Hi,
I have Pi3 and I Bought Kingston a400 240gb and sata-usb3 adapter to it. I then downloaded the Hass.io 3.5rc and burned that to the SSD with balenaetcher.
When I plug in the SSD with USB to the Pi 3 and boot, nothing happens. There nothing going on and on the display there is nothing showing.
What I am doing wrong? Are there steps that I have forgot?
This could be interesting: Instructions for USB boot with Hass.io, HassOs and Raspberrypi 3B
Lot of discussion about that issue here. Maybe you use search function…
I did search and could not find a solution. You posted an old link, Hass.io has supported USB boot from 3.4rc that was released on August.
Depending on your pi you might need to set the OTP bit to enable USB boot: https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/msd.md
Also some adapters/SSDs don’t play nice with the Pi. Could be the issue if the above isn’t the issue.
So I first install and run Raspbian and make those changes and then try to boot from SSD that has Hass.io 3.5?
I checked some list for Pi4 usb boot and at least that supports fine the ssd and my adapter.
Yep, that’s correct.
Hmm. The pi4 doesn’t support USB boot yet. What do you mean?
Thanks for the info, will try that.
Pi 4 can be booted from usb if the boot info is still on SD card. So the SD card is only used on boot, otherwise the OS runs on SSD. https://jamesachambers.com/raspberry-pi-4-usb-boot-config-guide-for-ssd-flash-drives/
Right, I thought you were talking about full USB boot. Thought you might be from the future or something. 
It is working now. I had to make 2 changes.
echo program_usb_boot_mode=1 | sudo tee -a /boot/config.txt
But this alone did not work.
echo program_usb_boot_timeout=1 | sudo tee -a /boot/config.txt
Which changes the timeout to 5 seconds. After this change, boot from SSD worked fine.
NOTE: These both changes are permanent and only working for Pi 3 since Pi 4 does not support full USB boot yet!