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
73 utility configures and enables
77 Options indicate an action to be performed:
78 .Bl -tag -width indent
81 This will configure and attach a memory disk with the
82 parameters specified and attach it to the system.
84 Detach a memory disk from the system and release all resources.
86 Select the type of the memory disk.
87 .Bl -tag -width "preload"
89 Storage for this type of memory disk is allocated with
91 This limits the size to the malloc bucket limit in the kernel.
94 option is not set, creating and filling a large
95 malloc-backed memory disk is a very easy way to
100 becomes the backing store for this memory disk.
102 Storage for this type of memory disk is allocated from buffer
104 Pages get pushed out to the swap when the system is under memory
105 pressure, otherwise they stay in the operating memory.
108 backing is generally preferable over
113 Filename to use for the vnode type memory disk. Options
117 are implied if not specified.
119 List configured devices.
122 display details about that particular device.
125 option specified, show all details.
127 When printing md device names, print only the unit number without the
130 Size of the memory disk.
132 is the number of 512 byte sectors unless suffixed with a
137 denotes byte, kilobyte, megabyte, gigabyte and terabyte respectively. Options
141 are implied if not specified.
142 .It Fl S Ar sectorsize
143 Sectorsize to use for malloc backed device.
144 .It Fl x Ar sectors/track
145 See the description of the
148 .It Fl y Ar heads/cylinder
157 options can be used to specify a synthetic geometry.
158 This is useful for constructing bootable images for later download to
160 .It Fl o Oo Cm no Oc Ns Ar option
161 Set or reset options.
162 .Bl -tag -width indent
163 .It Oo Cm no Oc Ns Cm async
166 backed devices: avoid
168 for increased performance but
169 at the risk of deadlocking the entire kernel.
170 .It Oo Cm no Oc Ns Cm reserve
171 Allocate and reserve all needed storage from the start, rather than as needed.
172 .It Oo Cm no Oc Ns Cm cluster
173 Enable clustering on this disk.
174 .It Oo Cm no Oc Ns Cm compress
175 Enable/Disable compression features to reduce memory usage.
176 .It Oo Cm no Oc Ns Cm force
177 Disable/Enable extra sanity checks to prevent the user from doing something
178 that might adversely affect the system.
179 .It Oo Cm no Oc Ns Cm readonly
180 Enable/Disable readonly mode.
183 Request a specific unit number for the
185 device instead of automatic allocation.
188 To create a 4 megabyte
191 The name of the allocated unit will be output on stdout like
194 .Dl mdconfig -a -t malloc -s 4m
196 To create a disk named
202 .Dl mdconfig -a -t vnode -f /tmp/boot.flp -u 4
204 To detach and free all resources used by
209 To create a 128MByte swap backed disk, initialize an
211 file system on it, and mount it on
213 .Bd -literal -offset indent
214 mdconfig -a -t swap -s 128M -u 10
220 To create a 5MB file-backed disk
225 .Bd -literal -offset indent
226 dd if=/dev/zero of=somebackingfile bs=1k count=5k
227 mdconfig -f somebackingfile -u 0
235 device out of an ISO 9660 CD image file
239 are implied), using the first available
241 device, and then mount the new memory disk:
242 .Bd -literal -offset indent
243 mount -t cd9660 /dev/`mdconfig -f cdimage.iso` /mnt
255 utility first appeared in
257 as a cleaner replacement for the
265 utility was written by
266 .An Poul-Henning Kamp
267 .Aq phk@FreeBSD.org .