This is the most powerful primitive: it tells modprobe to run your command instead of inserting the module in the kernel as normal.
So you are basically saying the kernel "Hey, if you ever want to insert the hfs module, just run /bin/true instead of the command you would have run. It will insert and configure the module, honest."
According to the
modprobe.d(5)
man page:So you are basically saying the kernel "Hey, if you ever want to insert the
hfs
module, just run/bin/true
instead of the command you would have run. It will insert and configure the module, honest."