vnd4

Usage

Overview

The vnd driver provides a disk-like interface to a file. This is useful for a variety of applications, such as building miniroot or floppy disk images.

This document assumes familiarity with how to generate kernels and how to properly configure disks and pseudo-devices in a kernel configuration file.

In order to compile in support for vnd devices, a line similar to the following must be present in the kernel configuration file:

pseudo-device	vnd	4	# vnode disk driver

The count argument is how many vnds memory is allocated for at boot time. In this example, no more than 4 vnds may be configured.

There is a run-time utility that is used for configuring vnds. See vnconfig(8) for more information.

Ioctl interface

The following ioctl(2) calls are defined in ⟨dev/vndioctl.h⟩:

VNDIOCSET struct vnd_ioctl *

Associate the file vnd_file with a vnd pseudo device, optionally encrypted using the Blowfish cipher and the key specified in vnd_key of length vnd_keylen. The size of the configured device is returned in vnd_size.

struct vnd_ioctl {
	char	*vnd_file;
	off_t	vnd_size;
	u_char	*vnd_key;
	int	vnd_keylen;
};

VNDIOCCLR struct vnd_ioctl *

Disassociate a vnd device.

VNDIOCGET struct vnd_user *

Get the associated file name, device, inode number, and unit number of a vnd device. If vnu_unit is -1, information on the vnd device corresponding to the file descriptor passed to ioctl(2) will be returned. Otherwise, vnu_unit may contain the unit number of another vnd device. This allows for opening just vnd0 and querying all available devices.

struct vnd_user {
	char	vnufile[VNDNLEN];
	int	vnu_unit;
	dev_t	vnu_dev;
	ino_t	vnu_ino;
};

Additionally, some disklabel(8) related ioctl(2) calls defined in ⟨sys/dkio.h⟩ are available: DIOCGDINFO, DIOCSDINFO, and DIOCWDINFO. They are documented in sd(4).

Files

/dev/{,r}vnd*

vnd device special files