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2 files changed, 59 insertions, 0 deletions
diff --git a/NEWS b/NEWS
index 6c307067..81aadb0a 100644
--- a/NEWS
+++ b/NEWS
@@ -9,6 +9,9 @@ Changes in 1.65:
specify the initrd address limit.)
* Handle small "pseudo-kernels"; images that use the Linux
kernel boot protocols but are less than 64K in size.
+ * MEMDISK: New subsystem; this is a driver which allows
+ legacy OSes to boot using an in-memory simulated disk.
+ See memdisk/memdisk.doc for more info.
Changes in 1.64:
* Limited support for hardware flow control when using a
diff --git a/memdisk/memdisk.doc b/memdisk/memdisk.doc
new file mode 100644
index 00000000..e67000b9
--- /dev/null
+++ b/memdisk/memdisk.doc
@@ -0,0 +1,56 @@
+[This documentation is rather crufty at the moment.]
+MEMDISK is meant to allow booting legacy operating systems via PXE,
+and as a workaround for BIOSes where ISOLINUX image support doesn't
+MEMDISK simulates a disk by claiming a chunk of high memory for the
+disk and a (very small - 2K typical) chunk of low (DOS) memory for the
+driver itself, then hooking the INT 13h (disk driver) and INT 15h
+(memory query) BIOS interrupts.
+To use it, type on the SYSLINUX command line:
+memdisk initrd=diskimg.img
+... where diskimg.img is the disk image you want to boot from.
+[Obviously, the memdisk binary as well as your disk image file need to
+be present in the boot image directory.]
+... or add to your syslinux.cfg/pxelinux.cfg/isolinux.cfg something like:
+label dos
+ kernel memdisk
+ append initrd=dosboot.img
+Note the following:
+a) The disk image should *not* be compressed.
+b) If the disk image is one of the following sizes, it's assumed to be a
+floppy image:
+ 368,640 bytes - 360K floppy
+ 737,280 bytes - 720K floppy
+ 1,222,800 bytes - 1200K floppy
+ 1,474,560 bytes - 1440K floppy
+ 2,949,120 bytes - 2880K floppy
+For any other size, the image is assumed to be a hard disk image (and
+should typically have an MBR and a partition table.) Currently, the hard
+disk is always given the geometry of 16 heads, 63 sectors (the number of
+cylinders is derived from the image size) and should therefore be an even
+multiple of 516,096 bytes; in a future version I plan to examine the
+partition table to deduce the CHS geometry.
+SYSLINUX 1.65-pre4 does not contain what I would call a "release
+quality" version of MEMDISK, but it does seem to work (I have
+successfully booted DOS over the net using PXELINUX with it.) It
+contains an awful lot of debugging messages at this point, for one
+If you want to recompile it from sources, you will need to make sure that
+you have a fairly recent binutils installed. I have been using the
+binutils- RPM from RedHat.