How to flash a specific partition with Jetson Nano

First of all, I want to add a new sensor in device tree. So according to the Linux Driver Package Development Guide, I plan to download the kernel source code and build out the image and dts files. I have done the above and I don’t know what this means in the Guide:

-On T210 (Nano and TX1) devices only, connect the Jetson device’s recovery USB port to your host. Enter this command at the U‑Boot command prompt:
-ums 0 mmc 1
-This connects eMMC (or the Jetson Nano SD Card) to the host as a set of USB mass storage devices (each partition as a device). You then can copy your custom kernel to /boot/Image directly.

What does “enter this command at the U-Boot command prompt” means? In addition,I have tried to use the sdkmanager to flash the jetson nano. Sdkmanager will automatically download and creat the os image and driver files so I replace the kernel image and dts files with these built from new kernel source code. After flashing, the jetson nano can be configed the user name and password, but it didn’t entering the operating interface after thar and stuck in “started Update UTMP about System Runlevel Changes”.
I don’t know if this way is wrong and I want to try U-Boot way but I don’t how to do it?

hello 623985052,

you could update device tree partition with the flash.sh script file,
please also check the documentation, please access Flashing a Specific Partition session for the steps and commands.
thanks

Thanks JerryChang,
I have read the Flashing a Specific Partition session, it says that command" -K kernel " didn’t work in Jetson Nano, and it says :
Enter this command at the U‑Boot command prompt:
-ums 0 mmc 1

I don’t know what it exactly means.

hello 623985052,

if you would like to update kernel image with the device running with u-boot…
when execute “-k kernel” to flash the board, the image flashed to the kernel partition is actually an u-boot image.
hence, if you would like to update the kernel image, just copy your customize image to the target. you should replace /boot/Image with a custom-built kernel and launch it with u-boot to take effect.

due to Jetson-Nano launching from sd-card. you should execute commands at u-boot to configure as USB mass storage devices. then you’ll able to overwrite /boot/Image directly.
thanks