Copyright (c) 1993 University of Utah.
Copyright (c) 1980, 1989, 1991, 1993
The Regents of the University of California. All rights reserved.
Copyright (c) 2000
Poul-Henning Kamp All rights reserved.

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the Systems Programming Group of the University of Utah Computer
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@(#)vnconfig.8 8.1 (Berkeley) 6/5/93
from: src/usr.sbin/vnconfig/vnconfig.8,v 1.19 2000/12/27 15:30:29

$FreeBSD: head/sbin/mdconfig/mdconfig.8 140627 2005-01-22 20:02:01Z pjd $

.Dd November 6, 2004 .Dt MDCONFIG 8 .Os .Sh NAME .Nm mdconfig .Nd configure and enable memory disks .Sh SYNOPSIS .Nm .Fl a .Fl t Ar type .Op Fl n .Oo Fl o Oo Cm no Oc Ns Ar option Oc ... .Op Fl f Ar file .Op Fl s Ar size .Op Fl S Ar sectorsize .Op Fl u Ar unit .Op Fl x Ar sectors/track .Op Fl y Ar heads/cyl .Nm .Fl d .Fl u Ar unit .Nm .Fl l .Op Fl n .Op Fl u Ar unit .Sh DESCRIPTION The .Nm utility configures and enables .Xr md 4 devices.

p Options indicate an action to be performed: l -tag -width indent t Fl a Attach a memory disk. This will configure and attach a memory disk with the parameters specified and attach it to the system. t Fl d Detach a memory disk from the system and release all resources. t Fl t Ar type Select the type of the memory disk. l -tag -width "preload" t Cm malloc Storage for this type of memory disk is allocated with .Xr malloc 9 . This limits the size to the malloc bucket limit in the kernel. If the .Fl o Cm reserve option is not set, creating and filling a large malloc-backed memory disk is a very easy way to panic a system. t Cm vnode A file specified with .Fl f Ar file becomes the backingstore for this memory disk. t Cm swap Swap space is used to back this memory disk. .El t Fl f Ar file Filename to use for the vnode type memory disk. t Fl l List configured devices. If given with .Fl u , display details about that particular device. t Fl n When printing md device names, print only the unit number without the md prefix. t Fl s Ar size Size of the memory disk. .Ar Size is the number of 512 byte sectors unless suffixed with a .Cm b , k , m , g , or .Cm t which denotes byte, kilobyte, megabyte, gigabyte and terabyte respectively. t Fl S Ar sectorsize Sectorsize to use for malloc backed device. t Fl x Ar sectors/track See the description of the .Fl y option below. t Fl y Ar heads/cylinder For .Cm malloc or .Cm vnode backed devices, the .Fl x and .Fl y options can be used to specify a synthetic geometry. This is useful for constructing bootable images for later download to other devices. t Fl o Oo Cm no Oc Ns Ar option Set or reset options. l -tag -width indent t Oo Cm no Oc Ns Cm async For .Cm vnode backed devices: avoid .Dv IO_SYNC for increased performance but at the risk of deadlocking the entire kernel. t Oo Cm no Oc Ns Cm reserve Allocate and reserve all needed storage from the start, rather than as needed. t Oo Cm no Oc Ns Cm cluster Enable clustering on this disk. t Oo Cm no Oc Ns Cm compress Enable/Disable compression features to reduce memory usage. t Oo Cm no Oc Ns Cm force Disable/Enable extra sanity checks to prevent the user from doing something that might adversely affect the system. t Oo Cm no Oc Ns Cm readonly Enable/Disable readonly mode. .El t Fl u Ar unit Request a specific unit number for the .Xr md 4 device instead of automatic allocation. .El .Sh EXAMPLES To create a 4 megabyte .Xr malloc 9 backed memory disk. The name of the allocated unit will be output on stdout like .Dq Li md3 :

p .Dl mdconfig -a -t malloc -s 4m

p To create a disk named

a /dev/md4 with

a /tmp/boot.flp as backing:

p .Dl mdconfig -a -t vnode -f /tmp/boot.flp -u 4

p To detach and free all resources used by

a /dev/md4 :

p .Dl mdconfig -d -u 4

p To create and mount a 128MByte swap backed file system on

a /tmp : d -literal -offset indent mdconfig -a -t swap -s 128M -u 10 newfs -U /dev/md10 mount /dev/md10 /tmp chmod 1777 /tmp .Ed

p To create a 5MB file-backed disk: d -literal -offset indent dd if=/dev/zero of=somebackingfile bs=1k count=5k mdconfig -a -t vnode -f somebackingfile -u 0 bsdlabel -w md0 auto newfs md0c mount /dev/md0c /mnt .Ed .Sh SEE ALSO .Xr md 4 , .Xr bsdlabel 8 , .Xr fdisk 8 , .Xr mdmfs 8 , .Xr malloc 9 .Sh HISTORY The .Nm utility first appeared in .Fx 5.0 as a cleaner replacement for the .Xr vn 4 and .Xr vnconfig 8 combo. .Sh AUTHORS The .Nm utility was written by .An Poul-Henning Kamp .Aq phk@FreeBSD.org .