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
72 utility configures and enables
76 Options indicate an action to be performed:
77 .Bl -tag -width indent
80 This will configure and attach a memory disk with the
81 parameters specified and attach it to the system.
83 Detach a memory disk from the system and release all resources.
85 Select the type of the memory disk.
86 .Bl -tag -width "preload"
88 Storage for this type of memory disk is allocated with
90 This limits the size to the malloc bucket limit in the kernel.
93 option is not set, creating and filling a large
94 malloc-backed memory disk is a very easy way to
99 becomes the backing store for this memory disk.
101 Storage for this type of memory disk is allocated from buffer
103 Pages get pushed out to the swap when the system is under memory
104 pressure, otherwise they stay in the operating memory.
107 backing is generally preferable over
112 Filename to use for the vnode type memory disk. Options
116 are implied if not specified.
118 List configured devices.
121 display details about that particular device.
123 When printing md device names, print only the unit number without the
126 Size of the memory disk.
128 is the number of 512 byte sectors unless suffixed with a
133 denotes byte, kilobyte, megabyte, gigabyte and terabyte respectively. Options
137 are implied if not specified.
138 .It Fl S Ar sectorsize
139 Sectorsize to use for malloc backed device.
140 .It Fl x Ar sectors/track
141 See the description of the
144 .It Fl y Ar heads/cylinder
153 options can be used to specify a synthetic geometry.
154 This is useful for constructing bootable images for later download to
156 .It Fl o Oo Cm no Oc Ns Ar option
157 Set or reset options.
158 .Bl -tag -width indent
159 .It Oo Cm no Oc Ns Cm async
162 backed devices: avoid
164 for increased performance but
165 at the risk of deadlocking the entire kernel.
166 .It Oo Cm no Oc Ns Cm reserve
167 Allocate and reserve all needed storage from the start, rather than as needed.
168 .It Oo Cm no Oc Ns Cm cluster
169 Enable clustering on this disk.
170 .It Oo Cm no Oc Ns Cm compress
171 Enable/Disable compression features to reduce memory usage.
172 .It Oo Cm no Oc Ns Cm force
173 Disable/Enable extra sanity checks to prevent the user from doing something
174 that might adversely affect the system.
175 .It Oo Cm no Oc Ns Cm readonly
176 Enable/Disable readonly mode.
179 Request a specific unit number for the
181 device instead of automatic allocation.
184 To create a 4 megabyte
187 The name of the allocated unit will be output on stdout like
190 .Dl mdconfig -a -t malloc -s 4m
192 To create a disk named
198 .Dl mdconfig -a -t vnode -f /tmp/boot.flp -u 4
200 To detach and free all resources used by
205 To create a 128MByte swap backed disk, initialize an
207 file system on it, and mount it on
209 .Bd -literal -offset indent
210 mdconfig -a -t swap -s 128M -u 10
216 To create a 5MB file-backed disk
221 .Bd -literal -offset indent
222 dd if=/dev/zero of=somebackingfile bs=1k count=5k
223 mdconfig -f somebackingfile -u 0
231 device out of an ISO 9660 CD image file
235 are implied), using the first available
237 device, and then mount the new memory disk:
238 .Bd -literal -offset indent
239 mount -t cd9660 /dev/`mdconfig -f cdimage.iso` /mnt
251 utility first appeared in
253 as a cleaner replacement for the
261 utility was written by
262 .An Poul-Henning Kamp
263 .Aq phk@FreeBSD.org .