Initial README

README.md

@@ -1,4 +1,35 @@
 # rootOnNVMe
 Switch the rootfs to a NVMe SSD on the Jetson Xavier NX and Jetson AGX Xavier
 
-# Work in Progress
+These scripts install a service which runs at startup to point the rootfs to a SSD installed on /dev/nvme0 (the M.2 Key M slot).
+
+This is taken from the NVIDIAS Jetson AGX Xavier forum https://forums.developer.nvidia.com/t/how-to-boot-from-nvme-ssd/65147/22, written by user crazy_yorik (https://forums.developer.nvidia.com/u/crazy_yorick). Thank you crazy_yorik!
+
+This procedure should be done on a fresh install of the SD card using JetPack 4.3+. Install the SSD into the M.2 Key M slot of the Jetson, and format it gpt, ext4, and setup a partition (p1). The AGX Xavier uses eMMC, the Xavier NX uses a SD card in the boot sequence.
+
+Next, copy the rootfs of the eMMC/SD card to the SSD
+```
+$ ./copy-rootfs-ssd.sh
+```
+
+Then, setup the service. This will copy the .service file to the correct location, and install a startup script to set the rootfs to the SSD.
+```
+$ ./setup-service.sh
+```
+
+Note that setssdroot.sh is the script for installation, and should not be run individually. After setting up the service, reboot for the changes to take effect.
+
+### Boot Notes
+These script changes the rootfs to the SSD after the kernel image is loaded from the eMMC/SD card. For the Xavier NX, you will still need to have the SD card installed for booting. As of this writing, the default configuration of the Jetson NX does not allow direct booting from the NVMe.
+
+### Upgrading
+Once this service is installed, the rootfs will be on the SSD. If you upgrade to a newer version of L4T using OTA updates (using the NVIDIA .deb repository), you will need to also apply those changes to the SD card that you are booting from.
+
+Typically this involves copying the /boot* directory and /lib/modules/\<kernel name\>/ from the SSD to the SD card. If they are different, then modules load will be 'tainted', that is, the modules version will not match the kernel version.
+
+
+## Notes
+* Initial Release, May 2020
+* JetPack 4.4 DP
+* Tested on Jetson Xavier NX
+