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33 .\" @(#)vnconfig.8 8.1 (Berkeley) 6/5/93
34 .\" $FreeBSD: src/usr.sbin/vnconfig/vnconfig.8,v 1.14.2.8 2003/01/04 22:35:53 keramida Exp $
35 .\" $DragonFly: src/usr.sbin/vnconfig/vnconfig.8,v 1.10 2008/07/27 22:36:01 thomas Exp $
37 .Dd September 28, 2009
42 .Nd configure and enable vnode disks
49 .Ar special_file Op Ar regular_file
56 .Op Fl f Ar config_file
59 .Op Ar special_file Ar ...
63 command configures, enables and lists vnode pseudo disk devices.
64 The first form of the command will associate the special file
68 allowing the latter to be accessed as though it were a disk.
69 Hence a regular file within the filesystem can be used for swapping
70 or can contain a filesystem that is mounted in the name space.
71 If you want to use swap backing store for your device instead of a file,
74 out and specify the size of the block device
79 Options indicate an action to be performed:
80 .Bl -tag -width indent
82 Read a command file and performs the
83 specified actions for each device/file pair.
86 If successful, references to
88 will access the contents of
93 device is autocloned if
97 the name of the resulting device is printed on stdout.
99 Disable (if possible) the specified feature.
101 Configure the device and enables any
104 If no feature was specified,
108 .It Fl f Ar config_file
109 Specify configuration file.
113 Fiddle global options.
114 .It Fl l Ar special_file Ar ...
117 devices and indicate which ones are in use.
120 list is given, only those devices will be described.
124 which is a comma separated string of options.
125 The list of allowed options and their meanings are:
126 .Bl -tag -width "reserve"
128 Pre-reserve the blocks underlying the file or swap backing store.
129 Currently only works for swap backing store.
130 This option also disables on-the-fly freeing of
131 the underlying backing store (for example, when you remove a large file).
132 Use this option if you wish to avoid long-term fragmentation of the backing
134 Also note that when this option is used, the initial contents of the
135 backing store may contain garbage rather than zeros.
136 It may even be possible to
137 recover the prior contents of a swap-backed
139 across a reboot if the
142 is configured before any swap is allocated by the system.
160 Turn off all options.
165 which is a comma separated string of options.
166 The list of allowed options and their meanings are the same as for the
172 .Brq Cm k , m , g , t
175 If no regular file is specified,
177 will use swap for backing store.
178 This option specifies the size of the device.
183 In the absence of a size modifier,
188 device will round the size up to a machine page boundary.
189 Filesystems up to 7.9 terabytes are supported.
190 When specified along with
191 a regular file, this option overrides the regular file's size insofar as
195 When a regular file is specified,
199 the file to length 0 first.
200 Normally you should also specify the
202 option to set the size of the file.
203 This option also creates the file if it did not previously exist.
204 This option is only meaningful if the
206 option has been specified.
208 When a regular file is specified,
210 will zero the contents of the file to
211 ensure that all blocks have been allocated by the filesystem.
212 This option is only meaningful if the
214 option has been specified.
216 Disable and ``unconfigure'' the device.
218 Print messages to stdout describing actions taken.
221 If no action option is given,
227 argument specifies a feature that can be enabled via the
230 .Bl -tag -width indent
232 Swapping is enabled on the special file.
235 .It Cm mountro= Ns Ar mount_point
236 The special file is mounted read-only on
240 .It Cm mountrw= Ns Ar mount_point
241 The special file is mounted read-write on
245 .It Cm mount= Ns Ar mount_point
247 .Cm mountrw= Ns Ar mount_point .
250 A configuration file contains one line per device/file pair in the form:
252 special_file regular_file [feature]
255 where fields are separated by white space.
256 The previously described action options serve to configure, enable,
257 disable or unconfigure all devices in the configuration file.
259 .Bl -tag -width /etc/vntab -compact
261 default configuration file for
266 .Dl vnconfig vn /tmp/diskimage
268 Configures an autocloned vnode disk,
269 the name of the resulting device is printed, e.g.\&
272 .Dl vnconfig vn0 /tmp/diskimage
274 Configures the vnode disk
277 .Dl vnconfig -e vn0 /var/swapfile swap
281 and enables swapping on it.
283 .Dl vnconfig -c -v /dev/vn0 cdimage.iso
284 .Dl mount -t cd9660 -o ro /dev/vn0 /mnt
286 Mount an ISO9660 CD image file.
291 Unmount the CD image file.
293 .Dl vnconfig -d vn0 myfilesystem mount=/mnt
300 Configures and enables all devices specified in
303 .Dl vnconfig -c vn0 somebackingfile
304 .Dl disklabel -r -w vn0s0 auto
305 .Dl disklabel -e vn0s0
307 Is an example of how to configure a file-backed
309 disk with a disk label
310 and to initialize and then edit the label.
311 Once you create the label, you
314 disk and, for example, create a filesystem on one of the partitions.
315 If you are using a file as backing store, it may be possible
318 disk after a crash by
320 the same file again and using the
322 configuration already stored in the file rather than
323 relabeling and recreating the filesystem.
324 It is even possible to
328 partitions that previously contained filesystems.
330 .Dl vnconfig -e -s reserve -S 400m vn1
331 .Dl disklabel -r -w vn1s0 auto
333 .Dl mount /dev/vn1s0 /usr/obj
335 Is an example of a swap-backed
339 that you have at least 400 megabytes of swap free (and hopefully much more).
340 The swap space is pre-reserved in order to maintain maximum performance.
341 We then label the disk, newfs it, and mount it as
345 devices are recoverable after a crash if you (A) use the
348 (B) the same swap is reserved as was the last time, meaning that such
350 would have to be run in your
352 In general, though, you only use swap-backed
354 devices to hold information you don't mind losing on every reboot.