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.
11 .\" Redistribution and use in source and binary forms, with or without
12 .\" modification, are permitted provided that the following conditions
14 .\" 1. Redistributions of source code must retain the above copyright
15 .\" notice, this list of conditions and the following disclaimer.
16 .\" 2. Redistributions in binary form must reproduce the above copyright
17 .\" notice, this list of conditions and the following disclaimer in the
18 .\" documentation and/or other materials provided with the distribution.
19 .\" 3. Neither the name of the University nor the names of its contributors
20 .\" may be used to endorse or promote products derived from this software
21 .\" without specific prior written permission.
23 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 cache
212 backed devices: enable/disable caching of data in system caches.
213 The default is to not cache.
215 Accesses via the device are converted to accesses via the vnode.
216 The caching policy for the vnode is used initially.
217 This is normally to cache.
218 This caching policy is retained if the
221 Otherwise, caching is limited
222 by releasing data from caches soon after each access.
223 The release has the same semantics as the
224 .Dv POSIX_FADV_DONTNEED
226 .Xr posix_fadvise 2 .
227 The result is that with normal (non-zfs) caching,
228 buffers are released from the buffer cache soon after they are constructed,
229 but their data is kept in the page cache at lower priority.
233 option tends to waste memory by giving unwanted double caching,
234 but it saves time if there is memory to spare.
235 .It Oo Cm no Oc Ns Cm reserve
236 Allocate and reserve all needed storage from the start, rather than as needed.
237 .It Oo Cm no Oc Ns Cm cluster
238 Enable clustering on this disk.
239 .It Oo Cm no Oc Ns Cm compress
240 Enable/disable compression features to reduce memory usage.
241 .It Oo Cm no Oc Ns Cm force
242 Disable/enable extra sanity checks to prevent the user from doing something
243 that might adversely affect the system.
244 This can be used with the
246 flag to forcibly destroy an
248 disk that is still in use.
249 .It Oo Cm no Oc Ns Cm mustdealloc
252 backed devices: detect whether hole-punching is supported by the underlying file
254 If the file system supports hole-punching, then to handle a
256 request, some or all of the request's operation range may be turned into a hole
257 in the file used for backing store.
258 Any parts which are not turned into holes are zero-filled in
260 If the file system does not support
263 requests to the device are not handled and will fail with
269 .Oo Cm no Oc Ns Cm mustdealloc
272 request, if the file system supports hole-punching, some or all of the request's
273 operation range may be turned into a hole in the file used for backing store.
274 Any parts which are not turned into holes are zero-filled in the file.
275 If the file system of the vnode type memory disk does not support hole-punching,
276 the request's operation range is zero-filled in the file.
277 .It Oo Cm no Oc Ns Cm readonly
278 Enable/disable readonly mode.
279 .It Oo Cm no Oc Ns Cm verify
282 backed devices: enable/disable requesting verification of the
283 file used for backing store.
284 The type of verification depends on which security features are available.
285 One example of verification is testing file integrity with
286 checksums or cryptographic signatures.
289 Request a specific unit number or device name for the
291 device instead of automatic allocation.
292 If a device name is specified, it must start with
294 followed by the unit number.
300 is provided for convenience as an abbreviation of
309 The name of the allocated unit will be printed on stdout, such as
311 .Bd -literal -offset indent
312 mdconfig /tmp/boot.flp
315 Create a 1 gigabyte swap backed memory disk named
317 .Bd -literal -offset indent
318 mdconfig -s 1g -u md3
321 Detach and free all resources used by
323 .Bd -literal -offset indent
327 Show detailed information on current memory disks:
328 .Bd -literal -offset indent
334 memory disk to 2 gigabytes:
335 .Bd -literal -offset indent
336 mdconfig -rs 2g -u md3
339 Create a 1 gigabyte swap backed disk, initialize an
341 file system on it, and mount it on
343 .Bd -literal -offset indent
344 mdconfig -s 1g -u md10
350 Create a memory disk out of an ISO 9660 CD image file,
351 using the first available
353 device, and then mount it:
354 .Bd -literal -offset indent
355 mount -t cd9660 /dev/`mdconfig -f cdimage.iso` /mnt
358 Create a file-backed device from a hard disk image that begins
359 with 512K of raw header information.
361 is used to skip over the header information, positioning
363 to the start of the filesystem in the image.
364 .Bd -literal -offset indent
365 mdconfig -u md1 -f diskimage.img
366 gnop create -o 512K md1
367 mount /dev/md1.nop /mnt
382 utility first appeared in
384 as a cleaner replacement for the vn kernel module
385 and the vnconfig utility combo.
389 utility was written by
390 .An Poul-Henning Kamp Aq Mt phk@FreeBSD.org .