vn.4: Describe autocloning & use standard description for kernel modules
[dragonfly.git] / usr.sbin / vnconfig / vnconfig.8
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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 $
daa51328 39.\" $DragonFly: src/usr.sbin/vnconfig/vnconfig.8,v 1.10 2008/07/27 22:36:01 thomas Exp $
984263bc 40.\"
8d6b0489 41.Dd January 30, 2008
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42.Dt VNCONFIG 8
43.Os
44.Sh NAME
45.Nm vnconfig
46.Nd configure and enable vnode disks
47.Sh SYNOPSIS
48.Nm
49.Op Fl cdeguvTZ
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50.Op Fl s Ar options
51.Op Fl r Ar options
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52.Op Fl S Ar value
53.Ar special_file Op Ar regular_file
54.Op Ar feature
55.Nm
56.Fl a
57.Op Fl cdeguv
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58.Op Fl s Ar options
59.Op Fl r Ar options
984263bc 60.Op Fl f Ar config_file
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61.Nm
62.Fl l
63.Op Ar special_file Ar ...
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64.Sh DESCRIPTION
65The
66.Nm
30c1fde0 67command configures, enables and lists vnode pseudo disk devices.
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68The first form of the command will associate the special file
69.Ar special_file
70with the regular file
71.Ar regular_file
72allowing the latter to be accessed as though it were a disk.
73Hence a regular file within the filesystem can be used for swapping
74or can contain a filesystem that is mounted in the name space. If you
75want to use swap backing store for your device instead of a file, you
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76can leave
77.Ar regular_file
78out and specify the size of the block device
d2469606 79with the
c0ae5e43 80.Fl S
d2469606 81option.
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82.Pp
83Options indicate an action to be performed:
84.Bl -tag -width indent
85.It Fl a
86Read a command file and performs the
87specified actions for each device/file pair.
88.It Fl c
89Configure the device.
90If successful, references to
91.Ar special_file
92will access the contents of
93.Ar regular_file .
94.It Fl d
95Disable (if possible) the specified feature.
96.It Fl e
97Configure the device and enables any
98.Ar feature
99that was specified.
100If no feature was specified,
101.Fl e
102is the same as
103.Fl c .
104.It Fl f Ar config_file
105Use
106.Ar config_file
107as an alternate config file.
108.It Fl g
109Fiddle global options.
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110.It Fl l Ar special_file Ar ...
111List the VN devices and indicate which ones are in use.
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112If a
113.Ar special_file
114list is given, only those devices will be described.
daa51328 115.It Fl r Ar options
984263bc 116Reset
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117.Ar options ,
118which is a comma separated string of options.
119The list of allowed options and their meanings are:
984263bc 120.Bl -tag -width "follow"
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121.It Ar reserve
122Pre-reserve the blocks underlying the file or swap backing store. Currently only
123works for swap backing store. This option also disables on-the-fly freeing of
124the underlying backing store (for example, when you remove a large file).
125Use this option if you wish to avoid long-term fragmentation of the backing
126store. Also note that when this option is used, the initial contents of the
23265324 127backing store may contain garbage rather than zeros. It may even be possible to
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128recover the prior contents of a swap-backed VN across a reboot if the VN device
129is configured before any swap is allocated by the system.
130.It Ar follow
131debug flow in the
132.Xr vn 4
133driver.
134.It Ar debug
135debug data in the
136.Xr vn 4
137driver.
138.It Ar io
139debug I/O in the
140.Xr vn 4
141driver.
142.It Ar all
daa51328 143turn on all options.
984263bc 144.It Ar none
daa51328 145turn off all options.
984263bc 146.El
daa51328 147.It Fl s Ar options
984263bc 148Set
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149.Ar options ,
150which is a comma separated string of options.
151The list of allowed options and their meanings are the same as for the
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152.Fl r
153option.
154.It Fl S Xo
155.Sm off
156.Ar value
157.Es \&{ \&}
158.En Cm k , m , g , t
159.Sm on
160.Xc
161If no regular file is specified, VN will use swap for backing store.
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162This option specifies the size of the device. For example,
163.Sq 23m
164for
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16523 megabytes.
166In the absence of a size modifier,
167.Cm m
168is implied.
169The VN device will round the size up to a machine page boundary.
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170Filesystems up to 7.9 terabytes are supported. When specified along with
171a regular file, this option overrides the regular file's size insofar as
172VN is concerned.
173.It Fl T
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174When a regular file is specified, VN will
175.Fn ftruncate
176the file to length 0 first.
d2469606 177Normally you should also specify the
c0ae5e43 178.Fl S
d2469606 179option to set the size of the file.
984263bc 180This option also creates the file if it did not previously exist.
d2469606 181This option is only meaningful if the
c0ae5e43 182.Fl S
d2469606 183option has been specified.
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184.It Fl Z
185When a regular file is specified, VN will zero the contents of the file to
186ensure that all blocks have been allocated by the filesystem. This option is
d2469606 187only meaningful if the
c0ae5e43 188.Fl S
d2469606 189option has been specified.
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190.It Fl u
191Disable and ``unconfigure'' the device.
192.It Fl v
193Print messages to stdout describing actions taken.
194.El
195.Pp
196If no action option is given,
197.Fl c
198is assumed.
199.Pp
200The
201.Ar feature
202argument specifies a feature that can be enabled via the
203.Fl e
204option:
205.Bl -tag -width indent
206.It Dv swap
207Swapping is enabled on the special file.
208See
209.Xr swapon 2 .
210.It Dv mountro Ns = Ns Pa mount_point
211The special file is mounted read-only on
212.Ar mount_point .
213See
214.Xr mount 2 .
215.It Dv mountrw Ns = Ns Pa mount_point
216The special file is mounted read-write on
217.Ar mount_point .
218See
219.Xr mount 2 .
220.It Dv mount Ns = Ns Pa mount_point
221Same as ``mountrw=''.
222.El
223.Pp
224A configuration file contains one line per device/file pair in the form:
225.Bd -literal
226 special_file regular_file [ feature ]
227.Ed
228.Pp
229where fields are separated by white space.
230The previously described action options serve to configure, enable,
231disable or unconfigure all devices in the configuration file.
232.Sh FILES
233.Bl -tag -width /etc/vntab -compact
234.It Pa /etc/vntab
235default configuration file for
236.Fl a
237option
238.El
239.Sh EXAMPLES
f5ba7fbd 240.Dl vnconfig vn0 /tmp/diskimage
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241.Pp
242Configures the vnode disk
f5ba7fbd 243.Pa vn0 .
984263bc 244.Pp
f5ba7fbd 245.Dl vnconfig -e vn0 /var/swapfile swap
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246.Pp
247Configures
f5ba7fbd 248.Pa vn0
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249and enables swapping on it.
250.Pp
251.Dl vnconfig -c -v /dev/vn0 cdimage.iso
252.Dl mount -t cd9660 -o ro /dev/vn0 /mnt
253.Pp
254Mount an ISO9660 CD image file.
255.Pp
256.Dl umount /mnt
f5ba7fbd 257.Dl vnconfig -u vn0
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258.Pp
259Unmount the CD image file.
260.Pp
f5ba7fbd 261.Dl vnconfig -d vn0 myfilesystem mount=/mnt
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262.Pp
263Unmounts (disables)
f5ba7fbd 264.Pa vn0 .
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265.Pp
266.Dl vnconfig -ae
267.Pp
268Configures and enables all devices specified in
269.Pa /etc/vntab .
270.Pp
45e80934 271.Dl vnconfig -c vn0 somebackingfile
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272.Dl disklabel -r -w vn0s0 auto
273.Dl disklabel -e vn0s0
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274.Pp
275Is an example of how to configure a file-backed VN disk with a disk label
276and to initialize and then edit the label. Once you create the label, you
277can partition your VN disk and, for example, create a filesystem on one of
278the partitions. If you are using a file as backing store, it may be possible
279to recover your VN disk after a crash by vnconfig'ing the same file again
23265324 280and using the VN configuration already stored in the file rather than
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281relabeling and recreating the filesystem. It is even possible to fsck the
282VN partitions that previously contained filesystems.
283.Pp
45e80934 284.Dl vnconfig -e -s reserve -S 400m vn1
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285.Dl disklabel -r -w vn1s0 auto
286.Dl newfs /dev/vn1s0
287.Dl mount /dev/vn1s0 /usr/obj
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288.Pp
289Is an example of a swap-backed VN disk configuration. This example assumes
290that you have at least 400 megabytes of swap free (and hopefully much more).
291The swap space is pre-reserved in order to maintain maximum performance.
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292We then label the disk, newfs it, and mount it as
293.Pa /usr/obj .
294Swap-backed VN
295devices are recoverable after a crash if you (A) use the reserve option, and if
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296(B) the same swap is reserved as was the last time, meaning that such
297vnconfig's would have to be run in your rc.local. In general, though, you
298only use swap-backed VN devices to hold information you don't mind losing
299on every reboot.
300.Sh SEE ALSO
301.Xr mount 2 ,
302.Xr swapon 2 ,
303.Xr unmount 2 ,
304.Xr vn 4