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 .\" ----------------------------------------------------------------------------
17 To compile this driver into the kernel,
18 place the following lines in your
19 kernel configuration file:
20 .Bd -ragged -offset indent
24 Alternatively, to load the driver as a
25 module at boot time, place the following line in
27 .Bd -literal -offset indent
33 driver provides support for four kinds of memory backed virtual disks:
34 .Bl -tag -width preload
36 Backing store is allocated using
38 Only one malloc-bucket is used, which means that all
42 backing must share the malloc-per-bucket-quota.
43 The exact size of this quota varies, in particular with the amount
46 The exact value can be determined with
53 is used for backing store.
54 For backwards compatibility the type
57 If the kernel is created with option
59 the first preloaded image found will become the root file system.
61 A regular file is used as backing store.
62 This allows for mounting ISO images without the tedious
63 detour over actual physical media.
65 Backing store is allocated from buffer memory.
66 Pages get pushed out to the swap when the system is under memory
67 pressure, otherwise they stay in the operating memory.
70 backing is generally preferable over
75 For more information, please see
78 To create a kernel with a ramdisk or MD file system, your kernel config
79 needs the following options:
80 .Bd -literal -offset indent
81 options MD_ROOT # MD is a potential root device
82 options MD_ROOT_SIZE=8192 # 8MB ram disk
83 makeoptions MFS_IMAGE=/h/foo/ARM-MD
84 options ROOTDEVNAME=\\"ufs:md0\\"
89 will be loaded as the initial image each boot.
90 To create the image to use, please follow the steps to create a file-backed
94 Other tools will also create these images, such as NanoBSD.
105 driver first appeared in
107 as a cleaner replacement
108 for the MFS functionality previously used in
112 installation process.
116 driver did a hostile takeover of the
123 driver was written by
124 .An Poul-Henning Kamp Aq Mt phk@FreeBSD.org .