NAME    [Toc]    [Back]

     md -- memory disk

SYNOPSIS    [Toc]    [Back]

     device md

DESCRIPTION    [Toc]    [Back]

     The md driver provides support for four kinds of memory backed virtual
     disks:

     malloc   Backing store is allocated using malloc(9).  Only one mallocbucket
 is used, which means that all md devices with malloc
	      backing must share the malloc-per-bucket-quota.  The exact size
	      of this quota varies, in particular with the amount of RAM in
	      the system.  The exact value can be determined with vmstat(8).

     preload  A file loaded by loader(8) with type `md_image' is used for
	      backing store.  For backwards compatibility the type `mfs_root'
	      is also recognized.  If the kernel is created with option
	      MD_ROOT the first preloaded image found will become the root
	      file system.

     vnode    A regular file is used as backing store.	This allows for mounting
 ISO images without the tedious detour over actual physical
	      media.

     swap     Backing store is allocated from swap space.

     For more information, please see mdconfig(8).

SEE ALSO    [Toc]    [Back]

     disklabel(5), disklabel(8), fdisk(8), loader(8), mdconfig(8), mdmfs(8),
     newfs(8), vmstat(8)

HISTORY    [Toc]    [Back]

     The md driver first appeared in FreeBSD 4.0 as a cleaner replacement for
     the MFS functionality previously used in PicoBSD and in the FreeBSD
     installation process.

     The md driver did a hostile takeover of the vn(4) driver in FreeBSD 5.0.

AUTHORS    [Toc]    [Back]

     The md driver was written by Poul-Henning Kamp <phk@FreeBSD.org>.


FreeBSD 5.2.1			 March 9, 2001			 FreeBSD 5.2.1