freebsd/sbin/mdconfig/mdconfig.8

.\" Copyright (c) 1993 University of Utah.
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.\" Copyright (c) 2000
.\"	Poul-Henning Kamp  All rights reserved.
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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
.\"
.\" $FreeBSD$
.\"
.Dd December 31, 2000
.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 s Ar size
.Op Fl f Ar file
.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.
.Pp
Options indicate an action to be performed:
.Bl -tag -width indent
.It Fl a
Attach a memory disk.
This will configure and attach a memory disk with the
parameters specified and attach it to the system.
.It Fl d
Detach a memory disk from the system and release all resources.
.It Fl t Ar type
Select the type of the memory disk.
.Bl -tag -width "preload"
.It 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.
.It Cm vnode
A file specified with
.Fl f Ar file
becomes the backingstore for this memory disk.
.It Cm swap
swapspace is used to back this memory disk.
.El
.It Fl f Ar file
Filename to use for the vnode type memory disk.
.It Fl l
List information about configured
.Xr md 4
devices.  If the
.Fl u
option is used in conjuction with this, the output is limited to
information on the specified device.
.It Fl n
When printing md device names, print only the unit number without the
md prefix.
.It Fl s Ar size
Size of the memory disk.
.Ar Size
is the number of 512 bytes sectors unless suffixed with a
.Cm k , m ,
or
.Cm g
which
denotes kilobyte, megabyte and gigabyte respectively.
.It Fl S Ar sectorsize
Sectorsize to use for malloc backed device.
.It Fl x Ar sectors/track
See description of
.Fl y 
below.
.It Fl y Ar heads/cylinder
For malloc 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.
.It Fl o Oo Cm no Oc Ns Ar option
Set or reset options.
.Bl -tag -width indent
.It Oo Cm no Oc Ns Cm reserve
Allocate and reserve all needed storage from the start, rather than as needed.
.It Oo Cm no Oc Ns Cm cluster
Enable clustering on this disk.
.It Oo Cm no Oc Ns Cm compress
Enable/Disable compression features to reduce memory usage.
.It 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.
.It Oo Cm no Oc Ns Cm readonly
Enable/Disable readonly mode.
.El
.It 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 :
.Pp
.Dl mdconfig -a -t malloc -s 4m
.Pp
To create a disk named
.Pa /dev/md4
with
.Pa /tmp/boot.flp
as backing:
.Pp
.Dl mdconfig -a -t vnode -f /tmp/boot.flp -u 4
.Pp
To detach and free all resources used by
.Pa /dev/md4 :
.Pp
.Dl mdconfig -d -u 4
.Pp
To create and mount a 128MByte swap backed file system on
.Pa /tmp :
.Bd -literal -offset indent
mdconfig -a -t swap -s 128M -u 10
newfs -U /dev/md10
mount /dev/md10 /tmp
chmod 1777 /tmp
.Ed
.Pp
To create a 5MB file-backed disk:
.Bd -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 .