I had a thumb drive that was mounting on my Ubuntu laptop OK, but was writable only by root.
Long story short, I figured out it was something about the way it was formatted. When I tried to put the same thumb drive into my Mac, it wouldn't mount it and I had to reformat it. After that it mounted just fine on my Ubuntu laptop and was owned by when when I did so.
Not sure how I formatted it in the first place, but lesson learned is that certain formats mount OK but will not be user writable.
Long story short, I figured out it was something about the way it was formatted. When I tried to put the same thumb drive into my Mac, it wouldn't mount it and I had to reformat it. After that it mounted just fine on my Ubuntu laptop and was owned by when when I did so.
Not sure how I formatted it in the first place, but lesson learned is that certain formats mount OK but will not be user writable.