968081, BOARD: generic, EABI: aarch64, DATE: Wed Jan 8 01:49:37 UTC 2025
This shows JetPack version and internal driver details.
💻 Popular Linux Commands¶
| Command | Description |
|---|---|
ls |
List files in a directory |
cd |
Change directory |
pwd |
Print working directory |
cp / mv / rm |
Copy, move, remove files |
top / htop |
Monitor system processes |
cat / less |
View file content |
sudo |
Run command with admin privileges |
apt |
Install or update software packages |
chmod / chown |
Change file permissions/ownership |
journalctl |
View system logs (via systemd) |
dmesg |
Print kernel ring buffer (boot logs) |
lscpu, lsblk |
List hardware info (CPU/disk) |
🧪 Lab Exercise: Advanced Linux Practice on Jetson¶
Step 1: File System Exploration¶
cd /
ls -lh
ls -lh /dev /proc /sys /boot /media
Step 2: System Monitoring and Processes¶
top
htop # Already installed, If not installed: sudo apt install htop
ps aux | grep python
Step 3: Examine Kernel and Drivers¶
sjsujetson@sjsujetson-01:~$ uname -r
5.15.148-tegra
sjsujetson@sjsujetson-01:~$ lsmod | grep nvgpu
nvgpu 2654208 23
host1x 180224 6 host1x_nvhost,host1x_fence,nvgpu,tegra_drm,nvidia_drm,nvidia_modeset
mc_utils 16384 3 nvidia,nvgpu,tegra_camera_platform
nvmap 204800 79 nvgpu
sjsujetson@sjsujetson-01:~$ cat /proc/device-tree/model
NVIDIA Jetson Orin Nano Engineering Reference Developer Kit Super
Step 4: Explore L4T Features¶
sjsujetson@sjsujetson-01:~$ head -n 1 /etc/nv_tegra_release
# R36 (release), REVISION: 4.3, GCID: 38968081, BOARD: generic, EABI: aarch64, DATE: Wed Jan 8 01:49:37 UTC 2025
sjsujetson@sjsujetson-01:~$ ls /usr/lib/aarch64-linux-gnu/tegra
sjsujetson@sjsujetson-01:~$ nvpmodel -q
NV Power Mode: MAXN_SUPER
2
sjsujetson@sjsujetson-01:~$ tegrastats
07-14-2025 10:29:36 RAM 2147/7620MB (lfb 2x4MB) SWAP 1476/3810MB (cached 1MB) CPU [0%@729,0%@729,0%@729,0%@729,0%@729,0%@729] GR3D_FREQ 0% cpu@47.687C soc2@46.718C soc0@47.468C gpu@48.625C tj@48.625C soc1@48.25C VDD_IN 4556mW/4556mW VDD_CPU_GPU_CV 483mW/483mW VDD_SOC 1451mW/1451mW
Kernel handles VFS (Virtual File System) | |---> Filesystem driver | |---> Disk I/O
Tracing System Calls:¶
strace lets you watch how programs talk to the kernel.
# Install strace
apt install strace
# Trace system calls of a command
strace ls -la
# Trace specific system calls
strace -e trace=open,read,write cat /etc/passwd
# Trace system calls of running process
sudo strace -p <PID>
# Count system calls
strace -c ls -la
🚀 Jetson L4T: In-Depth Technical Analysis¶
🏗️ L4T Architecture Overview¶
L4T (Linux for Tegra) is NVIDIA's comprehensive embedded Linux solution:
┌─────────────────────────────────────────────────────────────┐
│ Applications & Frameworks │
│ TensorRT │ cuDNN │ OpenCV │ GStreamer │ ROS │ Docker │
├─────────────────────────────────────────────────────────────┤
│ CUDA Runtime & Libraries │
│ CUDA Toolkit │ cuBLAS │ cuFFT │ Thrust │ NPP │
├─────────────────────────────────────────────────────────────┤
│ L4T User Space │
│ Ubuntu 20.04/22.04 │ systemd │ NetworkManager │ X11/Wayland│
├─────────────────────────────────────────────────────────────┤
│ L4T Kernel Space │
│ Linux Kernel │ NVIDIA GPU Driver │ Tegra Drivers │
├─────────────────────────────────────────────────────────────┤
│ Bootloader & Firmware │
│ CBoot │ U-Boot │ TOS │ BPMP-FW │ Device Tree │
├─────────────────────────────────────────────────────────────┤
│ Tegra SoC Hardware │
│ ARM CPU │ NVIDIA GPU │ ISP │ VIC │ NVENC │ NVDEC │ I/O │
└─────────────────────────────────────────────────────────────┘
📦 L4T Components Deep Dive¶
1. Bootloader Chain¶
# Check bootloader information
sjsujetson@sjsujetson-01:~$ cat /proc
root=PARTUUID=2eea7ca9-2b58-4100-80a1-ba1b97bdc52b rw rootwait rootfstype=ext4 mminit_loglevel=4 console=ttyTCU0,115200 firmware_class.path=/etc/firmware fbcon=map:0 nospectre_bhb video=efifb:off console=tty0 bl_prof_dataptr=2031616@0x271E10000 bl_prof_ro_ptr=65536@0x271E00000
# View boot configuration
sjsujetson@sjsujetson-01:~$ ls -la /boot/extlinux/
total 24
drwxr-xr-x 2 root root 4096 Jun 22 14:24 .
drwxr-xr-x 5 root root 12288 Jun 22 15:19 ..
-rw-r--r-- 1 root root 938 Jun 22 14:24 extlinux.conf
-rw-r--r-- 1 root root 727 Apr 21 10:59 extlinux.conf.nv-update-extlinux-backup
sjsujetson@sjsujetson-01:~$ cat /boot/extlinux/extlinux.conf
TIMEOUT 30
DEFAULT primary
MENU TITLE L4T boot options
LABEL primary
MENU LABEL primary kernel
LINUX /boot/Image
INITRD /boot/initrd
APPEND ${cbootargs} root=PARTUUID=2eea7ca9-2b58-4100-80a1-ba1b97bdc52b rw rootwait rootfstype=ext4 mminit_loglevel=4 console=ttyTCU0,115200 firmware_class.path=/etc/firmware fbcon=map:0 nospectre_bhb video=efifb:off console=tty0
# Check boot partition
lsblk -f
Boot Sequence: 1. BootROM: Hardware initialization, loads CBoot 2. CBoot: NVIDIA's bootloader, loads kernel and device tree 3. Linux Kernel: Initializes hardware, loads drivers 4. systemd: User space initialization
2. Device Tree and Hardware Configuration¶
# View device tree information
sjsujetson@sjsujetson-01:~$ ls /proc/device-tree/
'#address-cells' dsu-pmu2 regulator-vdd-1v1-hub soc1-throttle-alert
aliases firmware regulator-vdd-1v8-ao soc2-throttle-alert
bpmp gpio-keys regulator-vdd-1v8-hs soctherm-oc-event
bus@0 gpu-throttle-alert regulator-vdd-1v8-sys sound
camera-ivc-channels hot-surface-alert regulator-vdd-3v3-ao sram@40000000
chosen interrupt-parent regulator-vdd-3v3-pcie __symbols__
compatible mgbe-vm-irq-config regulator-vdd-3v3-sd tegra-capture-vi
cpus model regulator-vdd-3v3-sys tegra-carveouts
cpu-throttle-alert name regulator-vdd-5v0-sys tegra-hsp@b950000
cv0-throttle-alert nvpmodel reserved-memory tegra_mce@e100000
cv1-throttle-alert opp-table-cluster0 rtcpu@bc00000 tegra-rtcpu-trace
cv2-throttle-alert opp-table-cluster1 scf-pmu thermal-zones
dce@d800000 opp-table-cluster2 serial timer
display@13800000 pmu serial-number tsc_sig_gen@c6a0000
dsu-pmu0 psci '#size-cells' vm-irq-config
dsu-pmu1 pwm-fan soc0-throttle-alert
sjsujetson@sjsujetson-01:~$ cat /proc/device-tree/model
NVIDIA Jetson Orin Nano Engineering Reference Developer Kit Super
sjsujetson@sjsujetson-01:~$ cat /proc/device-tree/compatible
nvidia,p3768-0000+p3767-0005-supernvidia,p3767-0005nvidia,tegra234
3. NVIDIA GPU Driver Architecture¶
# Check GPU driver version
sjsujetson@sjsujetson-01:~$ cat /proc/driver/nvidia/version
NVRM version: NVIDIA UNIX Open Kernel Module for aarch64 540.4.0 Release Build (buildbrain@mobile-u64-6336-d8000) Tue Jan 7 17:35:12 PST 2025
GCC version: collect2: error: ld returned 1 exit status
# View GPU device information
sjsujetson@sjsujetson-01:~$ ls -la /dev/nvidia*
crw-rw-rw- 1 root root 195, 0 Dec 31 1969 /dev/nvidia0
crw-rw-rw- 1 root root 195, 255 Dec 31 1969 /dev/nvidiactl
crw-rw-rw- 1 root root 195, 254 Dec 31 1969 /dev/nvidia-modeset
4. Tegra-Specific Drivers and Services¶
# List Tegra-specific kernel modules
sjsujetson@sjsujetson-01:~$ lsmod | grep tegra
sjsujetson@sjsujetson-01:~$ lsmod | grep nvgpu
nvgpu 2654208 23
host1x 180224 6 host1x_nvhost,host1x_fence,nvgpu,tegra_drm,nvidia_drm,nvidia_modeset
mc_utils 16384 3 nvidia,nvgpu,tegra_camera_platform
nvmap 204800 79 nvgpu
sjsujetson@sjsujetson-01:~$ lsmod | grep nvhost
# Check Tegra driver information
modinfo tegra_xudc
modinfo nvgpu
# View Tegra-specific devices
ls -la /dev/tegra*
ls -la /dev/nvhost*
🔌 Hardware Access and Driver Interface¶
/opt/nvidia/jetson-io/jetson-io.py is a tool to configure 40-pin header from Nvidia.
1. GPIO (General Purpose Input/Output)¶
GPIO (General Purpose Input/Output) pins allow the Jetson board to interface with external hardware such as LEDs, buttons, sensors, and relays. Each pin can be configured as either: - Input – to read digital signals (e.g. button press) - Output – to send digital signals (e.g. turn on an LED)
On modern Jetson platforms, using libgpiod is generally better and more future-proof than using the older sysfs (/sys/class/gpio) GPIO interface.
# Install gpiod via sudo apt install gpiod (already installed)
#Discover GPIO chips:
sjsujetson@sjsujetson-01:~$ gpiodetect
gpiochip0 [tegra234-gpio] (164 lines)
gpiochip1 [tegra234-gpio-aon] (32 lines)
#List lines on a chip:
sjsujetson@sjsujetson-01:~$ gpioinfo gpiochip0
gpiochip0 - 164 lines:
line 0: "PA.00" "regulator-vdd-3v3-sd" output active-high [used]
line 1: "PA.01" unused input active-high
....
Physical Pin 7 on the 40-pin header is connected to GPIO3_PBB.00. That corresponds to GPIO line 84 on gpiochip0 (according to NVIDIA’s Orin Nano mapping).
sjsujetson@sjsujetson-01:~$ gpioinfo gpiochip0 | grep -i 84
line 84: "PN.00" unused input active-high
#Temporarily Set Line 84 to Output & Drive High:
gpioset gpiochip0 84=1 #automatically requests the line as output, sets it HIGH, and releases it after execution.
#To hold the output state (e.g., keep LED on), use the --mode=wait flag
gpioset --mode=wait gpiochip0 84=1
if use Python (with libgpiod): sudo apt install python3-libgpiod
Jetson.GPIO is another popular GPIO python library developed by Nvidia, but it uses sysfs (deprecated), which is deprecated in the Linux kernel since 4.8, and removed in Linux 5.10+.
2. I2C (Inter-Integrated Circuit)¶
# List I2C buses
sjsujetson@sjsujetson-01:~$ ls /dev/i2c-*
/dev/i2c-0 /dev/i2c-1 /dev/i2c-2 /dev/i2c-4 /dev/i2c-5 /dev/i2c-7 /dev/i2c-9
sjsujetson@sjsujetson-01:~$ i2cdetect -l
i2c-0 i2c 3160000.i2c I2C adapter
i2c-1 i2c c240000.i2c I2C adapter
i2c-2 i2c 3180000.i2c I2C adapter
i2c-4 i2c Tegra BPMP I2C adapter I2C adapter
i2c-5 i2c 31b0000.i2c I2C adapter
i2c-7 i2c c250000.i2c I2C adapter
i2c-9 i2c NVIDIA SOC i2c adapter 0 I2C adapter
# Scan I2C bus for devices (bus 1)
i2cdetect -y 1
smbus2 library to use Python for I2C.
3. SPI (Serial Peripheral Interface)¶
# Check SPI devices
sjsujetson@sjsujetson-01:~$ ls /dev/spidev*
/dev/spidev0.0 /dev/spidev0.1 /dev/spidev1.0 /dev/spidev1.1
4. PWM (Pulse Width Modulation)¶
# Check PWM chips
sjsujetson@sjsujetson-01:~$ ls /sys/class/pwm/
pwmchip0 pwmchip1 pwmchip2 pwmchip3 pwmchip4
Controlling PWM (Pulse Width Modulation) on NVIDIA Jetson (e.g., Orin Nano, Xavier NX, Nano) in Python requires configuring the correct pins and using the Linux PWM sysfs interface or pwmchip character devices.
📹 Camera and Multimedia Subsystem¶
1. Camera Interface (CSI)¶
# List video devices
ls /dev/video*
#sudo apt install v4l-utils
v4l2-ctl --list-devices
# Get camera capabilities
v4l2-ctl -d /dev/video0 --all
v4l2-ctl -d /dev/video0 --list-formats-ext
# Capture image using GStreamer
gst-launch-1.0 nvarguscamerasrc ! 'video/x-raw(memory:NVMM),width=1920,height=1080' ! nvjpegenc ! filesink location=test.jpg
# Live camera preview
gst-launch-1.0 nvarguscamerasrc ! 'video/x-raw(memory:NVMM),width=1280,height=720' ! nvvidconv ! xvimagesink
Python Camera Example:
#!/usr/bin/env python3
import cv2
import numpy as np
def gstreamer_pipeline(
capture_width=1280,
capture_height=720,
display_width=640,
display_height=480,
framerate=30,
flip_method=0,
):
return (
"nvarguscamerasrc ! "
"video/x-raw(memory:NVMM), "
"width=(int)%d, height=(int)%d, "
"format=(string)NV12, framerate=(fraction)%d/1 ! "
"nvvidconv flip-method=%d ! "
"video/x-raw, width=(int)%d, height=(int)%d, format=(string)BGRx ! "
"videoconvert ! "
"video/x-raw, format=(string)BGR ! appsink"
% (
capture_width,
capture_height,
framerate,
flip_method,
display_width,
display_height,
)
)
# Create camera capture
cap = cv2.VideoCapture(gstreamer_pipeline(), cv2.CAP_GSTREAMER)
if not cap.isOpened():
print("Cannot open camera")
exit()
try:
while True:
ret, frame = cap.read()
if not ret:
break
# Display frame
cv2.imshow('Jetson Camera', frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
except KeyboardInterrupt:
pass
finally:
cap.release()
cv2.destroyAllWindows()
⚡ Power Management and Performance¶
1. Power Models (nvpmodel)¶
# Check current power model
sjsujetson@sjsujetson-01:~$ nvpmodel -q
NV Power Mode: MAXN_SUPER
2
# List available power models
nvpmodel -q --verbose
# Set power model (requires sudo)
sudo nvpmodel -m 0 # Maximum performance
sudo nvpmodel -m 1 # Balanced
sudo nvpmodel -m 2 # Power saving
# Check power model configuration
cat /etc/nvpmodel.conf
2. CPU Frequency Scaling¶
# Check CPU frequency information
sjsujetson@sjsujetson-01:~$ lscpu | grep MHz
CPU max MHz: 1728.0000
CPU min MHz: 115.2000
# View CPU frequency scaling governors
cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_available_governors
# Set CPU governor (requires sudo)
echo performance | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
echo powersave | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
# Check current CPU frequencies
cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq
3. GPU Frequency and Power¶
# Check GPU frequency
cat /sys/kernel/debug/bpmp/debug/clk/gpcclk/rate
cat /sys/kernel/debug/bpmp/debug/clk/gpcclk/state
# Monitor GPU usage
sudo tegrastats --interval 1000
# Check thermal zones
cat /sys/class/thermal/thermal_zone*/type
cat /sys/class/thermal/thermal_zone*/temp
🛠️ Advanced System Administration¶
📊 System Monitoring and Debugging¶
1. Process and Resource Monitoring¶
# Advanced process monitoring
top -H # Show threads
htop -t # Tree view
iotop # I/O monitoring
iftop # Network monitoring
# Process tree
pstree -p
pstree -u # Show users
# Detailed process information
ps aux --forest
ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%cpu
# Memory analysis
cat /proc/meminfo
free -h
vmstat 1 5 # Virtual memory statistics
# Disk I/O statistics
iostat -x 1 5
lsof +D /path/to/directory # Files open in directory
2. System Logs and Debugging¶
# systemd journal
journalctl -f # Follow logs
journalctl -u service_name # Service-specific logs
journalctl --since "2024-01-01" --until "2024-01-02"
journalctl -p err # Error level and above
# Kernel logs
dmesg | tail -50
dmesg -T # Human-readable timestamps
dmesg -l err,warn # Error and warning levels
# System logs
tail -f /var/log/syslog
tail -f /var/log/kern.log
# Boot analysis
systemd-analyze
systemd-analyze blame # Service startup times
systemd-analyze critical-chain # Critical path
3. Network Diagnostics¶
# Network interface configuration
ip addr show
ip route show
ip link show
# Network connectivity
ping -c 4 google.com
traceroute google.com
mtr google.com # Continuous traceroute
# Port scanning and connections
nmap -sT localhost
ss -tuln # Socket statistics
netstat -tuln # Network connections
lsof -i :22 # Processes using port 22
# Network traffic analysis
sudo tcpdump -i eth0 -n
sudo tcpdump -i any port 22
🔧 Package Management and Software Installation¶
1. APT Package Manager¶
# Update package lists
sudo apt update
# Upgrade packages
sudo apt upgrade
sudo apt full-upgrade
# Search packages
apt search keyword
apt show package_name
# Install packages
sudo apt install package_name
sudo apt install ./local_package.deb
# Remove packages
sudo apt remove package_name
sudo apt purge package_name # Remove config files too
sudo apt autoremove # Remove unused dependencies
# Package information
dpkg -l | grep package_name
dpkg -L package_name # List files in package
dpkg -S /path/to/file # Find package containing file
2. Snap Package Manager¶
# List installed snaps
snap list
# Search snaps
snap find keyword
# Install snap
sudo snap install package_name
# Update snaps
sudo snap refresh
sudo snap refresh package_name
# Remove snap
sudo snap remove package_name
# Snap information
snap info package_name
3. Building from Source¶
# Install build tools
sudo apt install build-essential cmake git
# Example: Building a simple C program
cat > hello.c << EOF
#include <stdio.h>
int main() {
printf("Hello, Jetson!\n");
return 0;
}
EOF
# Compile
gcc -o hello hello.c
./hello
# Example: CMake project
mkdir build && cd build
cmake ..
make -j$(nproc)
sudo make install
🔐 Security and User Management¶
👥 User and Group Management¶
# User information
id
whoami
groups
w # Who is logged in
last # Login history
# Create user
sudo useradd -m -s /bin/bash newuser
sudo passwd newuser
# Modify user
sudo usermod -aG sudo newuser # Add to sudo group
sudo usermod -s /bin/zsh newuser # Change shell
# Delete user
sudo userdel -r newuser # Remove home directory too
# Group management
sudo groupadd newgroup
sudo usermod -aG newgroup username
sudo gpasswd -d username groupname # Remove from group
🔒 File Permissions and Security¶
# File permissions
ls -la
stat filename
# Change permissions
chmod 755 filename # rwxr-xr-x
chmod u+x filename # Add execute for user
chmod g-w filename # Remove write for group
chmod o=r filename # Set read-only for others
# Change ownership
sudo chown user:group filename
sudo chown -R user:group directory/
# Special permissions
chmod +t directory/ # Sticky bit
chmod g+s directory/ # Set GID
chmod u+s filename # Set UID (SUID)
# Access Control Lists (ACL)
getfacl filename
setfacl -m u:username:rw filename
setfacl -x u:username filename
🛡️ System Security¶
# Firewall (UFW)
sudo ufw status
sudo ufw enable
sudo ufw allow 22/tcp # SSH
sudo ufw allow 80/tcp # HTTP
sudo ufw deny 23/tcp # Telnet
sudo ufw delete allow 80/tcp
# SSH security
sudo systemctl status ssh
sudo nano /etc/ssh/sshd_config
# Recommended changes:
# PermitRootLogin no
# PasswordAuthentication no
# PubkeyAuthentication yes
sudo systemctl restart ssh
# Generate SSH key pair
ssh-keygen -t ed25519 -C "your_email@example.com"
cat ~/.ssh/id_ed25519.pub # Public key
# System updates and security
sudo apt update && sudo apt upgrade
sudo apt install unattended-upgrades
sudo dpkg-reconfigure unattended-upgrades