Q: Cannot install Mac EFI Security Update 2015-001

Launch the Console application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad and start typing the name.

Select

          /var/log ▹ install.log

from the log list on the left. If you don't see that list, select

          View ▹ Show Log List

from the menu bar at the top of the screen. The contents of the log will appear on the right. Each log message begins with a timestamp. Select the messages from the time of the last installation or update attempt. If you're not sure when that was, click the Clear Display button in the toolbar of the Console window and then try the installation again. Select the new messages that appear. Copy the messages to the Clipboard by pressing the key combination command-C. Paste into a reply to this message (command-V).

If there are runs of repeated messages, post only one example of each. Don’t post many repetitions of the same message.

When posting a log extract, be selective. Don't post more than is requested.

Please don't indiscriminately dump thousands of lines from the log into this discussion.

Please don't post screenshots of log messages—post the text.

Some private information, such as your name, may appear in the log. Anonymize before posting. You may need to use a text editor with search and replace, such as TextEdit.

When you post the log extract, you might see an error message on the web page: "You have included content in your post that is not permitted," or "The message contains invalid characters." That's a bug in the forum software. Please post the text on Pastebin, then post a link here to the page you created.

You're getting corrupt downloads. Usually that's due to network conditions. Try on another network, if possible.

Please read this whole message before doing anything.

This procedure is a diagnostic test. It’s unlikely to solve your problem. Don’t be disappointed when you find that nothing has changed after you complete it.

The purpose of the test is to determine whether the problem is caused by third-party software that loads automatically at startup or login, by a peripheral device, by a font conflict, or by corruption of the file system or of certain system caches.

Disconnect all wired peripherals except those needed for the test, and remove all aftermarket expansion cards, if applicable. Start up in safe mode and log in to the account with the problem.

Note: If FileVault is enabled in OS X 10.9 or earlier, or if a firmware password is set, or if the startup volume is a software RAID, you can’t do this. Ask for further instructions.

Safe mode is much slower to start up and run than normal, with limited graphics performance, and some things won’t work at all, including sound output and Wi-Fi on certain models. The next normal startup may also be somewhat slow.

The login screen appears even if you usually login automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.

Test while in safe mode. Same problem?

After testing, restart as usual (not in safe mode) and verify that you still have the problem. Post the results of the test.

I did try in safe mode

Did or did not?

This procedure will delete certain temporary and cache files used by system processes. The files are automatically generated and don't contain any of your data. Occasionally they can become corrupt and cause problems such as yours.

Back up all data before proceeding.

Triple-click anywhere in the line below on this page to select it:

/var/folders/zz

Right-click or control-click the highlighted line and select

          Services ▹ Reveal in Finder (or just Reveal)

from the contextual menu.* A folder should open with a subfolder named "zz" selected. Move that subfolder to the Trash. You may be prompted for your administrator login password. Restart the computer and empty the Trash.

*If you don't see the contextual menu item, copy the selected text to the Clipboard by pressing the key combination  command-C. In the Finder, select

          Go ▹ Go to Folder...

from the menu bar and paste into the box that opens by pressing command-V. You won't see what you pasted because a line break is included. Press return.

I don't have a better idea than what Apple suggested.