Nextcloudpi docker container does not recognize external storage

Hi, I want to back up Nextcloudpi docker to a USB storage.

If I use the “–privileged” command when I run the container it recognizes the USB device well (but I don’t like to use this command for security), this is the command I used:

docker run -dit --privileged -d -p 4443:4443 -p 443:443 -p 80:80 -v ncdata:/data --name nextcloudpi abe8u3f83e8a 192.168.0.122

So I tried the command “–device” and it doesn’t work, fdisk doesn’t recognize any partition:

docker run -dit --device=/dev/sda1:/dev/sda1 -d -p 4443:4443 -p 443:443 -p 80:80 -v ncdata:/data --name nextcloudpe abe8u3f83e8a 192.168.0.122

Can anybody help me please?