How to Access the Boot Menu of NVIDIA Jetson Xavier NX Developer Kit

To access the boot configuration on an NVIDIA Jetson Xavier NX, you must use a serial console connection via the UART header or enter recovery mode by holding the RECOVERY button while powering on. The device does not feature a standard PC-style UEFI menu accessible via keyboard shortcuts like F9 or Esc during POST.

Understanding the Boot Architecture

The NVIDIA Jetson Xavier NX is an embedded system-on-module (SoM) designed for edge AI and robotics applications. Unlike traditional personal computers that rely on a Universal Extensible Firmware Interface (UEFI) with a graphical pre-boot environment, the Jetson platform uses a specialized bootloader called U-Boot. This bootloader is tightly integrated with the NVIDIA Tegra SoC architecture and handles hardware initialization before handing off control to the Linux kernel. Because there is no graphical BIOS/UEFI interface, you cannot simply press a key during startup to select a boot device or change settings in a visual menu. Instead, interaction with the bootloader occurs through a text-based serial console or by manipulating physical hardware states to force specific boot modes. This distinction is critical for developers who are accustomed to desktop PC troubleshooting methods. Attempting to find a keyboard-accessible menu will result in confusion and wasted time. You must instead interact with the system at the hardware level using either a USB-to-UART bridge or by controlling the power state relative to the recovery pin. For more information on resolving issues where the system fails to reach this stage, see our guide on Troubleshooting Ubuntu Boot Issues: A Guide to Fixing Ubuntu Not Booting Properly.

Method 1: Accessing via Serial Console (UART)

The most direct way to interact with the U-Boot prompt is through the serial port. The Jetson Xavier NX Developer Kit exposes a UART header on the module itself. This method allows you to see real-time boot logs and interrupt the boot process to gain a command-line prompt within U-Boot. To set this up, you need a USB-to-UART bridge adapter capable of 3.3V logic levels. Connect the Ground (GND), Transmit (TX), and Receive (RX) pins from the adapter to the corresponding pins on the Jetson module's UART header. Ensure that TX connects to RX and RX connects to TX to allow two-way communication. Once connected, open a terminal emulator such as minicom, screen, or putty on your host computer. Select the correct serial device node, typically /dev/ttyUSB0 or /dev/ttyACM0, and configure the baud rate to 115200 with 8 data bits, no parity, and 1 stop bit. When you power on the Jetson module, watch the terminal window closely. If you see output scrolling rapidly, press any key immediately when prompted. In many default configurations, U-Boot will pause for a few seconds waiting for user input. If you catch this window, you will be dropped into the U-Boot> prompt. From here, you can execute commands to modify boot variables, such as changing the kernel image path or adjusting console output settings. Note that if the system boots too quickly, you may need to adjust the timeout setting in the U-Boot source code or use a script to send the interrupt signal automatically.

Method 2: Entering Recovery Mode

If you do not have a serial cable handy or if the serial console is unresponsive, you can force the Jetson into Recovery Mode. This mode is primarily used for flashing software onto the device using the host computer, but it also provides a pathway to access low-level boot configurations. In this mode, the Jetson appears as a USB device to the host PC, allowing you to communicate with the bootloader over USB. First, ensure your Jetson Xavier NX is completely powered off. Locate the RECOVERY button on the developer kit. This button is often small and may require a pointed object like a paperclip to press. While holding down the RECOVERY button, connect the USB-C cable from the Jetson to your host computer. Continue holding the RECOVERY button for approximately 10 seconds after the host computer detects the new USB device. Then, release the button. On your host machine, run the command lsusb in the terminal. You should see a device listed with the NVIDIA vendor ID, typically appearing as "NVIDIA Corp." or similar. This confirms that the Jetson is in forced recovery mode. To interact with the bootloader in this state, you typically use NVIDIA’s SDK Manager or the flash.sh script provided in the JetPack SDK. These tools communicate with the U-Boot instance running in recovery mode to perform tasks that would otherwise require serial access. This method is particularly useful if you need to re-flash the system partition or recover from a corrupted bootloader state.

Common Configuration Tasks

Once you have access to the U-Boot prompt via serial or recovery mode, you can perform several common administrative tasks. One frequent requirement is changing the default boot argument list. You can view the current boot arguments by typing printenv bootargs at the U-Boot prompt. To modify them, use the setenv command followed by the variable name and the new value. For example, to change the console output, you might update the console parameter within bootargs. Another important task is selecting which storage device to boot from. The Jetson Xavier NX supports eMMC, SD cards, and external NVMe drives. You can specify the boot source using the bootcmd variable. However, be cautious when modifying these variables, as incorrect settings can render the device unbootable. Always backup the current environment variables using saveenv only after verifying your changes, or better yet, document the original values before making edits. For deeper insights into how the system loads modules during this phase, refer to Understanding the Loading of Modules by initramfs in Linux.

Troubleshooting Connection Issues

If you cannot establish a serial connection, verify your wiring. A common mistake is connecting the TX pin to TX instead of RX. Also, ensure that the voltage levels match; connecting a 5V UART adapter to a 3.3V Jetson header without level shifting can damage the module. If using a virtual machine for your host computer, ensure that the USB serial adapter is properly passed through to the VM guest OS. In cases where the serial console shows garbage characters, check the baud rate setting. While 115200 is the standard, some custom builds may use different rates. If the system boots instantly without giving you time to interrupt, consider adding a delay in the U-Boot configuration or using a hardware flow control line if available on your adapter.

Frequently Asked Questions

Can I use the F2 or Del key to enter the BIOS?

No, the Jetson Xavier NX does not have a traditional BIOS or UEFI interface accessible via keyboard keys. It relies on U-Boot, which requires serial console interaction or physical button presses to access configuration menus.

What baud rate should I use for the serial connection?

The standard baud rate for the Jetson Xavier NX UART console is 115200. You should configure your terminal emulator with 8 data bits, no parity, and 1 stop bit (8N1).

How do I exit the U-Boot prompt and continue booting?

You can usually resume the normal boot process by typing boot at the U-Boot prompt. If you accidentally interrupted the boot sequence and want to let it proceed automatically, wait for the countdown timer to expire, though this depends on the specific timeout settings configured in the bootloader.

Is it safe to modify U-Boot environment variables?

Modifying U-Boot variables can be risky if done incorrectly, as it may prevent the system from booting. Always note down the original values before making changes, and avoid saving the environment until you are confident the new settings work correctly.

Why does my Jetson not appear in lsusb when I hold the recovery button?

Ensure you are holding the RECOVERY button for at least 10 seconds after plugging in the USB cable. If it still does not appear, try a different USB cable or port, as some cables are charge-only and do not support data transfer.