Use Safe Mode on your Mac to troubleshoot problems

Computers are complex machines and this can make problems very hard to solve unless you are an expert. Although some faults have an obvious cause and are thus easy to fix, this is not always the case. What can you do? Starting in Safe mode can help you to solve Mac problems.

Problems can sometimes be infuriating and nothing you do seems to cure them. However, there are techniques that experts use to help identify the cause of problems and one of these is to use the many different ways of starting the Mac.

You may not be aware that there is in fact, more than one way to start it. You press the power button and it comes on. What else is there to the process? Quite a lot actually.

What is Safe Mode?

When OS X starts, some apps and services are loaded in the background automatically. You can see some of these by going to the Apple menu, System Preferences, Users and Groups, Login Items. An item listed here could be the cause of the problem you have with your Mac.

OS X startup programs

If you suspect that a login item is causing problems, select it in the list and click the minus button below. The entry for the item is deleted and it will not automatically start with OS X. This does not delete the app from the disk, just the login Items list.

There are other startup items that are hidden unless you know how to find them. Hold down the Option key, click the Go menu and select Library. Open LaunchAgents and the items listed here also load automatically when OS X starts.

Command click the LaunchAgents name in Finder title bar and select the Mac from the menu to go to the root of the disk drive. Open the Library and there is another LaunchAgents folder and just below it is LaunchDaemons. Both of these can contain more apps and services that are started automatically with OS X.

OS X startup programs

There can be a lot of background items starting with OS X and when you have a problem with no obvious cause, one useful tool for identifying the cause is to start in Safe Mode. This starts the Mac with the absolute minimum of extras like startup items, which are not core functions of the operating system.

If the Mac starts up in Safe Mode and does not exhibit the problem you have been having, it narrows down the cause to software that is loading with OS X. More specifically, it is software you have added. Knowing this, you can then look at the startup items, see what is running, and remove or update them.

If the problem persists even in safe mode, then it probably is not any of the apps you have installed and it is a more fundamental problem with the Mac’s hardware or OS X itself.

Starting in Safe Mode does more than just prevent unnecessary extras from loading automatically and during the boot procedure, a check is made of the disk drive contents. The startup disk is verified and problems are repaired in a similar way to the functions that are available in Disk Utility (in the Applications/Utilities folder). It takes a bit longer to start up, so be patient.

Any font that you have added is disabled in Safe Mode, leaving on the system fonts. This means that if the problem is solved by Safe Mode, the cause could be corrupted fonts. (Fonts are loaded again when you restart in normal mode.) Fonts are cached (placed in a temporary store where they can be quickly accessed), and starting in Safe Mode moves the font caches to the Trash.

It is possible that simply starting up in Safe Mode and then restarting normally will fix whatever problem you are having. It depends on the cause, but repairing the disk and clearing the font cache will cure certain problems. It is certainly worth trying.

How do you start in Safe Mode?

Make sure the sound volume is turned up to maximum. If the sound is turned off, you will not be able to do this. Go to the Apple menu and select Shut down. When this has been done, wait a few seconds and then press the power button. As soon as you hear the startup tone, which is why you need to volume up, hold down the Shift key on the keyboard. Release the Shift key when the Apple logo and progress indicator appears.

What if this does not work?

There is a way to tell the Mac to start in Safe Mode next time and this does not require you to hold down any keys. Go to the Applications folder, open the Utilities folder and start Terminal. At the command prompt, enter:

sudo nvram boot-args="-x"

Close the Terminal window and restart the Mac to start in Safe Mode.

Start the Mac in Safe Mode

Lots of things happen when the Mac starts up, but everything is hidden. This may include error messages too. To start in Safe Mode and display all startup messages, use this command instead in the Terminal window:

sudo nvram boot-args="-x -v"

The -x means start in Safe Mode and -v stands for verbose, in other words show every status message on the screen.

This above command is stored and is permanent until it is cancelled. To start the Mac in normal mode you must enter this command into the Terminal window:

sudo nvram boot-args=""



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