Bootable USBs for Mac OS

by

Your Comprehensive FAQ Companion

Here’s a collection of Frequently Asked Questions that people often ask when they’re using a bootable USB flash drive on a Mac. Bootable USBs for Mac OS can sometimes create problems for Mac users. This list will provide answers to the questions most people ask us about.

For more help reach out to us through our Contact US page. Our commitment is to reply to all queries within 2 hours during our regular business hours. We’re here to provide assistance and support, always ready to lend a hand.

I just purchased a used Mac and I am unable to install macOS from the bootable USB, the error is “macOS can’t be installed”.

Many times the previous owner of the Mac while removing their personal files from the hard drive also deleted some required Mac OS system files which prevents the macOS installer from completing. To fix this problem follow the steps below:

  • Boot from the macOS USB flash drive.
  • Select Disk Utility from the menu.
  • Delete the old macOS partition on the hard drive.
  • Create a new macOS partition.
  • Exit Disk Utility.
  • Select Install macOS and follow the on-screen instructions.
I get an error “This copy of the Installer application can’t be verified. It may have been corrupted or tampered with during downloading.” What should you do?

When you try to install macOS you may get an error message on some Macs due to a known date bug with the Apple Installer. You may see something like “An error occurred while preparing the installation” or “This copy of macOS is damaged and cannot be used to install macOS”. While this is a vague message that could mean just about anything, it could be just a matter of time, that is your Mac’s clock. This message is often caused by an incorrect time and date on the Mac for the macOS Installer. To fix the problem follow the steps below.

For macOS 10.13 High Sierra and earlier versions of macOS:
  • Make sure your computer is not connected to the internet.
  • Open the Terminal applications in the Utilities folder located in Applications folder.
  • Type “date 031918152017” and press return. This will backdate the clock to workaround the known date issue.
  • To confirm that the date has been changed type “date” and press return in the terminal window. You should see March 19 6:15:10 PDT 2017. You can also type “date help” for more information on the date command syntax.
  • If the date command produces an error such as “Permission denied” or “Operation not permitted,” you can easily rectify the situation by adjusting your clock using the Date and Time app located in System Preferences. Make sure the computer is not linked to the internet to prevent automatic resetting of the clock by the Apple Internet Time Server.
  • You should now be able to run the macOS installer without getting an error message.
For versions of macOS 10.14 Mojave and newer:
  • Ensure the computer is disconnected from the Internet.
  • Open the Terminal applications in the Utilities folder located in the Applications folder.
  • Type “date 030518152022” and press return. This will backdate the clock to work around the known date issue.
  • To verify the date change, type “date” in the terminal window and press “return.” You should see March 5 6:15:10 PDT 2022. You can also type “date help” for more information on the date command syntax.
  • If the date command returns an error such as “Permission denied” or “Operation not permitted,” then simply set your clock back using the Date and Time app in System Preferences. Ensure that you disconnect your computer from the internet to prevent the internet time server from automatically resetting the clock.
  • You should now be able to run the macOS installer without getting an error message.
How do I boot from to a bootable macOS USB flash drive?     FAQ - Mac OS Bootable USB Flash Drives
  • With the Mac off, plug the USB into a USB port on your computer.
  • Press the power button and when you hear the Startup Sound press and hold the Option key until you see the Startup Manager screen.
  • On the startup manager screen you should see your hard drive on the left and the USB on the right.
  • Press the Right-Arrow key to select the USB and press Return.
  • Your Mac to then boot from the USB and load the macOS Installer.
  • Just follow the on screen instructions to complete your macOS install.
When I try to boot from the macOS USB I get a circle with a line through it on my screen, what does that mean?

When you see a circle with a line through it (a circle with a slash) on your screen while trying to boot from a macOS USB, it typically indicates that your Mac cannot find a valid system to start up from. Also known as the “prohibitory sign.”

  • There could be several reasons for this issue:
  • Incompatible macOS version: The macOS version on the USB might not be compatible with your Mac model. Please make sure that your specific Mac supports the macOS version you are attempting to install.
  • Corrupt files or faulty USB: A corrupted macOS installation can occur due to either corrupted files on the USB or a faulty USB drive. Try creating a new macOS bootable USB using a different USB drive and a reliable method.
  • Hardware issues: There could be hardware problems with your Mac, such as a failing hard drive or SSD, which prevent the system from booting correctly.
  • Incorrect boot settings: Ensure that you set your Mac to boot from the USB drive to avoid incorrect boot settings. To do this, restart your Mac and hold down the Option (⌥) key immediately after you hear the startup chime. This will bring up the Startup Manager, where you can select the USB drive to boot from.
  • Secure Boot settings: Some Macs have Secure Boot options that may prevent booting from external drives. Check your Mac’s firmware settings and disable Secure Boot if necessary.
  • File system Format: Make sure to format the USB drive correctly with a macOS-compatible file system (typically macOS Extended Journaled or APFS) for proper functionality.
To troubleshoot the issue, try the following steps:
  • Verify the macOS version: Ensure that you are using a compatible macOS version for your Mac model.
  • Create a new macOS bootable USB: Use a different USB drive and a reliable method to create a new bootable macOS installer.
  • Check hardware: Run hardware diagnostics on your Mac to identify any hardware issues.
  • Check USB port and cable: Try using a different USB port and cable to rule out any issues with the connectivity.
  • Reset NVRAM/PRAM: Resetting the NVRAM (non-volatile random-access memory) or PRAM (parameter random-access memory) can sometimes resolve boot-related problems. Restart your Mac and hold down Command (⌘) + Option (⌥) + P + R until you hear the startup chime twice.

If none of these steps resolve the issue, it might be best to seek help from an authorized Apple service provider or Apple Support to diagnose and fix the problem. They can provide specific guidance based on your Mac model and the macOS version you are trying to install.

How can I check the model and year of my Mac?

You can easily find out the model and year of your Mac by following these steps:

  • Click on the Apple logo in the top-left corner of your screen to open the Apple menu .
  • Select “About This Mac” from the menu. This will open a window displaying information about your Mac.
  • In the “Overview” tab, you will see information about the model year of your Mac. Your Mac model should be listed as “MacBook Pro (13-inch, 2020)” or “iMac (27-inch, Late 2019),” for example, depending on your specific device.
  • If you want more detailed information, you can click on the “System Report” button. This will open the System Information application.
  • In the System Information application, under the “Hardware” section in the left sidebar, you will find “Model Identifier.” This identifier consists of numbers and letters that uniquely identify your Mac model. You can use this identifier to look up more specific information about your Mac online.

Using these steps, you can easily determine the model and year of your Mac computer. You can also find additional information on Apples web site on How to Identify Your MacBook Model.

I don’t see the answer to my question here so how do I get additional help?
  • You can contact us via our Contact US page. We do our best to replay to all questions within 2 hours during normal business hours and we are always glad to help.
  • We also have additional Mac support articles on our web site at Mac Support Articles.