Additional info…
The u-boot boot loader normally reads file “extlinux.conf” prior to handing off to the kernel. By default this file is located on eMMC (a.k.a. “mmcblk0p1”) as “/boot/extlinux/extlinux.conf”. In that file are a number of key/value pairs. One of those is the APPEND key, and the value is one very long string which is passed directly to the Linux kernel at the moment of boot. That parameter has its own key/value pairs, one of which starts with “root=”. This tells the kernel where to find the root file system. Should you name a partition on another device, then that device is your root partition from that moment forward.
A basic root partition consists of the sample rootfs unpacked there using proper permissions (meaning you use root or root authority during unpack, and you unpack to an ext4 file system). Following this the driver package script “apply_binaries.sh” can be used to update that sample rootfs to be specific for Jetson hardware (the option format is "sudo ./apply_binaries.sh -r “/wherever/the/ssd/ext4/partition/is/mounted”).
If you want easy testing via serial console you can get details here:
[url]http://elinux.org/Jetson/TX1_Serial_Console[/url]