1 .\" ----------------------------------------------------------------------------
2 .\" "THE BEER-WARE LICENSE" (Revision 42):
3 .\" <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
4 .\" can do whatever you want with this stuff. If we meet some day, and you think
5 .\" this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
6 .\" ----------------------------------------------------------------------------
21 driver provides support for four kinds of memory backed virtual disks:
22 .Bl -tag -width preload
24 Backing store is allocated using
26 Only one malloc-bucket is used, which means that all
30 backing must share the malloc-per-bucket-quota.
31 The exact size of this quota varies, in particular with the amount
34 The exact value can be determined with
41 is used for backing store.
42 For backwards compatibility the type
45 If the kernel is created with option
47 the first preloaded image found will become the root file system.
49 A regular file is used as backing store.
50 This allows for mounting ISO images without the tedious
51 detour over actual physical media.
53 Backing store is allocated from swap space.
56 For more information, please see
59 To create a kernel with a ramdisk or MD file system, your kernel config
60 needs the following options:
61 .Bd -literal -ofset indent
62 options MD_ROOT #MD is a potential root device
63 options MD_ROOT_SIZE=8192 # 8MB ram disk
64 makeoptions MFS_IMAGE=/h/foo/ARM-MD
65 options ROOTDEVNAME=\"ufs:md0\"
69 will be loaded as the initial image each boot.
70 To create the image to use, please follow the steps to create a file-backed
74 Other tools will also create these images, such as NanoBSD.
87 driver first appeared in
89 as a cleaner replacement
90 for the MFS functionality previously used in
98 driver did a hostile takeover of the
105 driver was written by
106 .An Poul-Henning Kamp
107 .Aq phk@FreeBSD.org .