How to fix your iMac if it fails to start? If you own a Mac and it fails to start or get stuck on a white or grey screen upon startup, you should understand that OS X or macOS have software or hardware problems.

How to Fix your iMac if it Fails to Start

Therefore, if your iMac won’t start up regularly, here are some things you can do to troubleshoot the problems:

• Run Disk utility

• Restart in Safe Mode

• Launch Single User Mode in the Terminal

• Reset NVRAM or PRAM

• Reinstall OS X or macOS

Before you try any of the above troubleshooting methods, you need to start by removing all peripherals from your Mac. First of all, disconnect all wired and wireless devices except your mouse and keyboard and then try rebooting. It is advisable to use an Apple-branded keyboard and a mouse that was shipped with your Mac when restarting. If your Mac will reboot after removing all the peripherals, it means that one of the peripherals is the problem. You can then add the peripherals one by one to determine the peripheral that causes problems. You may have to reboot your Mac severally when eliminating these peripherals.

1. Restart your Mac in a safe mode

Starting your Mac in a safe mode ensures that it checks your disk and repairs it while rebooting. Your mac’s launch database will be rebuilt on a hard drive to help your Mac reboot normally. It is important to note that rebooting in a safe mode is slower but it is because of disk checking and repair process. After you’ve rebooted in a safe mode, the first thing you need to do is empty your trash. This will provide more space on your mac to enable it to function normally. The second thing you need to do is to verify that Macintosh HD has at least 10 GB available space. If the hard drive does not have space, you need to move large files to another drive or even to an external drive to create more space. You should have at least 10 GB minimum on your hard drive to facilitate normal operation of your mac.

2. Run Disk utility To

Run disk utility, you need to turn off your mac and while you are turning it on, hold down the command and R keys until you see the Apple logo. After the logo appears, you should be able to see a Mac OS utilities or MacOS utility window. You should select disk utility, then click on your OS hard drive and then verify/repair the disk. After running the repair, the disk should run normally again.

However, if the disk is irreparable, the only solution is repairing the hard drive. Alternatively, if this is the first time that your hard drive has this problem, you can consider erasing the drive and restoring your data from a backup. However, if your disk fails one time, there are high chances that it will fail again. It is therefore advisable to replace it to avoid future problems.

3. Reset PRAM OR NVRAMPRAM or NVRAM

Refers to a small amount of space where your computer stores certain settings that macOS can access. If your mac isn’t booting normally, these settings might be faulty and the only way to fix them is by resetting PRAM or NVRAM. Some of the settings that are usually reset include your screen resolution, your mac speaker volume, startup disk selection, etc. After resetting NVRAM, you need to reconfigure the settings for your startup disk selection, speaker volume, screen resolution, and time zone information. However, if the startup problem persists after resetting your NVRAM, you need to replace your logic board battery. This is done by visiting an Apple Store an Authorized service provider to offer the required services.

4. Use Terminal in Single User Mode

In most cases, the 3 troubleshooting methods discussed above usually fixes the problem. However, if your iMac won’t boot still, there are a few steps you can try to fix the problem before you decide to reinstall macOS or Mac OS X. This final step involves running your mac in a single user mode using the command fsck i.e. File system check. Running your mac in this mode, you see commands scroll by on screen but when it stops you need to run the commands listed below to check whether your startup disk is having a problem. To start in a single user mode, restart your mac and when you hear the startup tone, press and hold command – s. You should hold these keys until you see a black screen with white letters. When this happens, you have rebooted your mac in a single user mode. You will then have to check your file system for consistency and remount the boot volume.

If this is not working, you can try using a terminal command which helps mac run check runs to determine its state. When a terminal command is completed, you will see either of these two messages: ‘Macintosh appears to be okay’ or ‘File System was modified’. Your subsequent steps will be determined by the message you will get. If you get the OK message, reboot your system and return to safe mode. However, if you get the message that the system was modified, repeat the terminal command until you get the OK message. After you get the OK message, command reboot your mac and perform a safe boot to ensure that the problem is fixed.

5. Reinstall MacOS or Mac OS X

If none of the above works, this is the only solution to your problem. You need to turn off your Mac and while turning it on, hold down the command and R keys until the Apple logo appears. You should then be able to see macOS utility window or Mac OS X utilities. Choose the reinstall option and reinstall your operating system.

Alternatively, you can reinstall your macOS from the internet rather than from your recovery partition. To achieve this, reboot your mac by holding down command + R. Release the keys once Apple logo appears and wait for internet reinstallation. Internet startup usually completes when you see the utility window. You need to choose to reinstall your Mac OS or Mac OS X from the utility window and then follow the instructions on your screen.

These five ways will help you fix your Mac if it won’t startup or if you have a white screen.

However, you need to be knowledgeable to know these commands or understand what you are supposed to do each and every time. It is important to understand that you may end up causing more damage or losing important files from your mac if you do it wrong. Therefore, if you don’t know how to do it yourself, seeking professional help is advisable. However, you can try reading online directions or watching videos online to help you do it yourself.