freebsd-src/sbin/mdconfig/mdconfig.8

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.\"	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 FreeBSD
.Sh NAME
.Nm mdconfig
.Nd configure and enable memory disks
.Sh SYNOPSIS
.Nm
.Fl a
.Fl t Ar type 
.Oo
.Fl o
.Oo Cm no Oc Ns Ar option
.Oc
.Op Fl b Ar baseaddress
.Op Fl s Ar size
.Op Fl f Ar file
.Op Fl u Ar unit
.Nm
.Fl d
.Fl u Ar unit
.Sh DESCRIPTION
The
.Nm
command 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 preload
This type represents memory disks which are backed by memory outside
the kernels normal address space.
These can be instantiated automatically by objects loaded by the
bootloader or configured on the fly.
.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 b Ar baseaddress
Starting address in kernel virtual space of the memory to be used for a
.Cm preload
type disk.
.It Fl f Ar file
Filename to use for the vnode type memory disk.
.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 Xo
.Fl o Oo Cm no Oc Ns Ar option
.Xc
Set or reset options.
.Bl -tag -width indent
.It Xo
.Oo Cm no Oc Ns Cm reserve
.Xc
Allocate and reserve all needed storage from the start, rather than as needed.
.It Xo
.Oo Cm no Oc Ns Cm cluster
.Xc
Enable clustering on this disk.
.It Xo
.Oo Cm no Oc Ns Cm autounit
.Xc
Automatically allocate the next free unit number for this disk.
The basename of the disk is printed on stdout.
.It Xo
.Oo Cm no Oc Ns Cm compress
.Xc
Enable/Disable compression features to reduce memory usage.
.It Xo
.Oo Cm no Oc Ns Cm readonly
.Xc
Enable/Disable readonly mode.
.El
.It Fl u Ar unit
Force the
.Xr md 4
device to use a specific unit number.
.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 filesystem on
.Pa /tmp :
.Bd -literal -offset indent
mdconfig -a -t swap -s 128M -u 10
disklabel -r -w md10 auto
newfs -f 4096 /dev/md10c
tunefs -n enable /dev/md10c
mount /dev/md10c /tmp
.Ed
.Pp
It is practically impossible to give a universal example of the
.Cm preload
type of disk, it is mainly useful in the embedded systems market,
but to give a feel for how it works:
On most standard PC architecture machines this will create a disk
backed by the BIOS ROM:
.Pp
.Dl mdconfig -a -t preload -s 128k -b 0xc00fe000
.Sh SEE ALSO
.Xr md 4 ,
.Xr disklabel 8 ,
.Xr fdisk 8 ,
.Xr malloc 9