[Dr-NiKoN]

Q: What is "repair permissions."
A: It is a utility that will revert the permissions on your system to a state that is documented in receipts from previously installed parts of your system. An example: Repair permissions should not touch anything in your home-folder.

code:


[Tor:/Library/Receipts] tor% ls

ARDClient124Update.pkg          QuickTime651.pkg

AirPortExtreme3.4.2.pkg         Safari_1.2.pkg

AirPortSW.pkg                   SecUpd2004-02-23Pan.pkg

AirPortUpdate3.3.1.pkg          SecUpd2004-04-05Pan.pkg

ApplicationsServerDev.pkg       SecUpd2004-05-03Pan.pkg

AsianLanguagesSupport.pkg       SecUpd2004-05-24Pan.pkg

BSD.pkg                         SecUpd2004-06-07Pan.pkg

BSDSDK.pkg                      SecurityUpd2003-11-19.pkg

BaseSystem.pkg                  SecurityUpd2003-12-05.pkg

BatteryUpdate.pkg               SecurityUpd2003-12-19.pkg

BluetoothFirmwareUpdate1.1.pkg  SecurityUpd2004-01-26Pan.pkg

BluetoothUpdate1.5.pkg          StuffItExpander.pkg

BluetoothUpdate141.pkg          X11SDK.pkg

DevDocumentation.pkg            X11User.pkg

DevExamples.pkg                 XcodeUpdate1.1.pkg

DevSDK.pkg                      iCal.pkg

DeveloperTools.pkg              iChatAV21.pkg

Essentials.pkg                  iMovie.pkg

Fink 0.6.2 Installer.pkg        iPhoto.pkg

Java.pkg                        iPod131.pkg

Java142.pkg                     iPod2004-07-15.pkg

Keynote.pkg                     iPod21.pkg

MacOSXUpdate10.3.1.pkg          iPodWeb2004-04-28.pkg

MacOSXUpdate10.3.2.pkg          iPodmini10.pkg

MacOSXUpdate10.3.3.pkg          iSync.pkg

MacOSXUpdate10.3.4.pkg          iTunes.pkg

MediaFiles.pkg                  iTunes4.pkg

MicrosoftIE.pkg                 wxPythonOSX-panther.pkg

QuickTime65.pkg

---

The only real receipt that could fix problems would normally be BaseSystem.pkg and BSD.pkg.
To figure out what exactly repair permissions does, you can go into every .pkg-file/Contents/ and check out Archive.bom. It will show the information that "repair permissions" use to do it's stuff.
Here is an example from /Library/Receipts/BaseSystem.pkg/Contents/Archive.bom

code:


./Library/Documentation 40775   0/80

./Library/Documentation/Acknowledgements.rtf    100664  0/80    219723  4181189441

./Library/Filesystems   40775   0/80

./Library/Filesystems/AppleShare        40775   0/80

./Library/Filesystems/AppleShare/Authentication 40775   0/80

./Library/Keyboard Layouts      40775   0/80

./Library/Preferences   40775   0/80

./Library/Preferences/SystemConfiguration       40755   0/80

./Library/Preferences/SystemConfiguration/preferences.plist     100644  0/80    3223    3283042560

./System/Library        40755   0/0

---

The first number after the directory-path is the permissions that the installer did set upon installation, and is thus conceived to be correct.
Also note, there is no documentation about conflicts. So, if you install an app that chances the permissions set by a previous package, you can't really know which one is conceived as correct. I'm to lazy to try and figure out how Apple handles this, because really I don't care. Also, there is no way for this "Repair Permissions" utility to know which one is correct.
And, to get to the point:
Repair Permissions is not based on Volumes or where OS X is installed. It's based on what the receipts of installed .pkg's says.