--- /dev/null
+This directory contains the source code for gptsync, which is a program for
+creating hybrid MBRs (http://www.rodsbooks.com/gdisk/hybrid.html).
+
+HYBRID MBRS ARE UGLY AND DANGEROUS HACKS, AND SHOULD NOT BE USED UNLESS
+ABSOLUTELY NECESSARY!
+
+Despite their dangers, hybrid MBRs are useful because Windows interprets
+hybrid MBR disks as having an MBR partition table, whereas OS X and Linux
+interpret such disks as having a GUID partition table (GPT). Since Windows
+ties its boot mode to the firmware type (MBR/BIOS and GPT/EFI), a hybrid
+MBR enables Windows to boot in BIOS mode from a disk that's primarily a GPT
+disk, such as a Macintosh OS X disk.
+
+Unfortunately, Apple uses hybrid MBRs as part of its workaround to enable
+Macs to boot Windows in BIOS mode while also supporting a standard EFI-mode
+boot of OS X. Many Linux distributions also install in BIOS mode on Macs,
+and so use hybrid MBRs; but it's usually possible to add an EFI-mode boot
+loader to get Macs to boot Linux in EFI mode, thus obviating the need for a
+hybrid MBR. Some Hackintosh installations rely on a hybrid MBR for reasons
+similar to those of OS X on a real Mac. Thus, you should use a hybrid MBR
+*ONLY* on a Mac that dual-boots with Windows or some other OS in BIOS mode
+or in very rare circumstances on other computers.
+
+The version of gptsync provided with rEFInd is heavily modified from the
+original rEFIt version of the program. Most notably, it's "smarter" about
+creating a hybrid MBR: It prioritizes placement of Windows (FAT and NTFS)
+partitions in the MBR side, followed by Linux partitions. Other partitions,
+such as OS X's HFS+ partitions, might not appear at all in the hybrid MBR,
+whereas they generally do appear in hybrid MBRs created by rEFIt's version
+of gptsync. In the rEFIt version of gptsync, OS X partitions can crowd out
+FAT or NTFS partitions, particularly on computers with shared FAT or NTFS
+partitions, multiple Windows installations, or triple-boots with OS X,
+Windows, and Linux. The rEFInd version of gptsync also checks the
+firmware's author and warns if you're trying to run the program on anything
+but Apple firmware, since in most such cases creating a hybrid MBR is *NOT*
+desirable.
+
+Although the Makefile supports building for both EFI (via the "gnuefi" and
+"tiano" targets) and Unix/Linux (via the "unix" target), the Unix build is
+currently broken; it returns a bogus error about an unknown GPT spec
+revision. If you want to create a hybrid MBR in an OS, you're better off
+using gdisk (http://www.rodsbooks.com/gdisk/), which provides much better
+control of the hybrid MBR creation process. gdisk may also be preferable if
+you have an unusual partition layout, many partitions, or specific
+requirements that you understand well.