I installed dduper on my Ubuntu 21.04 system with a BTRFS file system called mounted as /data in /dev/sda1. I'm trying to play around with it on a single directory, but I keep getting permission denied errors.

dduper -p /dev/sda1 --dir /data/G --recurse --dry-run

Tells me ..

ERROR: cannot open '/dev/sda1': Permission denied
unable to open /dev/sda1

Adding sudo in front of dduper doesn't work either.

Any ideas?