View source for Jetson/L4T/Boot From External Device

== Introduction ==
* Flash device with rootfs on external devices (USB, SATA, NVMe) or internal device (emmc, sd).
* With new releases >= rel-32, external  is being used as identification is solely on UUID based and not type of media.

== Steps ==
1. Connect the external device to host Linux PC

2. Create GPT and partiton using gdisk on the device:
   $sudo gdisk /dev/sd'''x'''
   "o" -> clear all current partition data
   "n" -> create new partition
   "1" -> partition number /dev/sd'''x'''1
   "40M"first sectors -> Press enter or "+32G" last sectors
   "Linux filsystem" -> using default type
   "c" -> partition's name "PARTLABEL"
   "w" -> write to disk and exit. 

3. Get partition UUID and copy rootfs to the device:
   $ sudo mkfs.ext4 /dev/sd'''x'''1
   // get partition UUID for step 4
   $ sudo blkid /dev/sd'''x'''1
   $ sudo mount /dev/sd'''x'''1 /mnt
   // go to rootfs directory
   $ cd rootfs/
   // copy rootfs
   $ sudo tar -cpf - * | ( cd /mnt/ ; sudo tar -xpf - )
   $ sudo umount /mnt

4. If release < r32.5, create and copy PARTUUID to bootloader/l4t-rootfs-uuid.txt for internal and external device. 
If release >= r32.5, no required PARTUUID, use "nvme0n1p1" flash for external device.

   examples:
   $ sudo ./flash.sh jetson-tx2 nvme0n1p1
5. Flash the board with rootfs device -> external is for nvme, usb, sata while internal is for sdcard/emmc: (for release < r32.5)
   $ sudo ./flash.sh jetson-tx2 external
   $ sudo ./flash.sh jetson-tx2 internal
6. Done

== Use NVMe + Xavier NX as example ==

If you have Xavier NX and the external device is NVMe PCIe M.2 SSD card, you can execute the steps on XNX:

1.1 Plugin the card to M.2 slot on XNX and boot up

1.2 Download packages to XNX and generate rootfs
   // download ''L4T Driver Package (BSP)'' and ''Sample Root Filesystem''
   https://developer.nvidia.com/embedded/linux-tegra
   
   // put the packages in same folder and do
   $ sudo tar xpf Tegra186_Linux_R32.4.4_aarch64.tbz2
   $ cd Linux_for_Tegra/rootfs/
   $ sudo tar xpf ../../Tegra_Linux_Sample-Root-Filesystem_R32.4.4_aarch64.tbz2
   $ cd ../
   $ sudo ./apply_binaries.sh

2. Create GPT and partiton using gdisk on the device:
   $sudo gdisk /dev/nvme0
   "o" -> clear all current partition data
   "n" -> create new partition
   "1" -> partition number /dev/nvme0n1p1
   "40M"first sectors -> Press enter
   "Linux filsystem" -> using default type
   "c" -> partition's name "PARTLABEL"
   "w" -> write to disk and exit. 

3 Get partition UUID and copy rootfs to the device:
   $ sudo mkfs.ext4 /dev/nvme0n1p1
   // on r32.4.4, get partition UUID for step 4; no need for r32.5
   $ sudo blkid /dev/nvme0n1p1
   $ sudo mount /dev/nvme0n1p1 /mnt
   // go to rootfs directory
   $ cd rootfs/
   // copy rootfs
   $ sudo tar -cpf - * | ( cd /mnt/ ; sudo tar -xpf - )
   $ sudo umount /mnt

4. On host Linux PC, copy PARTUUID to bootloader/l4t-rootfs-uuid.txt. This step is not required for r32.5.

5. Flash the board with rootfs device:
   // r32.4.4
   $ sudo ./flash.sh jetson-xavier-nx-devkit-emmc external
   // r32.5
   $ sudo ./flash.sh jetson-xavier-nx-devkit-emmc nvme0n1p1
6. Done

== Check ==
After boot up, the u-boot logs will like below:
 TEGRA186
 Model: NVIDIA P2771-0000-500
 DRAM:  7.8 GiB
 MC:   Tegra SD/MMC: 0, Tegra SD/MMC: 1
 *** Warning - bad CRC, using default environment
 In:    serial
 Out:   serial
 Err:   serial
 Net:   eth0: ethernet@2490000
 Hit any key to stop autoboot:  0 
 switch to partitions #0, OK
 mmc1 is current device
 Scanning mmc 1:1...
 Found /boot/extlinux/extlinux.conf
 Retrieving file: /boot/extlinux/extlinux.conf
 733 bytes read in 127 ms (4.9 KiB/s)
 L4T boot options
 1:	primary kernel
 Enter choice: 1:	primary kernel
 Retrieving file: /boot/initrd
 5564673 bytes read in 697 ms (7.6 MiB/s)
 Retrieving file: /boot/Image
 34179080 bytes read in 3848 ms (8.5 MiB/s)
 append: '''root=PARTUUID=ec27c846-88af-41f6-bd4b-fd46c54bb5ce''' rw rootwait rootfstype=ext4 console=ttyS0,115200n8 console=tty0 fbcon=map:0 net.ifnames=0 
 video=tegrafb no_console_suspend=1 earlycon=uart8250,mmio32,0x3100000 nvdumper_reserved=0x2772e0000 gpt tegra_fbmem2=0x800000@0x9607b000 
 lut_mem2=0x2008@0x96078000 usbcore.old_scheme_first=1 tegraid=18.1.2.0.0 maxcpus=6 boot.slot_suffix= boot.ratchetvalues=0.2031647.1 
 bl_prof_dataptr=0x10000@0x275840000 sdhci_tegra.en_boot_part_access=1 quiet