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Mac Forum / Programming / Mac Programming / July 2006Can't find partition-map area on new Intel Mac's drive - Where now?
Older OS X Macs had their partition map located in the very first 512-byte block on the disk drive. New Intel based Macs do not. I need to find start addresses of partitions, and size of partitions. That info' was normally stored in the partition map. Anyone know where the partition map was moved to? Normally, I could also get the needed partition info' by using Unix pdisk, as shown below - pdisk /dev/rdisk0 -dump However pdisk seems to be broken on Intel based Macs. Mark- > Older OS X Macs had their partition map located in the very first > 512-byte block on the disk drive. [quoted text clipped - 5 lines] > > Anyone know where the partition map was moved to? <http://developer.apple.com/documentation/MacOSX/Conceptual/universal_bin ary/universal_binary_diffs/chapter_3_section_10.html> Reinder > > Older OS X Macs had their partition map located in the very first > > 512-byte block on the disk drive. [quoted text clipped - 10 lines] > > Reinder Thanks, however still no joy from that website. All I could dig up there was general info' about creating partitions by using Mac OSX's built in "Disk Utility", working from the Mac's OS. What I need is info' about the whereabouts of the low level GUID Partition Table itself, on the internal drive of the new Intel based Macs. I have hunted in vain at a low hex level, trying to find where the GUID partition table was located on the internal disk of the Intel based Mac. Older Macs, (six months older), use a different type of partition map/table. It is called "Apple Partition Map" (APM). That partition map's critical data is located entirely on the very first 512-byte block of the internal disk drive of older Macs. It contains the name of all partitions, their size, their starting addresses, and total size of the entire internal disk drive. Also has info' about the start address and size of the disk driver software, used for all drives attached to the Mac. I can modify all that info' at a low hex level, which allows me to do things that are not possible, when working from the regular Mac OS. Must be something I am overlooking, because all the aforementioned data _has_ to be located somewhere on the internal drive of the newest Macs. ...back to searching for it manually. <sigh> Mark- > > > Older OS X Macs had their partition map located in the very first > > > 512-byte block on the disk drive. [quoted text clipped - 19 lines] > Partition Table itself, on the internal drive of the new Intel based > Macs. That site gives you the information that Intel Macs use EFI, and give a link to the EFI specification. AFAIK, the new partition format, GDT, is part of EFI. I expect that you will be able to find the info you want from the EFI web site, or from a site it links to, such as <http://www.uefi.org> Reinder > > Thanks, however still no joy from that website. > > [quoted text clipped - 14 lines] > > Reinder My problem with the website was that I did not dig deep enough. First, the acronyms: EFI = Extensible Firmware Interface basically the interface between the OS and the computer firmware, so the OS can "talk to" the computer's firmware. GUID = Globally Unique IDentifier a controversial long psuedo identifier number such as: 3F2504E0 4f89 11D3 9A 0C 03 05 E8 2C 33 01 ...used by Microsoft for their own anti-piracy reasons. Older versions of the GUID system were implicated in the Melissa worm. Since then, Microsoft has supposedly "fixed" the GUID system. Because the Intel Macintosh now uses a lot of Microsoft code, we will have to live with the controversial GUID system. gtp = a Unix tool that does the same chores on Intel Macs that pdisk does on older Macs GPT= Globally-unique-identifier Partition Table, which to avoid confusion can be thought of simply as: GPT = Global Partition Table the GPT basically does the same job on new Intel Macs as the old APM (Apple Partition Map) did with older Macs. *********************************** End of Acronyms My original aim to modify the GPT directly with a hex editor like "HexEdit" will not work, because the above described systems are complex and have safeguards built into them to prevent direct modification with a low level hex editor. (primarily checksums that can detect and prevent write attempts to the Global Partition Table) Any modification now has to be done with the approved Unix tool "gpt", which does the same things on Intel Macs that "pdisk" does on older Macs. gpt is a work in progress, however, so at this time it is still a wee bit buggy, according to its man page. That man page was written October 30, 2004. I do not think that a more recent version of gtp is available yet. Thanks again for digging up those websites for me, they helped a lot. Mark- |
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