test if external usb is bootable

so I got a external USB drive with the intent to boot off of it for my rasberry pi 3 B HA install (HA = Home Assistant, an image the rasberry pi imager supports). I set the usb boot flag using sd card on my pi3, but it wasn't booting off my external usb drive or giving any image on my monitor. The pi3 boots the HA image from microSD no problem, and the external usb drive is recognized by windows 10 no problem (as a data drive anyways). The external USB drive only shows 1 partition in disk management, but who knows. So I want to rule out that the external usb drive is the problem... by booting off it on a regular computer. Any suggestion on what/how I should image it? I tried rufus imaging reactOS onto it but that failed to boot... before I give up on this drive any other suggestion for how to image it or tips to make it work? I suspect it has something to do with its embedded USB to SATA controller.. which I know nothing about. edit1: I was able to boot ubuntu iso off the external usb drive. edit2: booting off the microsd card into pi, I was able to usb mount the external drive, so the drive is mountable in the pi edit3: I double checked the boot flag, it's fine edit4: I saw a video where they booted off a usb key, so I tried that. no go. I think I can eliminate the external drive and say my rasbery pi 3 B isn't botting off USB properly without a sdcard.

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as far as i know there is a utility image to change boot priority on rpi on rpi imager

you might have to use it

1. You don't see two partition on a Windows PC. The reason for this is that "Windows explorer" can only display partitions with FAT or NTFS filesystem and the second partition created by "Raspberry Pi Imager" is a Linux file system of the type "ext4". The windows PC can show it if you install a ext4 driver in windows or you can see it in Windows "Disk manager". 2. Please describe how you changed the boot flag on your Raspberry Pi 3. And there is a verification procedure to check if the USB boot flag has been set, did you try that?

I found a few articles, they all describe the same procedure

https://www.instructables.com/Booting-Raspberry-Pi-3-B-With-a-USB-Drive/

echo program_usb_boot_mode=1 | sudo tee -a /boot/config.txt to turn it on after reboot

and vcgencmd otp_dump | grep 17: with a result of 17:3020000a that it worked

that is all good, my Rasbery Pie 3 B reports that

I tried both a usb external drive, and a usb stick, both imaged with the Rabery Pie Imager, with regular pi os, neither worked to boot without a sd card

sd card works fine

Do you have a USSB2 flash drive you could test with?

ooooo! I had an epiphony, I tried the sd card in a USB Card reader, and that worked!

lol is that what you just suggested? 😄

All USB3 are not compatible to boot with and thats not only with Raspberry Pi's

Nice, then I can say its your USB disk!

and my usb drive too?

and it is not compatible with Raspberry Pi

does it have to be MBR or can it be GPT?

MBR i think

or I guess the rasberry pi imager takes care of that?

I was able to boot off these keys/drives on a regular windows pc, but as you say maybe they are incompatible with the pi

I will try reformatting and making sure they are MBR

but good to know the boot from usb works if I use a USB flash reader

And Im unsure, have never been into that issue

though now it means I proved everything works independently from each toher 😄

thanks for dropping in to suggest stuff!

Or as I would say "With a compatible USB device"

Your welcome

Next time, when you have a issue, dont just say "I tried" be more detailed from the beginning. That increase the chance to get help.

Just an advice.

okay, thank you.

will do