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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35 .\" @(#)vnconfig.8 8.1 (Berkeley) 6/5/93
36 .\" from: src/usr.sbin/vnconfig/vnconfig.8,v 1.19 2000/12/27 15:30:29
45 .Nd create and control memory disks
51 .Oo Fl o Oo Cm no Oc Ns Ar option Oc ...
54 .Op Fl S Ar sectorsize
56 .Op Fl x Ar sectors/track
57 .Op Fl y Ar heads/cylinder
61 .Op Fl o Oo Cm no Oc Ns Ar force
66 .Op Fl o Oo Cm no Oc Ns Ar force
78 utility creates and controls
82 Options indicate an action to be performed:
83 .Bl -tag -width indent
86 This will configure and attach a memory disk with the
87 parameters specified and attach it to the system.
90 option is not provided, the newly created device name will be printed on stdout.
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
122 Bitsink; all writes do nothing, all reads return zeroes.
125 Filename to use for the vnode type memory disk.
130 options are implied if not specified.
132 List configured devices.
135 display details about that particular device.
140 device names of which
142 is used as the backing store.
147 options are specified,
148 display devices which match the two conditions.
151 option is specified, show all details.
155 device names, print only the unit number without the
159 Size of the memory disk.
161 is the number of 512 byte sectors unless suffixed with a
162 .Cm b , k , m , g , t ,
166 denotes byte, kilobyte, megabyte, gigabyte, terabyte and petabyte respectively.
167 When used without the
173 options are implied if not specified.
174 .It Fl S Ar sectorsize
175 Sectorsize to use for the memory disk, in bytes.
176 .It Fl x Ar sectors/track
177 See the description of the
180 .It Fl y Ar heads/cylinder
189 options can be used to specify a synthetic geometry.
190 This is useful for constructing bootable images for later download to
192 .It Fl o Oo Cm no Oc Ns Ar option
193 Set or reset options.
194 .Bl -tag -width indent
195 .It Oo Cm no Oc Ns Cm async
198 backed devices: avoid
200 for increased performance but
201 at the risk of deadlocking the entire kernel.
202 .It Oo Cm no Oc Ns Cm reserve
203 Allocate and reserve all needed storage from the start, rather than as needed.
204 .It Oo Cm no Oc Ns Cm cluster
205 Enable clustering on this disk.
206 .It Oo Cm no Oc Ns Cm compress
207 Enable/disable compression features to reduce memory usage.
208 .It Oo Cm no Oc Ns Cm force
209 Disable/enable extra sanity checks to prevent the user from doing something
210 that might adversely affect the system.
211 This can be used with the
213 flag to forcibly destroy an
215 disk that is still in use.
216 .It Oo Cm no Oc Ns Cm readonly
217 Enable/disable readonly mode.
220 Request a specific unit number or device name for the
222 device instead of automatic allocation.
223 If a device name is specified, it must be start with
225 followed by the unit number.
231 is provided for convenience as an abbreviation of
240 The name of the allocated unit will be printed on stdout, such as
242 .Bd -literal -offset indent
243 mdconfig /tmp/boot.flp
246 Create a 1 gigabyte swap backed memory disk named
248 .Bd -literal -offset indent
249 mdconfig -s 1g -u md3
252 Detach and free all resources used by
254 .Bd -literal -offset indent
258 Show detailed information on current memory disks:
259 .Bd -literal -offset indent
265 memory disk to 2 gigabytes:
266 .Bd -literal -offset indent
267 mdconfig -rs 2g -u md3
270 Create a 1 gigabyte swap backed disk, initialize an
272 file system on it, and mount it on
274 .Bd -literal -offset indent
275 mdconfig -s 1g -u md10
281 Create a memory disk out of an ISO 9660 CD image file,
282 using the first available
284 device, and then mount it:
285 .Bd -literal -offset indent
286 mount -t cd9660 /dev/`mdconfig -f cdimage.iso` /mnt
289 Create a file-backed device from a hard disk image that begins
290 with 512K of raw header information.
292 is used to skip over the header information, positioning
294 to the start of the filesystem in the image.
295 .Bd -literal -offset indent
296 mdconfig -u md1 -f diskimage.img
297 gnop create -o 512K md1
298 mount /dev/md1.nop /mnt
309 utility first appeared in
311 as a cleaner replacement for the
319 utility was written by
320 .An Poul-Henning Kamp Aq Mt phk@FreeBSD.org .