Manual Pages  — DEVFS.CONF

It does not work for devices plugged in and out after the system is up and running, e.g.amp; USB devices. See devfs.rules(5) for setting ownership and permissions for all device nodes, and devd.conf(5) for actions to be taken when devices are attached or detached.

Lines starting with a hash sign (‘#’) and empty lines are ignored. The lines that specify devfs.conf rules consist of three parameters separated by whitespace:

action
	The action to take for the device. The action names are only significant to the first unique character.
devname
	The name of the device created by devfs(5).
arg	The argument of the action.

The actions currently supported are:

link	This action creates a symbolic link named arg that points to devname, the name of the device created by devfs(5).
own	This action changes the ownership of devname. The arg parameter must be in the form of an owner:group pair, in the same format used by chown(8).
perm	This action changes the permissions of devname. The arg parameter must be a mode as explained in chmod(1).

link    cd0     cdrom

Similarly, to link /dev/cdrom to the first SCSI CD-ROM device, the following action may be used:

link    cd0     cdrom

To set the owner of a device, the own action may be specified:

own     cd0     root:cdrom

To set the permissions of a device, a perm action should be used:

perm    cd0     0660