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37 .\" @(#)vnconfig.8 8.1 (Berkeley) 6/5/93
38 .\" $FreeBSD: src/usr.sbin/vnconfig/vnconfig.8,v 1.14.2.8 2003/01/04 22:35:53 keramida Exp $
45 .Nd configure and enable vnode disks
50 .Op , Ns Ar option Ns Ar ... Oc
52 .Op , Ns Ar option Ns Ar ... Oc
54 .Ar special_file Op Ar regular_file
61 .Op Fl f Ar config_file
65 command configures and enables vnode pseudo disk devices.
66 The first form of the command will associate the special file
70 allowing the latter to be accessed as though it were a disk.
71 Hence a regular file within the filesystem can be used for swapping
72 or can contain a filesystem that is mounted in the name space. If you
73 want to use swap backing store for your device instead of a file, you
74 can leave regular_file out and specify the size of the block device
77 Options indicate an action to be performed:
78 .Bl -tag -width indent
80 Read a command file and performs the
81 specified actions for each device/file pair.
84 If successful, references to
86 will access the contents of
89 Disable (if possible) the specified feature.
91 Configure the device and enables any
94 If no feature was specified,
98 .It Fl f Ar config_file
101 as an alternate config file.
103 Fiddle global options.
107 The list of allowed flags and their meanings are:
108 .Bl -tag -width "follow"
110 use disk/slice labels.
112 Pre-reserve the blocks underlying the file or swap backing store. Currently only
113 works for swap backing store. This option also disables on-the-fly freeing of
114 the underlying backing store (for example, when you remove a large file).
115 Use this option if you wish to avoid long-term fragmentation of the backing
116 store. Also note that when this option is used, the initial contents of the
117 backing store may contain garbage rather then zeros. It may even be possible to
118 recover the prior contents of a swap-backed VN across a reboot if the VN device
119 is configured before any swap is allocated by the system.
140 The list of allowed flags and their meanings are the same as for the
150 If no regular file is specified, VN will use swap for backing store.
151 This option specifies the size of the device. For example, '23m' for
152 23 megabytes. The VN device will round the size up to a machine page boundary.
153 Filesystems up to 7.9 terabytes are supported. When specified along with
154 a regular file, this option overrides the regular file's size insofar as
157 When a regular file is specified, VN will ftruncate() the file to 0 first.
158 Normally you should also specify the -S option to set the size of the file.
159 This option also creates the file if it did not previously exist.
160 This option is only meaningful if the -S option has been specified.
162 When a regular file is specified, VN will zero the contents of the file to
163 ensure that all blocks have been allocated by the filesystem. This option is
164 only meaningful if the -S option has been specified.
166 Disable and ``unconfigure'' the device.
168 Print messages to stdout describing actions taken.
171 If no action option is given,
177 argument specifies a feature that can be enabled via the
180 .Bl -tag -width indent
182 Swapping is enabled on the special file.
185 .It Dv mountro Ns = Ns Pa mount_point
186 The special file is mounted read-only on
190 .It Dv mountrw Ns = Ns Pa mount_point
191 The special file is mounted read-write on
195 .It Dv mount Ns = Ns Pa mount_point
196 Same as ``mountrw=''.
199 A configuration file contains one line per device/file pair in the form:
201 special_file regular_file [ feature ]
204 where fields are separated by white space.
205 The previously described action options serve to configure, enable,
206 disable or unconfigure all devices in the configuration file.
208 .Bl -tag -width /etc/vntab -compact
210 default configuration file for
216 .Dl vnconfig vn0c /tmp/diskimage
218 Configures the vnode disk
221 .Dl vnconfig -e vn0c /var/swapfile swap
225 and enables swapping on it.
227 .Dl vnconfig -c -v /dev/vn0 cdimage.iso
228 .Dl mount -t cd9660 -o ro /dev/vn0 /mnt
230 Mount an ISO9660 CD image file.
235 Unmount the CD image file.
237 .Dl vnconfig -d vn0c myfilesystem mount=/mnt
244 Configures and enables all devices specified in
247 .Dl vnconfig -s labels -c vn0 somebackingfile
248 .Dl disklabel -r -w vn0 auto
251 Is an example of how to configure a file-backed VN disk with a disk label
252 and to initialize and then edit the label. Once you create the label, you
253 can partition your VN disk and, for example, create a filesystem on one of
254 the partitions. If you are using a file as backing store, it may be possible
255 to recover your VN disk after a crash by vnconfig'ing the same file again
256 and using the VN configuration already stored in the file rather then
257 relabeling and recreating the filesystem. It is even possible to fsck the
258 VN partitions that previously contained filesystems.
260 .Dl vnconfig -e -s labels,reserve -S 400m vn1
261 .Dl disklabel -r -w vn1 auto
263 .Dl mount /dev/vn1c /usr/obj
265 Is an example of a swap-backed VN disk configuration. This example assumes
266 that you have at least 400 megabytes of swap free (and hopefully much more).
267 The swap space is pre-reserved in order to maintain maximum performance.
268 We then label the disk, newfs it, and mount it as /usr/obj. Swap-backed VN
269 devices are recoverable after a crash if you (A) use the reserve flag, and if
270 (B) the same swap is reserved as was the last time, meaning that such
271 vnconfig's would have to be run in your rc.local. In general, though, you
272 only use swap-backed VN devices to hold information you don't mind losing