VNCONFIG(8) System Manager's Manual VNCONFIG(8) NAME vnconfig -- configure and enable vnode disks SYNOPSIS vnconfig [-cdeguvTZ] [-s option[,option...]] [-r option[,option...]] [-S value] special_file [regular_file] [feature] vnconfig -a [-cdeguv] [-s option] [-r option] [-f config_file] DESCRIPTION The vnconfig command configures and enables vnode pseudo disk devices. The first form of the command will associate the special file special_file with the regular file regular_file allowing the latter to be accessed as though it were a disk. Hence a regular file within the filesystem can be used for swapping or can contain a filesystem that is mounted in the name space. If you want to use swap backing store for your device instead of a file, you can leave regular_file out and specify the size of the block device with the -S option. Options indicate an action to be performed: -a Read a command file and performs the specified actions for each de- vice/file pair. -c Configure the device. If successful, references to special_file will access the contents of regular_file. -d Disable (if possible) the specified feature. -e Configure the device and enables any feature that was specified. If no feature was specified, -e is the same as -c. -f config_file Use config_file as an alternate config file. -g Fiddle global options. -r flag Reset flag. The list of allowed flags and their meanings are: labels use disk/slice labels. reserve Pre-reserve the blocks underlying the file or swap backing store. Currently only works for swap backing store. This option also disables on-the-fly freeing of the underlying backing store (for example, when you remove a large file). Use this option if you wish to avoid long-term fragmenta- tion of the backing store. Also note that when this option is used, the initial contents of the backing store may con- tain garbage rather then zeros. It may even be possible to recover the prior contents of a swap-backed VN across a re- boot if the VN device is configured before any swap is al- located by the system. follow debug flow in the vn(4) driver. debug debug data in the vn(4) driver. io debug I/O in the vn(4) driver. all turn on all flags. none turn off all flags. -s flag Set flag. The list of allowed flags and their meanings are the same as for the -r option. -S value{k,m,g,t} If no regular file is specified, VN will use swap for backing store. This option specifies the size of the device. For example, '23m' for 23 megabytes. The VN device will round the size up to a machine page boundary. Filesystems up to 7.9 terabytes are sup- ported. When specified along with a regular file, this option overrides the regular file's size insofar as VN is concerned. -T When a regular file is specified, VN will ftruncate() the file to 0 first. Normally you should also specify the -S option to set the size of the file. This option also creates the file if it did not previously exist. This option is only meaningful if the -S option has been specified. -Z When a regular file is specified, VN will zero the contents of the file to ensure that all blocks have been allocated by the filesys- tem. This option is only meaningful if the -S option has been specified. -u Disable and ``unconfigure'' the device. -v Print messages to stdout describing actions taken. If no action option is given, -c is assumed. The feature argument specifies a feature that can be enabled via the -e op- tion: swap Swapping is enabled on the special file. See swapon(2). mountro=mount_point The special file is mounted read-only on mount_point. See mount(2). mountrw=mount_point The special file is mounted read-write on mount_point. See mount(2). mount=mount_point Same as ``mountrw=''. A configuration file contains one line per device/file pair in the form: special_file regular_file [ feature ] where fields are separated by white space. The previously described action options serve to configure, enable, disable or unconfigure all devices in the configuration file. FILES /etc/vntab default configuration file for -a option EXAMPLES vnconfig vn0c /tmp/diskimage Configures the vnode disk vn0c. vnconfig -e vn0c /var/swapfile swap Configures vn0c and enables swapping on it. vnconfig -d vn0c myfilesystem mount=/mnt Unmounts (disables) vn0c. vnconfig -ae Configures and enables all devices specified in /etc/vntab. vnconfig -s labels -c vn0 somebackingfile disklabel -r -w vn0 auto disklabel -e vn0 Is an example of how to configure a file-backed VN disk with a disk label and to initialize and then edit the label. Once you create the label, you can partition your VN disk and, for example, create a filesystem on one of the partitions. If you are using a file as backing store, it may be possi- ble to recover your VN disk after a crash by vnconfig'ing the same file again and using the VN configuration already stored in the file rather then relabeling and recreating the filesystem. It is even possible to fsck the VN partitions that previously contained filesystems. vnconfig -e -s labels,reserve -S 400m vn1 disklabel -r -w vn1 auto newfs /dev/vn1c mount /dev/vn1c /usr/obj Is an example of a swap-backed VN disk configuration. This example assumes that you have at least 400 megabytes of swap free (and hopefully much more). The swap space is pre-reserved in order to maintain maximum perfor- mance. We then label the disk, newfs it, and mount it as /usr/obj. Swap- backed VN devices are recoverable after a crash if you (A) use the reserve flag, and if (B) the same swap is reserved as was the last time, meaning that such vnconfig's would have to be run in your rc.local. In general, though, you only use swap-backed VN devices to hold information you don't mind losing on every reboot. SEE ALSO mount(2), swapon(2), unmount(2), vn(4) FreeBSD 4.5 July 8, 1993 VNCONFIG(8)
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