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
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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
70 .Op Fl o Oo Cm no Oc Ns Ar force
81 utility configures and enables
85 Options indicate an action to be performed:
86 .Bl -tag -width indent
89 This will configure and attach a memory disk with the
90 parameters specified and attach it to the system.
92 Detach a memory disk from the system and release all resources.
96 Select the type of the memory disk.
97 .Bl -tag -width "malloc"
99 Storage for this type of memory disk is allocated with
101 This limits the size to the malloc bucket limit in the kernel.
104 option is not set, creating and filling a large
105 malloc-backed memory disk is a very easy way to
108 A file specified with
110 becomes the backing store for this memory disk.
112 Storage for this type of memory disk is allocated from buffer
114 Pages get pushed out to swap when the system is under memory
115 pressure, otherwise they stay in the operating memory.
118 backing is generally preferred instead of using
123 Filename to use for the vnode type memory disk.
128 options are implied if not specified.
130 List configured devices.
133 display details about that particular device.
136 option is specified, show all details.
140 device names, print only the unit number without the
144 Size of the memory disk.
146 is the number of 512 byte sectors unless suffixed with a
151 denotes byte, kilobyte, megabyte, gigabyte and terabyte respectively.
156 options are implied if not specified.
157 .It Fl S Ar sectorsize
158 Sectorsize to use for the memory disk, in bytes.
159 .It Fl x Ar sectors/track
160 See the description of the
163 .It Fl y Ar heads/cylinder
172 options can be used to specify a synthetic geometry.
173 This is useful for constructing bootable images for later download to
175 .It Fl o Oo Cm no Oc Ns Ar option
176 Set or reset options.
177 .Bl -tag -width indent
178 .It Oo Cm no Oc Ns Cm async
181 backed devices: avoid
183 for increased performance but
184 at the risk of deadlocking the entire kernel.
185 .It Oo Cm no Oc Ns Cm reserve
186 Allocate and reserve all needed storage from the start, rather than as needed.
187 .It Oo Cm no Oc Ns Cm cluster
188 Enable clustering on this disk.
189 .It Oo Cm no Oc Ns Cm compress
190 Enable/disable compression features to reduce memory usage.
191 .It Oo Cm no Oc Ns Cm force
192 Disable/enable extra sanity checks to prevent the user from doing something
193 that might adversely affect the system.
194 .It Oo Cm no Oc Ns Cm readonly
195 Enable/disable readonly mode.
198 Request a specific unit number for the
200 device instead of automatic allocation.
206 is provided for convenience as an abbreviation of
215 The name of the allocated unit will be printed on stdout, such as
218 .Dl mdconfig -a -t malloc -s 4m
226 .Dl mdconfig -a -t vnode -f /tmp/boot.flp -u 4
228 Detach and free all resources used by
233 Create a 128MByte swap backed disk, initialize an
235 file system on it, and mount it on
237 .Bd -literal -offset indent
238 mdconfig -a -t swap -s 128M -u 10
244 Create a 5MB file-backed disk
250 .Bd -literal -offset indent
251 dd if=/dev/zero of=somebackingfile bs=1k count=5k
252 mdconfig -f somebackingfile -u 0
260 device out of an ISO 9660 CD image file
265 .Pc , using the first available
267 device, and then mount the new memory disk:
268 .Bd -literal -offset indent
269 mount -t cd9660 /dev/`mdconfig -f cdimage.iso` /mnt
272 Create a file-backed device from a hard disk image that begins
273 with 512K of raw header information.
275 is used to skip over the header information, positioning
277 to the start of the filesystem in the image.
278 .Bd -literal -offset indent
279 mdconfig -f diskimage.img -u 1
280 gnop create -o 512K md1
281 mount /dev/md1.nop /mnt
293 utility first appeared in
295 as a cleaner replacement for the
303 utility was written by
304 .An Poul-Henning Kamp
305 .Aq phk@FreeBSD.org .