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
61 .Op Fl y Ar heads/cylinder
65 .Op Fl o Oo Cm no Oc Ns Ar force
76 utility configures and enables
80 Options indicate an action to be performed:
81 .Bl -tag -width indent
84 This will configure and attach a memory disk with the
85 parameters specified and attach it to the system.
87 Detach a memory disk from the system and release all resources.
89 Select the type of the memory disk.
90 .Bl -tag -width "preload"
92 Storage for this type of memory disk is allocated with
94 This limits the size to the malloc bucket limit in the kernel.
97 option is not set, creating and filling a large
98 malloc-backed memory disk is a very easy way to
101 A file specified with
103 becomes the backing store for this memory disk.
105 Storage for this type of memory disk is allocated from buffer
107 Pages get pushed out to the swap when the system is under memory
108 pressure, otherwise they stay in the operating memory.
111 backing is generally preferable over
116 Filename to use for the vnode type memory disk. Options
120 are implied if not specified.
122 List configured devices.
125 display details about that particular device.
128 option specified, show all details.
130 When printing md device names, print only the unit number without the
133 Size of the memory disk.
135 is the number of 512 byte sectors unless suffixed with a
140 denotes byte, kilobyte, megabyte, gigabyte and terabyte respectively. Options
144 are implied if not specified.
145 .It Fl S Ar sectorsize
146 Sectorsize to use for malloc backed device.
147 .It Fl x Ar sectors/track
148 See the description of the
151 .It Fl y Ar heads/cylinder
160 options can be used to specify a synthetic geometry.
161 This is useful for constructing bootable images for later download to
163 .It Fl o Oo Cm no Oc Ns Ar option
164 Set or reset options.
165 .Bl -tag -width indent
166 .It Oo Cm no Oc Ns Cm async
169 backed devices: avoid
171 for increased performance but
172 at the risk of deadlocking the entire kernel.
173 .It Oo Cm no Oc Ns Cm reserve
174 Allocate and reserve all needed storage from the start, rather than as needed.
175 .It Oo Cm no Oc Ns Cm cluster
176 Enable clustering on this disk.
177 .It Oo Cm no Oc Ns Cm compress
178 Enable/Disable compression features to reduce memory usage.
179 .It Oo Cm no Oc Ns Cm force
180 Disable/Enable extra sanity checks to prevent the user from doing something
181 that might adversely affect the system.
182 .It Oo Cm no Oc Ns Cm readonly
183 Enable/Disable readonly mode.
186 Request a specific unit number for the
188 device instead of automatic allocation.
194 is provided for convenience as an abbreviation of
200 To create a 4 megabyte
203 The name of the allocated unit will be output on stdout like
206 .Dl mdconfig -a -t malloc -s 4m
208 To create a disk named
214 .Dl mdconfig -a -t vnode -f /tmp/boot.flp -u 4
216 To detach and free all resources used by
221 To create a 128MByte swap backed disk, initialize an
223 file system on it, and mount it on
225 .Bd -literal -offset indent
226 mdconfig -a -t swap -s 128M -u 10
232 To create a 5MB file-backed disk
237 .Bd -literal -offset indent
238 dd if=/dev/zero of=somebackingfile bs=1k count=5k
239 mdconfig -f somebackingfile -u 0
247 device out of an ISO 9660 CD image file
251 are implied), using the first available
253 device, and then mount the new memory disk:
254 .Bd -literal -offset indent
255 mount -t cd9660 /dev/`mdconfig -f cdimage.iso` /mnt
267 utility first appeared in
269 as a cleaner replacement for the
277 utility was written by
278 .An Poul-Henning Kamp
279 .Aq phk@FreeBSD.org .