If your Mac only shows the blue screen on startup, or you can log in but the desktop doesn’t appear, you may have a problem with your startup drive. The usual course of action is to run Disk Utility to try and repair your startup drive, but you can’t do that if your Mac won’t boot, right? Well this is what you can do.
When a Mac won’t start normally, one of the most common troubleshooting practices is to check and repair the startup drive. A problem startup drive is likely to prevent your Mac from booting, so you may be in for a tough spot. You need to run the Disk Utility first aid tools, but you can’t access Disk Utility because your Mac won’t start.
There are three methods to get around this problem.
- Boot from a different device. This can be another drive that has a bootable system, or your OS X install DVD, which also contains the Disk Utility tools, or the Recovery HD which is a special partition on your startup drive that has been present from OS X Lion and later.
- Failsafe mode. This is a special startup method that forces your Mac to perform an automatic disk check and repair while trying to boot.
- Single User Mode (fsck). This is another special startup method that allows you to run command line utilities, such as fsck, that can check and repair hard drives.
Boot from an alternate device
The easiest solution by far is to boot from a different device. The three most popular options are another bootable drive, an emergency boot device such as a bootable USB flash drive, or a current OS X install DVD.
To boot from another hard drive or USB flash device, hold down the options key and start up your Mac. The Mac OS boot manager will appear, allowing you to select the device to boot from.
To boot from the OS X installation DVD, insert the DVD into your Mac, then restart your Mac while holding down the letter ‘c’ key.
To boot from the recovery hard drive, restart your Mac while holding down the command (cloverleaf) and R (command + R) keys.
Once your Mac finishes booting up, use Disk Utility’s First Aid feature to check and repair your hard drive.
Boot using Safe Mode
To boot into Safe Mode, hold down the Shift key, and then boot up your Mac. Safe Mode takes a while, so don’t be alarmed when you don’t see the desktop right away. While it waits, the operating system checks the directory structure of your boot volume and repairs it, if necessary. It will also remove some of the startup caches that may also be preventing your Mac from starting properly.
Once the desktop appears, you can access and run the Disk Utility First Aid tool as you normally would. When first aid is done, restart your Mac normally.
Please note that not all applications and features of OS X will work when booted into Safe Mode. You should use this startup mode only for troubleshooting and not for running everyday applications.
Boot into single user mode
Start up your Mac and immediately hold down the command key plus the letter ‘s’ (command + s). Your Mac will start up in a special environment that looks like an old-fashioned command line interface (because that’s exactly what it is).
At the command line, type the following:
/sbin/fsck -fy
Press return or enter after typing the above line. Fsck will boot and display status messages about your boot disk. When it’s finally done (this may take a while), you’ll see one of two messages. The first indicates that no problems were found.
The second message indicates that problems were found and fsck tried to fix the errors on your hard drive.
******* FILE SYSTEM WAS MODIFIED *****
If you see the second message, you should repeat the fsck command again. Keep repeating the command until you see the message “volume xxx appears to be OK”.
If you don’t see the volume OK message after five or more attempts, your hard drive may have serious problems that you can’t recover from.