* docs/grub.texi (Loopback booting): New section.

diff --git a/ChangeLog b/ChangeLog
index e8588f0a13304113e8058e56952009604556866c..69ccd49feed7530b13b0539ec7d468abdb5f131f 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,8 @@
-2011-12-19  Keshav P R  <the.ridikulus.rat@gmail.com>
+2011-12-22  Vladimir Serbinenko  <phcoder@gmail.com>
+
+       * docs/grub.texi (Loopback booting): New section.
+
+2011-12-22  Keshav P R  <the.ridikulus.rat@gmail.com>
 
        * util/grub-mkstandalone.in: Fix minor typo errors.
 

diff --git a/docs/grub.texi b/docs/grub.texi
index f2e19cc74dd370c96e273ac41cbfec146268df23..b8d59d7d9dd3301ccf42e612c171f04e5f0f6582 100644 (file)
--- a/docs/grub.texi
+++ b/docs/grub.texi
@@ -784,6 +784,7 @@ magic.
 
 @menu
 * General boot methods::        How to boot OSes with GRUB generally
+* Loopback booting::            Notes on booting from loopbacks
 * OS-specific notes::           Notes on some operating systems
 @end menu
 
@@ -855,6 +856,31 @@ required.  @xref{DOS/Windows}.
 
 Chain-loading is only supported on PC BIOS and EFI platforms.
 
+@node Loopback booting
+@section Loopback booting
+GRUB is able to read from an image (be it one of CD or HDD) stored on
+any of its accessible storages (refer to @pxref{loopback} command).
+However the OS itself should be able to find its root. This usually
+involves running a userspace program running before the real root
+is discovered. This is achieved by GRUB loading a specially made
+small image and passing it as ramdisk to the kernel. This is achieved
+by commands @command{kfreebsd_module}, @command{knetbsd_module_elf},
+@command{kopenbsd_ramdisk}, @command{initrd} (@pxref{initrd}),
+@command{initrd16} (@pxref{initrd}), @command{multiboot_module},
+@command{multiboot2_module} or @command{xnu_ramdisk}
+depending on the loader. Note that for knetbsd the image must be put
+inside miniroot.kmod and the whole miniroot.kmod has to be loaded. In
+kopenbsd payload this is disabled by default. Aditionally behaviour of
+initial ramdisk depends on command line options. Several distributors provide
+the image for this purpose or it's integrated in their standard ramdisk and
+activated by special option. Consult your kernel and distribution manual for
+more details. Other loaders like appleloader, chainloader (BIOS, EFI, coreboot),
+freedos, ntldr and plan9 provide no possibility of loading initial ramdisk and
+as far as author is aware the payloads in question don't support either initial
+ramdisk or discovering loopback boot in other way and as such not bootable this
+way. Please consider alternative boot methods like copying all files
+from the image to actual partition. Consult your OS documentation for
+more details
 
 @node OS-specific notes
 @section Some caveats on OS-specific issues