This article is quite old now - I see it’s mentioning it’s for an Rpi 2, but if you’re running RPi3B there is an exceptionally easier way… build up your Openhab install and configuration on your SD card as per normal, then type:
vcgencmd otp_dump | grep 17
It should come back with 17:1020000a (meaning boot off SD card)
Now edit the /boot/config.txt and add to the bottom:
program_usb_boot_mode=1
Save the file, then reboot your Rpi. Once logged back on, run the above command again:
vcgencmd otp_dump | grep 17
It should now come back with 17:3020000a (meaning boot off USB disk - but, it will always try SD first. If it comes back with the original setting, then you either typo’d the entry, or you’re running an older Rpi that doesn’t support booting off USB-to-SSD disk)
Now edit the config.txt file a 2nd time, and remove the program_usb_boot_mode=1 line. Immediately after that, shutdown the RPi:
sudo shutdown now
Remove the SD card, and put it in a USB SD card reader and install in your PC. Download win32diskimager and take an image of the SD card saving to a file on your PC. Once done, unplug your USB SD card reader and plug the SSD disk into your PC (via the USB-to-SSD 3.0 cable you would have bought) and now write the image you took with the win32diskimager back to the SSD disk.
Once complete, plug the USB-to-SSD cable with SSD disk into your RPi and power it up. Voila, you’re now booting from SSD disk, NO SD card needed. Boot up time will be marginally slower as the RPi looks for the SD card initially (5 seconds longer from my testing), but will revert to the USB SSD disk straight after. Note that this process won’t work with most SATA/SAS disks, as being mechanical drives the USB port can’t provide enough grunt to power the drive.
You do NOT need the SD card to boot the RPi with an SSD disk. Some have said an empty SD card will improve the boot speed. In terms of performance, I’ve noticed OH is faster with the SSD disk, even though it’s limited by the USB 2.0 speed of the interface.
In regards to doing OH backups, see my super simple backup script if you happen to be running an FTP server… Super simple OH backup script to FTP server