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 create and control 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
82 utility creates and controls
86 Options indicate an action to be performed:
87 .Bl -tag -width indent
90 This will configure and attach a memory disk with the
91 parameters specified and attach it to the system.
94 option is not provided, the newly created device name will be printed on stdout.
96 Detach a memory disk from the system and release all resources.
100 Select the type of the memory disk.
101 .Bl -tag -width "malloc"
103 Storage for this type of memory disk is allocated with
105 This limits the size to the malloc bucket limit in the kernel.
108 option is not set, creating and filling a large
109 malloc-backed memory disk is a very easy way to
112 A file specified with
114 becomes the backing store for this memory disk.
116 Storage for this type of memory disk is allocated from buffer
118 Pages get pushed out to swap when the system is under memory
119 pressure, otherwise they stay in the operating memory.
122 backing is generally preferred instead of using
126 Bitsink; all writes do nothing, all reads return zeroes.
129 Filename to use for the vnode type memory disk.
134 options are implied if not specified.
136 List configured devices.
139 display details about that particular device.
144 device names of which
146 is used as the backing store.
151 options are specified,
152 display devices which match the two conditions.
155 option is specified, show all details.
159 device names, print only the unit number without the
163 Size of the memory disk.
165 is the number of 512 byte sectors unless suffixed with a
166 .Cm b , k , m , g , t ,
170 denotes byte, kilobyte, megabyte, gigabyte, terabyte and petabyte respectively.
171 When used without the
177 options are implied if not specified.
178 .It Fl S Ar sectorsize
179 Sectorsize to use for the memory disk, in bytes.
180 .It Fl x Ar sectors/track
181 See the description of the
184 .It Fl y Ar heads/cylinder
193 options can be used to specify a synthetic geometry.
194 This is useful for constructing bootable images for later download to
196 .It Fl o Oo Cm no Oc Ns Ar option
197 Set or reset options.
198 .Bl -tag -width indent
199 .It Oo Cm no Oc Ns Cm async
202 backed devices: avoid
204 for increased performance but
205 at the risk of deadlocking the entire kernel.
206 .It Oo Cm no Oc Ns Cm reserve
207 Allocate and reserve all needed storage from the start, rather than as needed.
208 .It Oo Cm no Oc Ns Cm cluster
209 Enable clustering on this disk.
210 .It Oo Cm no Oc Ns Cm compress
211 Enable/disable compression features to reduce memory usage.
212 .It Oo Cm no Oc Ns Cm force
213 Disable/enable extra sanity checks to prevent the user from doing something
214 that might adversely affect the system.
215 This can be used with the
217 flag to forcibly destroy an
219 disk that is still in use.
220 .It Oo Cm no Oc Ns Cm readonly
221 Enable/disable readonly mode.
224 Request a specific unit number or device name for the
226 device instead of automatic allocation.
227 If a device name is specified, it must be start with
229 followed by the unit number.
235 is provided for convenience as an abbreviation of
244 The name of the allocated unit will be printed on stdout, such as
246 .Bd -literal -offset indent
247 mdconfig /tmp/boot.flp
250 Create a 1 gigabyte swap backed memory disk named
252 .Bd -literal -offset indent
253 mdconfig -s 1g -u md3
256 Detach and free all resources used by
258 .Bd -literal -offset indent
262 Show detailed information on current memory disks:
263 .Bd -literal -offset indent
269 memory disk to 2 gigabytes:
270 .Bd -literal -offset indent
271 mdconfig -rs 2g -u md3
274 Create a 1 gigabyte swap backed disk, initialize an
276 file system on it, and mount it on
278 .Bd -literal -offset indent
279 mdconfig -s 1g -u md10
285 Create a memory disk out of an ISO 9660 CD image file,
286 using the first available
288 device, and then mount it:
289 .Bd -literal -offset indent
290 mount -t cd9660 /dev/`mdconfig -f cdimage.iso` /mnt
293 Create a file-backed device from a hard disk image that begins
294 with 512K of raw header information.
296 is used to skip over the header information, positioning
298 to the start of the filesystem in the image.
299 .Bd -literal -offset indent
300 mdconfig -u md1 -f diskimage.img
301 gnop create -o 512K md1
302 mount /dev/md1.nop /mnt
313 utility first appeared in
315 as a cleaner replacement for the
323 utility was written by
324 .An Poul-Henning Kamp Aq Mt phk@FreeBSD.org .