md.4 revision 114098
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"THE BEER-WARE LICENSE" (Revision 42):
<phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
can do whatever you want with this stuff. If we meet some day, and you think
this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
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$FreeBSD: head/share/man/man4/md.4 114098 2003-04-27 01:46:56Z dougb $
.Dd March 9, 2001 .Dt MD 4 .Os .Sh NAME .Nm md .Nd memory disk .Sh SYNOPSIS .Cd device md .Sh DESCRIPTION The .Nm driver provides support for four kinds of memory backed virtual disks: l -tag -width preload t Cm malloc Backing store is allocated using .Xr malloc 9 . Only one malloc-bucket is used, which means that all .Nm devices with .Cm 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 .Xr vmstat 8 . t Cm preload A file loaded by .Xr loader 8 with type .Sq md_image is used for backing store. For backwards compatibility the type .Sq mfs_root is also recognized. If the kernel is created with option .Dv MD_ROOT the first preloaded image found will become the root file system. t Cm vnode A regular file is used as backing store. This allows for mounting ISO images without the tedious detour over actual physical media. t Cm swap Backing store is allocated from swap space. .El
"THE BEER-WARE LICENSE" (Revision 42):
<phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
can do whatever you want with this stuff. If we meet some day, and you think
this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
----------------------------------------------------------------------------
$FreeBSD: head/share/man/man4/md.4 114098 2003-04-27 01:46:56Z dougb $
.Dd March 9, 2001 .Dt MD 4 .Os .Sh NAME .Nm md .Nd memory disk .Sh SYNOPSIS .Cd device md .Sh DESCRIPTION The .Nm driver provides support for four kinds of memory backed virtual disks: l -tag -width preload t Cm malloc Backing store is allocated using .Xr malloc 9 . Only one malloc-bucket is used, which means that all .Nm devices with .Cm 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 .Xr vmstat 8 . t Cm preload A file loaded by .Xr loader 8 with type .Sq md_image is used for backing store. For backwards compatibility the type .Sq mfs_root is also recognized. If the kernel is created with option .Dv MD_ROOT the first preloaded image found will become the root file system. t Cm vnode A regular file is used as backing store. This allows for mounting ISO images without the tedious detour over actual physical media. t Cm swap Backing store is allocated from swap space. .El
p For more information, please see .Xr mdconfig 8 . .Sh SEE ALSO .Xr disklabel 5 , .Xr disklabel 8 , .Xr fdisk 8 , .Xr loader 8 , .Xr mdconfig 8 , .Xr mdmfs 8 , .Xr newfs 8 , .Xr vmstat 8 .Sh HISTORY The .Nm driver first appeared in .Fx 4.0 as a cleaner replacement for the MFS functionality previously used in .Tn PicoBSD and in the .Fx installation process.
p The .Nm driver did a hostile takeover of the .Xr vn 4 driver in .Fx 5.0 . .Sh AUTHORS The .Nm driver was written by .An Poul-Henning Kamp .Aq phk@FreeBSD.org .