1 .\" Copyright (c) 1993 University of Utah.
2 .\" Copyright (c) 1980, 1989, 1991, 1993
3 .\" The Regents of the University of California. All rights reserved.
5 .\" Poul-Henning Kamp All rights reserved.
7 .\" This code is derived from software contributed to Berkeley by
8 .\" the Systems Programming Group of the University of Utah Computer
9 .\" Science Department.
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39 .\" @(#)vnconfig.8 8.1 (Berkeley) 6/5/93
40 .\" from: src/usr.sbin/vnconfig/vnconfig.8,v 1.19 2000/12/27 15:30:29
49 .Nd configure and enable memory disks
55 .Oo Fl o Oo Cm no Oc Ns Ar option Oc ...
58 .Op Fl S Ar sectorsize
60 .Op Fl x Ar sectors/track
65 .Op Fl o Oo Cm no Oc Ns Ar force
74 utility configures and enables
78 Options indicate an action to be performed:
79 .Bl -tag -width indent
82 This will configure and attach a memory disk with the
83 parameters specified and attach it to the system.
85 Detach a memory disk from the system and release all resources.
87 Select the type of the memory disk.
88 .Bl -tag -width "preload"
90 Storage for this type of memory disk is allocated with
92 This limits the size to the malloc bucket limit in the kernel.
95 option is not set, creating and filling a large
96 malloc-backed memory disk is a very easy way to
101 becomes the backing store for this memory disk.
103 Storage for this type of memory disk is allocated from buffer
105 Pages get pushed out to the swap when the system is under memory
106 pressure, otherwise they stay in the operating memory.
109 backing is generally preferable over
114 Filename to use for the vnode type memory disk. Options
118 are implied if not specified.
120 List configured devices.
123 display details about that particular device.
126 option specified, show all details.
128 When printing md device names, print only the unit number without the
131 Size of the memory disk.
133 is the number of 512 byte sectors unless suffixed with a
138 denotes byte, kilobyte, megabyte, gigabyte and terabyte respectively. Options
142 are implied if not specified.
143 .It Fl S Ar sectorsize
144 Sectorsize to use for malloc backed device.
145 .It Fl x Ar sectors/track
146 See the description of the
149 .It Fl y Ar heads/cylinder
158 options can be used to specify a synthetic geometry.
159 This is useful for constructing bootable images for later download to
161 .It Fl o Oo Cm no Oc Ns Ar option
162 Set or reset options.
163 .Bl -tag -width indent
164 .It Oo Cm no Oc Ns Cm async
167 backed devices: avoid
169 for increased performance but
170 at the risk of deadlocking the entire kernel.
171 .It Oo Cm no Oc Ns Cm reserve
172 Allocate and reserve all needed storage from the start, rather than as needed.
173 .It Oo Cm no Oc Ns Cm cluster
174 Enable clustering on this disk.
175 .It Oo Cm no Oc Ns Cm compress
176 Enable/Disable compression features to reduce memory usage.
177 .It Oo Cm no Oc Ns Cm force
178 Disable/Enable extra sanity checks to prevent the user from doing something
179 that might adversely affect the system.
180 .It Oo Cm no Oc Ns Cm readonly
181 Enable/Disable readonly mode.
184 Request a specific unit number for the
186 device instead of automatic allocation.
189 To create a 4 megabyte
192 The name of the allocated unit will be output on stdout like
195 .Dl mdconfig -a -t malloc -s 4m
197 To create a disk named
203 .Dl mdconfig -a -t vnode -f /tmp/boot.flp -u 4
205 To detach and free all resources used by
210 To create a 128MByte swap backed disk, initialize an
212 file system on it, and mount it on
214 .Bd -literal -offset indent
215 mdconfig -a -t swap -s 128M -u 10
221 To create a 5MB file-backed disk
226 .Bd -literal -offset indent
227 dd if=/dev/zero of=somebackingfile bs=1k count=5k
228 mdconfig -f somebackingfile -u 0
236 device out of an ISO 9660 CD image file
240 are implied), using the first available
242 device, and then mount the new memory disk:
243 .Bd -literal -offset indent
244 mount -t cd9660 /dev/`mdconfig -f cdimage.iso` /mnt
256 utility first appeared in
258 as a cleaner replacement for the
266 utility was written by
267 .An Poul-Henning Kamp
268 .Aq phk@FreeBSD.org .