TX2 jetpack 4.2 Restart often requires input username and password

jetpack 4.2 Restart often requires input of username and password like this :

anyone know what happen?

it likes set the linux window in frist time on the purple interface.

Under R32.1 (SDKM4.2) there is no initial user account (that’s an Ubuntu 18.04 thing). The first boot is used to add an admin user. Unless the user is added there is no name to display. I think NVIDIA is working to change that for their next release.