Boot from sd

Introduction
sudo ./flash.sh mmcblk1p1
 * Here's tutorial to copy the root file system to SD card, and booting from the SD card.
 * If the root file system will be on an SD card, execute the below script to flash the device -  mentioned at Jetson TX1 and TX2 developer kits user guide

Pick a device to place your rootfs

 * Use these procedures to copy the file system to the Tegra device.
 * 1) If you are using the internal EMMC, skip ahead to Flashing the Bootloader and Kernel.
 * 2) If you prefer to use an external storage device for the root filesystem, use the following procedure to copy the file system to an external storage device.
 * Plug your rootfs device into the host system, If your device is not formatted as Ext4, enter the following command to format it with an Ext4 file system:

$ sudo mkfs.ext4 /dev/sd  Where: is the port to which your device is mounted.  is the device number of the device attached to the port. You can use the dmesg command to determine the port.
 * If needed, mount your device with the following command:

sudo mount /dev/sdX1 Where is the mount point on the host system for your rootfs device.
 * Copy the file system. If LDK_ROOTFS_DIR is set, execute these commands:

$ cd ${LDK_ROOTFS_DIR} $ sudo cp -a * && sync
 * If it is not set, copy the rootfs directory that is included in the release by executing the following commands:

$ cd /Linux_for_Tegra/rootfs $ sudo cp -a * && sync
 * After copying the content to the external disk or device, unmount the disk and connect it to the target Tegra device.
 * unplug SD card and plug-in SD card in TX2
 * modify exlinux.conf in sdcard and boot up the device

change /dev/mmcblk0p1 to /dev/mmcblk1p1 (/boot/extlinux/extlinux.conf)
 * Device is booting using /dev/mmcblk1p1