Updated: 2022/Sep/29
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VNDCONFIG(8) System Manager's Manual VNDCONFIG(8)
NAME
vndconfig - configure vnode disks
SYNOPSIS
vndconfig [-cirvz] [-f disktab] [-t typename] vnode_disk regular_file
[geomspec]
vndconfig -u [-Fv] vnode_disk
vndconfig -l [-m min] [vnode_disk ...]
DESCRIPTION
The vndconfig command configures vnode pseudo disk devices. It will
associate the vnode disk vnode_disk with the regular file regular_file
allowing the latter to be accessed as though it were a disk. Hence a
regular file within the filesystem can be used for swapping or can
contain a filesystem that is mounted in the name space. The vnode_disk
is a special file of raw partition or name of vnode disk like vnd0.
By default, accesses to the file bypass normal mechanisms and thus do not
read from or fill the filesystem cache. Because the typical approach is
to access the file only via vnd(4), or at least to have regular accesses
and vnd(4) accesses separated in time, this is generally not problematic.
This bypassing behavior results in not updating the modification
timestamp of the file. Also, file contents read through the filesystem
(and thus the filesystem's caching layer) may not be the contents written
via this interface, so caution is in order for backups. The -i option
may be useful if it is necessary to avoid inconsistent caching.
Options indicate an action to be performed:
-c Configures the device. If successful, references to vnode_disk
will access the contents of regular_file.
If geomspec is specified, the vnode device will emulate the
specified disk geometry. The format of the geomspec argument is:
secsize/nsectors/ntracks/ncylinders
If geometry is not specified, the kernel will choose a default
based on 1MB cylinders. secsize is the number of bytes per
sector. It must be a power of two, and at least 512. nsectors
is the number of sectors per track. ntracks is the number of
tracks per cylinder. ncylinders is the number of cylinders in
the device.
-F Force unconfiguration if the device is in use. Does not imply
-u.
-f disktab
Specifies that the -t option should look up in disktab instead of
in /etc/disktab.
-i Configure the device to use regular file I/O even when direct I/O
using bmap/strategy would be possible.
-l List the vnd devices and indicate which ones are in use. If one
or more specific vnode_disks are given, then only those will be
described.
-m min Together with -l and if no specific devices are given, causes at
least min devices to be listed. The default for min is 4, but
all vnd devices up to (and sometimes just beyond) the highest
numbered vnd device configured since the system last booted will
be listed. If min is set to 0, then only vnd devices currently
in use will be shown.
-r Configure the device as read-only.
-t typename
If configuring the device, look up typename in /etc/disktab and
use the geometry specified in the entry. This option and the
geomspec argument are mutually exclusive.
-u Unconfigures the device.
-v Print messages to stdout describing actions taken.
-z Assume that regular_file is a compressed disk image in cloop2
format, and configure it read-only. See the vndcompress(1)
manpage on how to create such an image.
If no action option [-clu] is given, -c is assumed.
FILES
/dev/rvnd??
/dev/vnd??
/etc/disktab
EXIT STATUS
vndconfig will exit with status 0 if the operation requested completed
successfully, or 1 otherwise. Unsuccessful completion can be caused by
unknown or incorrectly used options; attempting to configure a vnd that
is already configured; or unconfigure one that is not, or without -F, one
which is still in use; or if devices are specified that do not exist or
are not vnd(4) devices, giving an improper geometry, etc.
EXAMPLES
vndconfig vnd0 /tmp/diskimage
or
vndconfig /dev/rvnd0c /tmp/diskimage
Configures the vnode disk vnd0. Please note that use of the second form
of the command is discouraged because it requires knowledge of the raw
partition which varies between architectures. For the first form, be
aware that there must not be a file vnd0 in the current directory, or it
will be assumed to be the vnd device to be configured (which will usually
fail.)
vndconfig vnd0 /tmp/floppy.img 512/18/2/80
Configures the vnode disk vnd0 emulating the geometry of 512 bytes per
sector, 18 sectors per track, 2 tracks per cylinder, and 80 cylinders
total.
vndconfig vnd0 /tmp/image.udf 2048/1/1/0
Configures the vnode disk vnd0 for an UDF image to be used with
mount_udf(8).
vndconfig -t floppy vnd0 /tmp/floppy.img
Configures the vnode disk vnd0 using the geometry specified in the floppy
entry in /etc/disktab.
vndconfig -u vnd0
Unconfigures the vnd0 device.
To obtain status on all vnd devices listed in /dev (assuming a system
where the `d' partition is the whole device (RAW_PART)), use:
vndconfig -l /dev/vnd*d
Using
vndconfig -m0 -l /dev/vnd*d
will omit those devices that are not in use, whereas
vndconfig -l
will list all devices known to the kernel (at least 4 without -m)
regardless of what might appear in /dev (or elsewhere.)
SEE ALSO
vndcompress(1), opendisk(3), vnd(4), mount(8), swapctl(8), umount(8)
HISTORY
The vnconfig command appeared in NetBSD 1.0. It was renamed to vndconfig
in NetBSD 7.0 for consistency with other similar commands. (The original
name was also retained as an alternative for backwards compatibility.)
NetBSD 10.99 October 20, 2023 NetBSD 10.99