The Jetson team is releasing an updated U-Boot bootloader for L4T 32.1 [JetPack 4.2] to address a possible long term reliability issue for some microSD cards used with the Jetson Nano Developer Kit micro SD card interface.
The Jetson Nano Developer Kit SD Card image based on JetPack 4.2 was updated to include the new U-boot binary and released on 2019/06/07. It is available for download from:
https://developer.nvidia.com/embedded/downloads#?search=SD
Instructions for using the SD card image are here:
https://developer.nvidia.com/embedded/learn/get-started-jetson-nano-devkit#write
If you have a Jetson Nano Developer Kit running JetPack 4.2, you can update only the U-boot binary without rewriting the entire microSD card. The attached zip file contains both the required files and a README with instructions.
To see if your you already have the update, run the following command on your developer kit:
$ sudo strings /dev/disk/by-partlabel/LNX | grep "2016"
The U-boot binary has already been updated if the output matches the below string:
U-Boot 2016.07-g541e96c (May 31 2019 - 15:44:14 -0700)
Note: If the strings command is not available on your developer kit you can get it by using apt-get:
$ sudo apt-get install binutils
r32.1_uboot_update.zip (450 KB)