I was experimenting with an RTL-SDR on FreeBSD. I could run rtl_tcp on Linux as a regular user but not on FreeBSD. Checking the mode and no group or world permission bits were set.

crw-------  1 root  operator  0x2b May 30 08:58 /dev/usb/0.1.0

I needed at least group permissions. Because rtl_tcp is getting data from the outside world I opted for a separate user for only that. Conveniently, an example very similar to this was in the manpage for devfs.rules(5). First I created a usb user and group and now need to allow it to read USB devices.

USB devices appear in /dev/usb so that path is what need to be used in the rules. The name can be anything while the number is the ID of the rules. Add this to /etc/devfs.rules:

add path 'usb/*' mode 0660 group usb

Those new rules have to be enabled using that name. Add this to /etc/rc.conf:


To make the new rules take effect, devfs needs to be restarted:

/etc/rc.d/devfs restart

Now, this is what the USB device looks like:

crw-rw----  1 root  usb  0x2e May 30 07:59 /dev/usb/0.1.0