If you do not want rar2fs to modify your files when opening, make sure /source is ro
docker run \ -d \ --init \ --name rar2fs \ --cap-add MKNOD \ --cap-add SYS_ADMIN \ --device /dev/fuse \ --network none \ --security-opt apparmor:unconfined \ -v /volume1/rarfiles:/source:ro \ -v /volume1/unrarred:/destination:rshared \ zimme/rar2fs