OS X v10.11.1 - Frozen Login and/or Blank Screen After Login
The answer is: JUST ANGRILY RUN OVER THE PROBLEM
Boot into Safe Mode (holding down shift at the two separate appropriate moments, BTW OMGWTF). Safe mode still won't login, but now you have an option...
Get to a terminal, somehow.
I was able to use crazy circus methods to get one: I pressed the play/pause button on my keyboard to trigger iTunes to bring up a license agreement dialog box, this in turn brings up the menu bar, which I used to get to System Preferences, from there I used the "Secrets" prefpane (which was luckily already installed) to launch Firefox, thereafter I used a url handler to have firefox let me choose an application to open -- for example "Terminal" or "Quicksilver")
There must be a better way.
At the terminal, run this (all on one line):
sudo launchctl unload -w "/System/Library/LaunchDaemons/com.apple.mbsystemadministration.plist"
enter your password when prompted, then reboot.
If you know a better way to fix this issue, please share. If only launchctl unload -w from single-user-mode would work across reboots...
From safe-mode, before the fix, errors like these were getting logged:
Oct 22 13:12:41 unknown mbsystemadministration[272]: open on (null)/Library/Preferences/.GlobalPreferences.plist: File exists Oct 22 13:12:41 unknown com.apple.xpc.launchd[1] (com.apple.mbbackgrounduseragent): Service only ran for 0 seconds. Pushing respawn out by 10 seconds. Oct 22 13:12:41 unknown mbsystemadministration[272]: open on (null)/Library/Preferences/com.apple.HIToolbox.plist: File exists Oct 22 13:12:41 unknown mbsystemadministration[272]: open on (null)/Library/Preferences/com.apple.universalaccess.plist: File exists Oct 22 13:12:51 unknown com.apple.xpc.launchd[1] (com.apple.mbbackgrounduseragent): Service only ran for 0 seconds. Pushing respawn out by 10 seconds. Oct 22 13:13:01 unknown com.apple.xpc.launchd[1] (com.apple.mbbackgrounduseragent): Service only ran for 0 seconds. Pushing respawn out by 10 seconds.
The "mb" in "mbsystemadministration.plist" is "MacBuddy" as you can see by running:
strings '/System/Library/CoreServices/Setup Assistant.app/Contents/Resources/mbsystemadministration' | grep -i buddy
Note I'm removing some things for blog readability...
-[MBSAServer getBuddyUser:] -[MBSAServer postMacBuddyTasks:] -[MBSAServer preMacBuddyTasks:] -[MBSAServer terminateBuddySession:transitioningToUID:withCompletionBlock:] Buddy info dict we just wrote is invalid: %@ FacelessConfiguration: %@ skip buddy cookie FacelessConfiguration: skip buddy set Failed to remove MacBuddy automation cookie. Error: %@ LastSeenBuddyBuildVersion Removed MacBuddy automation cookie. Setting the MacBuddy Cookie ShowKeychainSyncBuddyAtLogin getBuddyUser: kPrimaryBuddyType kSecondaryBuddyType lastSeenBuddyBuildVersion lastSeenBuddyBuildVersion postMacBuddyTasks: preMacBuddyTasks: removeBuddyUserHome: removeResumeBuddyCookie: setLastSeenBuddyBuildVersion: setMacBuddyDoneCookie: setResumeBuddyCookie: setShowKeychainSyncBuddyAtLogin: setSkipBuddy: showKeychainSyncBuddyAtLogin showKeychainSyncBuddyAtLogin skipMiniBuddy switchToBuddySession: terminateBuddySession:transitioningToUID:withCompletionBlock: void MBSetTheMacBuddyCookie()
Separately, out of curiosity, I ran strings '/System/Library/CoreServices/Setup Assistant.app/Contents/Resources/mbsystemadministration' | grep '/' | sort | uniq to see what paths the program might be working with...
%@/Library/Preferences %@/Library/Preferences/%@ /Library/Documentation /Library/Logs/DiagnosticReports /Library/Preferences/%@ /System/Library/CoreServices/Language Chooser.app /System/Library/CoreServices/ManagedClient.app/Contents/MacOS/ManagedClient /Users/Shared/adi/adi-%08lX.pb /bin/cat /bin/chmod /etc/kcpassword /etc/kcpassword.mb /etc/ntp.conf /etc/resolver /sbin/mount /sbin/newfs_hfs /sbin/shutdown -h now /sbin/shutdown -r now /sbin/umount /usr/bin/certtool /usr/libexec/configureLocalKDC /usr/sbin/chown /usr/sbin/hdik /var/db/.AppleDiagnosticsSetupDone /var/db/.AppleLaunchMigration /var/db/.AppleSetupDebugInitialization /var/db/.AppleSetupDone /var/db/.AppleSetupDone22 /var/db/.AppleSetupResume /var/db/.AppleSetupUser /var/db/.InstallerConfiguration /var/db/.RunLanguageChooserToo /var/db/ConfigurationProfiles/.profilesAreInstalled /var/db/krb5kdc /var/root/.CFUserTextEncoding ram://100000
