Just a short article on how you can select the boot device from the serial console of a NVIDIA Jetson Development Kit. Looky here:
In the last few articles, we covered attaching external storage to the Jetson TX1. We then point the root directory so that during boot time the Jetson runs from external storage. This helps expand the amount of storage on the root device past that of the 16 GB of the internal eMMC.
The serial console is wired into the Jetson TX1 using a USB-TO-TTL serial cable. On a Jetson TK1, the wiring to the serial console is different, but the process on the connected host is the same.
Modifying the extlinux.conf file on the Jetson allows for different booting options to be made available over the serial console. Each device entry has a MENU LABEL which represents the device and is presented to the user during boot over the serial console. On the connected host machine, tapping a key while the Jetson is booting allows us to select the boot device option.
And I would do this why?
There are a few of reasons you may want to use this capability. First, you may want to use it if you need to debug your extlinux.conf file when you change it. The next couple of reasons are for the case when external storage is being used as the root device.
The second reason to use this method is in the case where the root device gets buggered, but you still need to be able to access the Jetson. By having a clean internal eMMC installation, you should be able to boot to the internal eMMC and still be able to examine the other external devices. This provides a margin of comfort in case there are issues and the Jetson won’t boot.
Another reason is that some boot devices are removable media, such as USB drives. Especially when the Jetson is in a space where different people use it, it’s not uncommon for the USB drive to be mistakenly removed and taken away. Without the USB device, the Jetson won’t boot, and the console output may make it look like the Jetson is hopelessly broken. Using the serial console, you can at least boot to the internal eMMC.
Having a SD Card that is a boot device is another safety backup, as the Jetson will attempt to boot from the SD Card before it try to boot from other devices.