Just installed Qubes os and somewhere I made my flashdrive read only. The terminal doesn’t recognize the unmount command for me to format a new file system any ideas?
Please choose a better title for this thread and be a bit more descriptive with your issue. This will help the search a lot, so later users can find this thread + the solution.
What exactly happens when you sudo umount /mnt, or what exactly do you execute?
Did you partition your flash drive? If you use it as bought its probably fat32 formatted rn (I think!).
If you want to format it with a new filesystem and its bugging around, I’d recommend removing it, plugging it back in and then doing sth like sudo gparted - which is a nice reasonably simple guy to format it the way you like it.
If you see any error messages please copy paste them into this thread.
Also welcome to the forum and nice to see you use Qubes 
It depends where you are doing it.
It’s not monolithic os, so nothing works as you are used to.
If you are doing it not in machine where it’s connected then you do nothing.
If you attached partition only then you do nothing to whole drive.
So, more info is needed as what you are doing.
And no, “I mounted flash drive” is not a details. It’s like “I’ve flown last year” - that’s a statement not information.