How to fix Mac startup problem: Blue or black screen

When you turn on your Mac, it should display a gray or dark, almost black screen as it searches for your startup drive. The color displayed will depend on the model and age of your Mac. Once the drive is detected, you will see a blue screen as your Mac loads the boot information from your startup drive and then displays the desktop.

Some Mac users will not see a blue or gray screen. With the advent of Retina displays and the expanded color spaces that the Mac now supports, old blue and gray screens can appear much darker, almost black on Macs that have built-in displays, making it difficult to discern the color of the screen. screen. If you are using an external display, you should be able to tell the difference between the gray and blue screens. We are going to call the screen colors by their old and classic names, although for some Mac users, the difference will be very difficult to detect as the screens will look almost black or black.

In this article, we will see why a Mac might get stuck on blue screen, and how to fix the problem.

The Mac Blue Screen of Death

If your Mac has hit the blue screen, we can rule out some potential issues right away. To get to the blue screen, your Mac has to turn on, run its basic self-test, check that the expected startup drive is available, and then start loading data from the startup drive. This is where it got stuck, which means your Mac is in pretty good shape overall, but your startup drive might be having some issues, or a peripheral connected to your Mac through a USB or Thunderbolt port is misbehaving.

peripheral problems

Peripherals, such as USB or Thunderbolt devices, can cause your Mac to stop at the blue screen. That’s why one of the first things to try if you see the blue screen is to unplug all peripherals from your Mac.

Although it’s possible to pull the USB or Thunderbolt cables from your Mac, it’s much better to shut down your Mac first. You can shut down your Mac by holding down the power button until it turns off. Once powered off, you can unplug the USB and Thunderbolt cables and then restart your Mac.

If unplugging peripherals from your Mac doesn’t fix the problem, continue with the startup drive repair.

Boot Drive Repair

Your startup drive may have one or more problems, many of which you can fix with Apple Disk Utility. You can also use a third-party application such as Drive Genius, TechTool Pro, or DiskWarrior to repair drive corruption. Since you can’t boot your Mac properly, you’ll have to boot from another drive that has a system on it or from a DVD installation disc. If you’re using OS X Lion or later, you can boot from the recovery disc; If you’re not sure how to do this, you’ll find instructions in the guide at the link below.

If you don’t have a startup option other than your usual startup drive, you can try to repair the drive by starting your Mac in single-user mode. This is a special startup environment that allows you to work with your Mac using commands that you can type in a terminal-like screen. (Terminal is a text-based application that ships with OS X or macOS.) Since single-user mode doesn’t require the boot drive to be fully functional, we can use some of the commands to perform repairs on the drive.

No matter which method you’re trying (another startup drive, a DVD, the recovery disc, or single-user mode), you’ll find step-by-step instructions in the How do I fix my hard drive if my Mac won’t boot? guide.

In most cases, repairing the drive will get your Mac working again, but keep in mind that a drive that has had these types of problems is likely to work again. Take this as an early warning that your boot drive is having problems, and consider replacing it soon. Be proactive and make sure you have backups or clones of your startup drive available.

Start permissions fix

Although repairing the startup drive should resolve the blue screen problem for most users, there is another less common issue that can cause a Mac to freeze on blue screen, and that is a startup drive that has its own issues. Incorrectly configured permissions.

This can happen as a result of a power outage or surge, or shutting down your Mac without going through the proper shutdown process. It can also happen to those of us who like to experiment with Terminal commands, and accidentally change the permissions of the boot drive to not allow any access. Yes, it is possible to configure a drive to deny all access. And if you do that to your startup disk, your Mac won’t boot.

We are going to show you two ways to fix a drive that was set to not have access. The first method assumes that you can start your Mac using another startup drive or an installation DVD. You can use the second method if you don’t have access to another boot device.

How to change startup drive permissions by booting from another device

  1. Start up your Mac from another startup device. To do this, start your Mac and hold down the options key. A list of available boot devices will appear. Select a device and your Mac will use it to finish booting up.
  2. Once your Mac shows the desktop, we’re ready to fix the permissions issue. Start Terminal, located in the /Applications/Utilities folder.
  3. Enter the following command in Terminal. Note that there are quotes around the boot drive path name. This is necessary to ensure that if the drive name contains special characters, including a space, it will work with the command. Be sure to replace the boot drive with the name of the boot drive that is having problems:

    sudo chown root “/Volumes/startupdrive/”

  4. Press Enter or Return.
  5. You will be prompted to provide your administrator password. Enter the information and press Enter or Return.
  6. Enter the following command (again, replace startupdrive with the name of your startup drive

    sudo chmod 1775 “/Volumes/startupdrive/”

  7. Press Enter or Return.

Your startup drive should now have the correct permissions and be able to boot your Mac.

How to change boot drive permissions if you don’t have another boot device available

  1. If you don’t have another boot device to use, you can change the boot drive’s permissions by using the special single-user boot mode.
  2. Start up your Mac while holding down the command and s keys.
  3. Hold down both keys until you see a few lines of text scrolling on the screen. It will look like an old-fashioned computer terminal.
  4. On the command line that appears after the text has stopped scrolling, enter the following:
     mount -uw/
  5. Press Enter or Return. Enter the following text:

    child root /

  6. Press Enter or Return. Enter the following text:
     chmod 1775 /
  7. Press Enter or Return. Enter the following text:


  8. Press Enter or Return.
  9. Your Mac will now boot from the startup drive.

If you still have problems, try repairing your startup drive using the methods described earlier in this article.