I finally got the Pi 4 to boot from the USB SSD!
After hours of trying all sorts of things, e.g. using my new 45W power supply with the Pi 4 and the SSD plugged in directly with no hub (which didn't work) I finally noticed that when it was booted from the SD card with the SSD plugged in directly without the hub, the SSD boot and root partitions were not mounting on the desktop. Then I stumbled across this passage under Hardware Compatibility in the docs: https://www.raspberrypi.com/documentati ... patibility and realised that my SSD is a SATA drive in a USB enclosure, so it was likely that damn UAS issue after all!
So I went through the steps outlined in viewtopic.php?t=245931 and updated cmdline.txt with the necessary quirks setting on the SSD and tried booting from it again and this time it worked!
Unfortunately it only works with the drive plugged directly into the Pi without the hub, connect it via the hub and the boot just hangs at the new boot device selection screen. I tried finding the idVendor and idProduct for the hub and adding them to cmdline.txt but that didn't help so I gave up on the hub and tried booting from the SSD with the Pi 4's 15W power supply instead of the 45W ps from my new Pi 5, and that worked too. (Though I guess that's not likely to work under real world conditions, but at least it booted.)
After hours of trying all sorts of things, e.g. using my new 45W power supply with the Pi 4 and the SSD plugged in directly with no hub (which didn't work) I finally noticed that when it was booted from the SD card with the SSD plugged in directly without the hub, the SSD boot and root partitions were not mounting on the desktop. Then I stumbled across this passage under Hardware Compatibility in the docs: https://www.raspberrypi.com/documentati ... patibility and realised that my SSD is a SATA drive in a USB enclosure, so it was likely that damn UAS issue after all!
So I went through the steps outlined in viewtopic.php?t=245931 and updated cmdline.txt with the necessary quirks setting on the SSD and tried booting from it again and this time it worked!
Unfortunately it only works with the drive plugged directly into the Pi without the hub, connect it via the hub and the boot just hangs at the new boot device selection screen. I tried finding the idVendor and idProduct for the hub and adding them to cmdline.txt but that didn't help so I gave up on the hub and tried booting from the SSD with the Pi 4's 15W power supply instead of the 45W ps from my new Pi 5, and that worked too. (Though I guess that's not likely to work under real world conditions, but at least it booted.)
Statistics: Posted by dshan — Thu Jun 19, 2025 10:30 am