I’m getting more and more calls and emails from friends and family regarding startup problems with their Macs. This seems to be especially true for the iMacs.

So I’ve put together a list of the best ways to fix these problems. If your Mac hangs on a white screen or just won’t start up normally, there are a number of things you can do to try to fix the problem. It should be noted that if you have a hardware problem (e.g., bad hard drive, bad memory, bad power supply, etc.) these fixes won’t help. If you have a hardware problem, the best course of action is to visit your Apple dealer for a diagnosis.

Zap The PRAM

The first and easiest thing you can do is “zap the PRAM”. This means clearing out the parameter RAM (Random Access Memory), which can sometimes get messed up if you shutdown improperly or the power is cut mid-stream for some reason. This will often fix many startup problems. Here’s the procedure:

1. Turn computer off by holding power button down until computer turns off
2. Turn computer on and immediately hold down all four keys: Option + Command + p + r  Continue to hold all 4 keys down until you hear the computer chime twice
3. After the second chime (the startup sound) lift fingers off of keys and let the computer start up normally

If this procedure doesn’t fix your problem, then we need to get a little more serious and give your Mac a boot.

Safe Boot

A Safe Boot is a way to start your Mac and perform certain checks. It also prevents some software (which can be the source of startup problems)  from automatically loading. Here’s the procedure:

1. Make sure your Mac is shutdown
2. Press the power button to turn on Mac
3. Immediately after you hear the startup tone, hold the Shift key
4. Release the Shift key when you see the gray Apple logo

The system will perform certain checks and repair them if possible. Although a Safe Boot may allow you to now proceed with the login, this mode has disabled many startup items, some fonts, and possibly other software that you may be accustomed to using. So, the best thing to do is restart your computer normally and see if the problem has been resolved.

If you are still having problems, we have one more trick up our sleeve.

Single-User Mode

The Single-User mode gets you deeper into the Mac’s operating system without the nice user interface. This mode gets you only text on the screen. It also gets you into a mode where you are less protected from causing some damage to the system if you are not careful. So be careful to closely follow directions here. Here’s the procedure:

1. Make sure your Mac is shutdown
2. Press the power button to turn on Mac
3. Immediately press and hold the Command + s keys

You know when you’re in Single-User mode when you see a bunch of white text on the screen. It may be a little scary if you haven’t been in the command-line mode before on your computer. Wait for the text to come to a rest at the command prompt, which may look like this:

:/ root#

At this prompt, type the following very carefully:

/sbin/fsck -fy

Then hit the Return key.

This process can take several seconds up to a few minutes to perform. Be patient. The text will indicate each check that is taking place. Some checks will occur quickly, others will take some time. You may also see text that indicates that some repairs are taking place.

Do not do anything to your Mac until you see something like the following prompt again:

:/ root#

The text will indicate status of your system and any repairs that may have occurred. If at this point the text indicates that a problem still exists, see this Apple forum discussion for further possible fixes: https://discussions.apple.com/thread/4693878

Now type the following in order to reboot your computer normally:

reboot

I hope this has helped you get your Mac back up and running. Feel free to add any comments or suggestions.