MacFixIt Answers is a feature in which we answer questions e-mailed in by our readers.
This week people wrote in with questions how to manage corruption in the EFI boot loader in OS X or manage disks without one, the necessity of the OS X "periodic" scripts and whether or not they need to be rigorously scheduled, and a sudden instance where the desktop and screen contents appear larger than the size of the screen itself. We continually answer e-mail questions, and though we present answers here, we welcome alternative approaches and views from readers and encourage you to post your suggestions in the comments.
Question: Management for new or corrupted EFI boot loader files
MacFixIt reader Michael asks:
You state in your article [on the OS X boot process] that the Mac EFI is located inside the hard drive in a hidden partition. As a result this left me wondering about how a Mac with a new hard drive is able to boot up in the first place. Are the EFI partition files located in the Mac OS X install disk (or Recovery HD Internet Installation in OSX Lion) and created when you establish the partition table of the new drive or the EFI is embedded in the hardware? The second part of the question is, how likely is the chance that the EFI gets corrupted and if so how can one troubleshoot such issue on a Mac?
If you install a new hard drive, then when you install OS X the system will format the drive to contain this extra partition, and then place the boot.efi file on the partition so the system will quickly identify it as a drive containing a valid operating system.
The boot.efi loader is set up on the partition when you set it to be a boot drive, which can be done in the Startup Disk system preferences. If the file ever gets corrupted then the Mac's firmware will not immediately identify a boot drive. However, the firmware will then search the drive's contents for a boot loader, specifically in the /System/Library/CoreServices/ directory which is where the main boot loader is kept.
In doing this process the system will boot to the first found drive, unless you press the Option key at startup to load the boot menu. In the boot menu the system will again first scan the EFI partition for a valid boot loader, but if it cannot find one will then scan the drive's contents for the boot loader. When the system then boots properly to this drive, it will overwrite the boot loader in the EFI partition with the one in the OS X CoreServices folder, and thereby restore the functionality of the boot loader in the EFI partition.
Question: The necessity of the OS X "periodic" scripts
MacFixIt reader Constance asks:
Do you feel it is necessary or helpful to manually run the background maintenance tasks (daily, weekly, monthly) using something like Titanium's "Onyx" or "Maintenance" applications? I used to run the scripts regularly using Onyx or manually using Terminal when I had Tiger, but from some reading I have done it almost sounds like that isn't necessary any more. If the scripts do run automatically, do I have to leave the computers on at certain times or leave them sleeping at certain times or what?
The periodic scripts (daily, weekly, monthly) are set to run at 3:15 a.m. everyday for the daily tasks, on Saturday for the Weekly tasks, and at 5:30 a.m. on the first of every month for the Monthly tasks.
These scripts do not need to be run every day/week/month, and instead can each be run every week/month/year or so without hurting a thing, especially on a home system. You can change this scheduling if you would like by editing the launch daemon files for the scripts (located in the /System/Library/LaunchDaemons/ folder and are called "com.apple.periodic-TIME.plist"), or you can continue to use a third-party tool to run them manually. The system will not track whether you've missed a date for a specific script and then run it the next day. Instead it will just wait for the next day, week, or month to run the script.
These scripts are primarily used for managing system logs, network configurations, and temporary files which can be a burden to servers that stay on all the time, and have minimal impact on day-to-day activity for most home users.
The periodic scripts are just shell scripts that can be invoked manually without a third-party utility by running the following command in the Terminal:
sudo periodic TIME
Replace "TIME" with either "daily," "weekly," or "monthly" to run the desired scripts. After entering this command, you will need to supply your password.
Question: Screen appearing too big for the monitor
MacFixIt reader Jatrak asks:
I have a Mac Mini 2005 with Tiger. Everything works fine except that out of the blue the resoluton is too big for the screen and when I move the cursor the screen "adjusts," "pans" in the opposite direction. I went to Displays in System Preferences and made sure I was at the highest resolution. I was and the problem persists. Re-starting did not help. Do I need to go to an Apple Store? What to do?
It sounds like you have Apple's screen zooming feature enabled. Try pressing Option-Command-8 to disable it, or if that does not work then go to the Universal Access system preferences and turn off zooming in the "Seeing" section.