January 1, 1996 IO 4 i386

### NAME

io - I/O privilege file

### DESCRIPTION

This device is obsolete and is provided for compatibility purposes only; use i386_iopl(2) instead.

After opening ```/dev/io` for writing the process is granted full I/O privileges; closing the returned file descriptor does not result in revocation of these privileges. The new I/O privileges can be useful in order to write userland programs that handle some hardware directly.

The entire access control is handled by the file access permissions of ```/dev/io`, so care should be taken in granting rights for this device.

I/O privilege on access to ```/dev/io` is only granted if the kernel was built with the ```COMPAT_10` option.

### FILES

```/dev/io`

### SEE ALSO

mem(4)

### HISTORY

The io file appeared in NetBSD1.0 after it was in the kernel for some time.