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 backingstore for this memory disk.
101 Swap space is used to back this memory disk.
104 Filename to use for the vnode type memory disk.
106 List configured devices.
109 display details about that particular device.
111 When printing md device names, print only the unit number without the
114 Size of the memory disk.
116 is the number of 512 byte sectors unless suffixed with a
121 denotes byte, kilobyte, megabyte, gigabyte and terabyte respectively.
122 .It Fl S Ar sectorsize
123 Sectorsize to use for malloc backed device.
124 .It Fl x Ar sectors/track
125 See the description of the
128 .It Fl y Ar heads/cylinder
137 options can be used to specify a synthetic geometry.
138 This is useful for constructing bootable images for later download to
140 .It Fl o Oo Cm no Oc Ns Ar option
141 Set or reset options.
142 .Bl -tag -width indent
143 .It Oo Cm no Oc Ns Cm async
146 backed devices: avoid
148 for increased performance but
149 at the risk of deadlocking the entire kernel.
150 .It Oo Cm no Oc Ns Cm reserve
151 Allocate and reserve all needed storage from the start, rather than as needed.
152 .It Oo Cm no Oc Ns Cm cluster
153 Enable clustering on this disk.
154 .It Oo Cm no Oc Ns Cm compress
155 Enable/Disable compression features to reduce memory usage.
156 .It Oo Cm no Oc Ns Cm force
157 Disable/Enable extra sanity checks to prevent the user from doing something
158 that might adversely affect the system.
159 .It Oo Cm no Oc Ns Cm readonly
160 Enable/Disable readonly mode.
163 Request a specific unit number for the
165 device instead of automatic allocation.
168 To create a 4 megabyte
171 The name of the allocated unit will be output on stdout like
174 .Dl mdconfig -a -t malloc -s 4m
176 To create a disk named
182 .Dl mdconfig -a -t vnode -f /tmp/boot.flp -u 4
184 To detach and free all resources used by
189 To create and mount a 128MByte swap backed file system on
191 .Bd -literal -offset indent
192 mdconfig -a -t swap -s 128M -u 10
198 To create a 5MB file-backed disk:
199 .Bd -literal -offset indent
200 dd if=/dev/zero of=somebackingfile bs=1k count=5k
201 mdconfig -a -t vnode -f somebackingfile -u 0
215 utility first appeared in
217 as a cleaner replacement for the
225 utility was written by
226 .An Poul-Henning Kamp
227 .Aq phk@FreeBSD.org .