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
62 .Op Fl o Oo Cm no Oc Ns Ar force
67 .Op Fl o Oo Cm no Oc Ns Ar force
79 utility creates and controls
83 Options indicate an action to be performed:
84 .Bl -tag -width indent
87 This will configure and attach a memory disk with the
88 parameters specified and attach it to the system.
91 option is not provided, the newly created device name will be printed on stdout.
93 Detach a memory disk from the system and release all resources.
97 Select the type of the memory disk.
98 .Bl -tag -width "malloc"
100 Storage for this type of memory disk is allocated with
102 This limits the size to the malloc bucket limit in the kernel.
105 option is not set, creating and filling a large
106 malloc-backed memory disk is a very easy way to
109 A file specified with
111 becomes the backing store for this memory disk.
113 Storage for this type of memory disk is allocated from buffer
115 Pages get pushed out to swap when the system is under memory
116 pressure, otherwise they stay in the operating memory.
119 backing is generally preferred instead of using
123 Bitsink; all writes do nothing, all reads return zeroes.
126 Filename to use for the vnode type memory disk.
131 options are implied if not specified.
133 List configured devices.
136 display details about that particular device.
141 device names of which
143 is used as the backing store.
148 options are specified,
149 display devices which match the two conditions.
152 option is specified, show all details.
156 device names, print only the unit number without the
160 Size of the memory disk.
162 is the number of 512 byte sectors unless suffixed with a
163 .Cm b , k , m , g , t ,
167 denotes byte, kilobyte, megabyte, gigabyte, terabyte and petabyte respectively.
168 When used without the
174 options are implied if not specified.
175 .It Fl S Ar sectorsize
176 Sectorsize to use for the memory disk, in bytes.
177 .It Fl x Ar sectors/track
178 See the description of the
181 .It Fl y Ar heads/cylinder
190 options can be used to specify a synthetic geometry.
191 This is useful for constructing bootable images for later download to
194 Associate a label (arbitrary string) with the new memory disk.
195 The label can then be inspected with
196 .Bd -literal -offset indent
199 .It Fl o Oo Cm no Oc Ns Ar option
200 Set or reset options.
201 .Bl -tag -width indent
202 .It Oo Cm no Oc Ns Cm async
205 backed devices: avoid
207 for increased performance but
208 at the risk of deadlocking the entire kernel.
209 .It Oo Cm no Oc Ns Cm reserve
210 Allocate and reserve all needed storage from the start, rather than as needed.
211 .It Oo Cm no Oc Ns Cm cluster
212 Enable clustering on this disk.
213 .It Oo Cm no Oc Ns Cm compress
214 Enable/disable compression features to reduce memory usage.
215 .It Oo Cm no Oc Ns Cm force
216 Disable/enable extra sanity checks to prevent the user from doing something
217 that might adversely affect the system.
218 This can be used with the
220 flag to forcibly destroy an
222 disk that is still in use.
223 .It Oo Cm no Oc Ns Cm readonly
224 Enable/disable readonly mode.
225 .It Oo Cm no Oc Ns Cm verify
228 backed devices: enable/disable requesting verification of the
229 file used for backing store.
230 The type of verification depends on which security features are available.
231 One example of verification is testing file integrity with
232 checksums or cryptographic signatures.
235 Request a specific unit number or device name for the
237 device instead of automatic allocation.
238 If a device name is specified, it must be start with
240 followed by the unit number.
246 is provided for convenience as an abbreviation of
255 The name of the allocated unit will be printed on stdout, such as
257 .Bd -literal -offset indent
258 mdconfig /tmp/boot.flp
261 Create a 1 gigabyte swap backed memory disk named
263 .Bd -literal -offset indent
264 mdconfig -s 1g -u md3
267 Detach and free all resources used by
269 .Bd -literal -offset indent
273 Show detailed information on current memory disks:
274 .Bd -literal -offset indent
280 memory disk to 2 gigabytes:
281 .Bd -literal -offset indent
282 mdconfig -rs 2g -u md3
285 Create a 1 gigabyte swap backed disk, initialize an
287 file system on it, and mount it on
289 .Bd -literal -offset indent
290 mdconfig -s 1g -u md10
296 Create a memory disk out of an ISO 9660 CD image file,
297 using the first available
299 device, and then mount it:
300 .Bd -literal -offset indent
301 mount -t cd9660 /dev/`mdconfig -f cdimage.iso` /mnt
304 Create a file-backed device from a hard disk image that begins
305 with 512K of raw header information.
307 is used to skip over the header information, positioning
309 to the start of the filesystem in the image.
310 .Bd -literal -offset indent
311 mdconfig -u md1 -f diskimage.img
312 gnop create -o 512K md1
313 mount /dev/md1.nop /mnt
325 utility first appeared in
327 as a cleaner replacement for the
335 utility was written by
336 .An Poul-Henning Kamp Aq Mt phk@FreeBSD.org .