After the first flash system, need to configure the boot initialization，How to start initialization with configuration on serial port，I refer to Headless Mode in oem-config Nvidia document，I usb ckermit or cutecom serial tool， Only printed information is displayed, no prompt for input，
Print part of the information below：
2.851594] tegra-pcie-dw 14120000.pcie: pex_wake already in use
[ 9.224861] tegra-pcie-dw 14140000.pcie: pex_wake already in use
[ 9.739019] tegra-pcie-dw 14160000.pcie: pex_wake already in use
[ 10.256544] tegra-pcie-dw 141a0000.pcie: pex_wake already in use
[ 11.243073] cgroup: cgroup2: unknown option “nsdelegate”
[ 12.481471] random: crng init done
[ 12.481593] random: 7 urandom warning(s) missed due to ratelimiting
[ 77.142878] Please complete system configuration setup on desktop to proceed…
this messages means system waits for your feedback to complete the system configurations, (i.e. user names, password, timezone…etc)
there’ll be ubuntu UI shows-up if you’re having display monitor connected.
if there’s no display device, it runs oem-config in headless mode. for example, Headless Mode Flow in oem-config.
because I know how it helps if it’s clear what to expect, I’ll add my experience.
Before first boot after flash, you can connect your host to the USB3.0 port at power buttons and then after boot establish a serial console connection from host via e.g.
sudo screen /dev/ttyACM0 115200 (for me it actually is ttyACM1).
Try repeatedly over a minute or so if connection fails. Press ENTER some times if connection succeeds but screen is blank. Then you are in the oem-config dialog.
I believe the option to connect to ttyACM can time out, so you need to establish quickly after boot. Otherwise, the /dev/ttyUSB3 console says something about timeout or reset and I just pressed RESET and after reboot could establish connection to ttyACM and walk through oem-config.