My persistent USB installation has what looks to be the same file structure in / as it does in /rofs .

Right now /dev/loop0 is out of space.

/dev/loop0 is mounted to /rofs

I can't find info on /rofs , but since the same subdirectories exist at / seems like I could eliminate one or the other to free up space.

What is /dev/loop0 ?
What is /rofs?