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 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 readonly
250 Enable/disable readonly mode.
251 .It Oo Cm no Oc Ns Cm verify
254 backed devices: enable/disable requesting verification of the
255 file used for backing store.
256 The type of verification depends on which security features are available.
257 One example of verification is testing file integrity with
258 checksums or cryptographic signatures.
261 Request a specific unit number or device name for the
263 device instead of automatic allocation.
264 If a device name is specified, it must be start with
266 followed by the unit number.
272 is provided for convenience as an abbreviation of
281 The name of the allocated unit will be printed on stdout, such as
283 .Bd -literal -offset indent
284 mdconfig /tmp/boot.flp
287 Create a 1 gigabyte swap backed memory disk named
289 .Bd -literal -offset indent
290 mdconfig -s 1g -u md3
293 Detach and free all resources used by
295 .Bd -literal -offset indent
299 Show detailed information on current memory disks:
300 .Bd -literal -offset indent
306 memory disk to 2 gigabytes:
307 .Bd -literal -offset indent
308 mdconfig -rs 2g -u md3
311 Create a 1 gigabyte swap backed disk, initialize an
313 file system on it, and mount it on
315 .Bd -literal -offset indent
316 mdconfig -s 1g -u md10
322 Create a memory disk out of an ISO 9660 CD image file,
323 using the first available
325 device, and then mount it:
326 .Bd -literal -offset indent
327 mount -t cd9660 /dev/`mdconfig -f cdimage.iso` /mnt
330 Create a file-backed device from a hard disk image that begins
331 with 512K of raw header information.
333 is used to skip over the header information, positioning
335 to the start of the filesystem in the image.
336 .Bd -literal -offset indent
337 mdconfig -u md1 -f diskimage.img
338 gnop create -o 512K md1
339 mount /dev/md1.nop /mnt
351 utility first appeared in
353 as a cleaner replacement for the
361 utility was written by
362 .An Poul-Henning Kamp Aq Mt phk@FreeBSD.org .