Jump to content

Talk:GUID Partition Table

Page contents not supported in other languages.
From Wikipedia, the free encyclopedia
This is an old revision of this page, as edited by Crackwitz (talk | contribs) at 20:29, 21 January 2019 (→Error in GPT disk layout figure). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.
WikiProject iconComputing: Software C‑class Mid‑importance
WikiProject iconThis article is within the scope of WikiProject Computing, a collaborative effort to improve the coverage of computers, computing, and information technology on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.ComputingWikipedia:WikiProject ComputingTemplate:WikiProject ComputingComputing
CThis article has been rated as C-class on Wikipedia's content assessment scale.
MidThis article has been rated as Mid-importance on the project's importance scale.
Taskforce icon
This article is supported by WikiProject Software (assessed as Mid-importance).

New version created by Scorpiuss

I've created a new version of the GPT page. The fundamentals are all there. Could use a chart of the things represented at each bit position. Microsoft's got a nice one on the external link indicated (which, by the way, is a great source).

-Scorpiuss, Aug 26 2005, 13:25 GMT

EFI System partition GUID contradiction

The GUID for an EFISys partition under the Partition Entries section is different than the one in the list of GUIDs. On the MS page linked at the bottom, the one given in the Partition Entries section is given.

-Scorpiuss

Error in GPT disk layout figure

I have been trying to understand the GPT disk layout. From reading the UEFI spec and other pages, my impression is that the secondary (alternate) GPT header is located in the last addressable block on the disk. However, the figure (GUID Partition Table Scheme) is not consistent. The caption says that -1 is the last addressable block, but following the same graphical logic as used at the top of the figure the figure indicates that the secondary GPT header starts at -2 and ends at -1, i.e., it indicates that that the secondary GPT header is located at the second addressable block from the end, which should be wrong.

Am I right in this? Who has made the figure and how can we modify it?

this is indeed misleading. the backup GPT header is in the very last LBA. nothing follows it. The figure must be fixed. I'll see if I can fix it. --Crackwitz (talk) 20:10, 21 January 2019 (UTC)[reply]
I meditated on this briefly. The alignment of the text relative to the dashed lines can be misleading. It was probably intended to be relative to blocks. "LBA-1" is beside the last block. It's not meant to label the dashed line. --Crackwitz (talk) 20:12, 21 January 2019 (UTC)[reply]
I made some edits: https://gist.github.com/crackwitz/e492e43cbf28d4a3877fe6108f99e6fa (vertically aligned the labels, added/removed some labels, removed some dividers) If anyone knows how to replace/overwrite a file in here, feel free to do it.--Crackwitz (talk) 20:29, 21 January 2019 (UTC)[reply]

Hello fellow Wikipedians,

I have just modified 3 external links on GUID Partition Table. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:

When you have finished reviewing my changes, you may follow the instructions on the template below to fix any issues with the URLs.

This message was posted before February 2018. After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than regular verification using the archive tool instructions below. Editors have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the RfC before doing mass systematic removals. This message is updated dynamically through the template {{source check}} (last update: 5 June 2024).

  • If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
  • If you found an error with any archives or the URLs themselves, you can fix them with this tool.

Cheers.—InternetArchiveBot (Report bug) 19:17, 9 October 2017 (UTC)[reply]

Endianness

This is a mess. Someone needs to go through all those GUIDs and check them. I can only check a few right now. To lay it out:

  • UUIDs, according to the RFC, are always written as hex integer ASCII strings (i.e. MSB first, the mathematical way)
  • the natural layout in memory would be exactly the same
  • some systems, such as Microsoft, and Intel who specified GPT, didn't feel like that and instead use mixed endian marshalling[1]
  • you can recognize the byte order a GUID was written in by checking its version field (most significant nibble in the third field, i.e. Vxxx) for a valid number. you'll notice that microsoft uses version 4 GUIDs. on-disk structures have that field in little endian, so the top four version bits sit like xxVx

Example: a "MS Reserved" partition (reserved for being turned into an EFI partition), has the bytes 16 E3 C9 E3 5C 0B B8 4D 81 7D F9 2D F0 02 15 AE on disk, but everyone agrees that the GUID is E3C9E316-0B5C-4DB8-817D-F92DF00215AE

So... #Partition_type_GUIDs has a footnote that explains this wrong. These GUIDs are written as specified. There's nothing little-endian about them.

I'll go ahead and fix this. My little explanation here because I know someone will need it.--Crackwitz (talk) 19:42, 21 January 2019 (UTC)[reply]

  1. ^ "Technical Note TN2166: Secrets of the GPT". Developer.Apple.com. Apple. 2006-11-06. Retrieved 2014-04-16.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Talk:GUID_Partition_Table&oldid=879528168"