Creating A Mac Startup Disk For Os X

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Launch Disk Utility (in /Applications/Utilities) and then drag BaseSystem.dmg (in the OS X Install ESD volume) into Disk Utility’s left-hand sidebar. Select BaseSystem.dmg in Disk Utility’s.

Create Mac Startup Disk

There are various ways to boot macOS. Aside from using the built-in Startup Manager, you can also boot into Verbose, Safe, and Target Disk modes. In addition to this, macOS users also have an option of picking a disk to boot the operating system from. But let’s delve into something more specific. You’re about to find out how to boot your Mac up directly from external storage, specifically flash storage or a USB-based flash drive. Learn how to create bootable flash drive for Windows 10.

Why You Need to Boot from External Drive?

There are many occasions you may have trouble with your Mac.

  • Corrupted system files and Mac crashes unexpectedly.
  • Mac runs very slow with sufficient storage.
  • You have deleted some system files wrongly.
  • You couldn’t login to your Mac.
  • Troubleshooting purposes.

Let’s begin with the obvious question here; what are the basic requirements for creating bootable USB for Mac?

How to Create Bootable USB Drive for Mac?

  1. USB drive with sufficient storage space.
  2. Access to a working and supported Mac.
  3. Format USB to Apple supported file system.
  4. Get installer file for macOS.
  5. Create bootable USB.
  6. Booting Mac from Startup Manager.

If you are not able to login to your Mac, you need to use Time Machine backup disk. Otherwise you should have another Mac for creating a bootable USB.

1. USB Drive

The macOS installer file is large with approximate size of 6 to 10GB depending upon the version. Also the process needs to sufficient storage space on your USB. So ensure to have at least 32GB or greater storage space on your USB drive.

Remember to copy and backup the USB since you need to delete the entire content for creating the bootable drive.

2. An Intel Based Mac

Apple transitioned to an Intel processors in 2005. In other words, if your Mac is not older than 2005, you should be fine.

3. Format USB Flash Drive to Apple File System

First, plug in your USB drive. Press “Command +Spacebar” to access Spotlight, then type “Disk Utility”. You can view the current file system of the USB drive. In our example, we have FAT32 file system which is compatible on Windows. You need to erase and format the USB to be compatible with your Mac.

Click on the “Erase” button on “Disk Utility” and choose the format as either APFS or Mac OS Extended. In most cases, your Mac will show the supported format by default and you don’t need to change it. On older Mac, you will see an additional scheme option, choose “GUID Partition Map”. Click on “Erase” button to continue further.

Disk Utility will delete all content on the USB and format it in the selected APFS or Mac OS Extended format.

4. MacOS Installer File

In order to create a bootable USB drive for Mac, you need download Mac OS installer. Open App Store on your Mac and search for the latest macOS version. Remember, App Store will only have the latest version which is macOS Mojave at this point when we write this article. Search for “macOS mojave” and click on the “Get” button.

Mac

This will start downloading the installer file to your “Applications” folder.

5. Creating USB Installer

After downloading, the installer will automatically ask you to install macOS Mojave. Simply quit the installer without starting the installation.

  • At this point, ensure you have inserted the formatted USB drive, let’s say the name of the USB volume is “Boot Disk”.
  • Also make sure the downloaded macOS installer file is in “Applications” folder.
  • Press “Command + Spacebar” and search for “terminal” to open Terminal app.
  • Copy and paste the below command in Terminal and hit enter.
  • You need to enter admin password to proceed further.
  • Terminal will ask you to confirm erasing the volume, press Y and hit enter to confirm.

Ready to start.

How To Create A Startup Disk For Mac Os X Mountain Lion

To continue we need to erase the volume at /Volumes/Boot Disk.

If you wish to continue type (Y) then press return:

  • Now the erase disk process will start to copy the installer file on the USB drive. After successful completion of the process, name of the USB drive will be changed similar to the installer file name like “Install macOS Mojave”.

Note that Apple discourages booting with an earlier macOS version than the version your device is shipped with.

6. Boot Mac from USB

Follow the below process to boot your Mac from bootable USB:

  • Insert the bootable USB installer drive and go to “Apple Menu > Restart”.
  • When your Mac restarts, press and hold the Option key till “Startup Manager” opens.
  • The Startup Manager scans and lists the drives that are connected and bootable.
  • Note that the Startup Manager will only list volumes that include bootable volumes. If you only see “Macintosh HD” like below then the USB drive is not connected to your Mac or not created properly with the installer file.
  • Select your Wi-Fi network name from the “Choose Network…” dropdown and enter the password to connect to internet. Remember, you need to have an internet connection for installing from USB as the installer needs to get updates for your Mac from Apple’s server.
  • Double click on your USB that contains the macOS installer or highlight it and press the return key.
  • You will see macOS Recovery app and choose “Install macOS” option from Utilities.
  • It may take long time depending upon your Mac to start booting with macOS Mojave.

Wrapping Up

As simple as the process seems, it tells you a lot about your system. For example, if a USB flash drive that contains a bootable copy of macOS doesn’t show up on the Startup manager, you may need to repair the disk permission. Also, remember to format the USB drive with a APFS or Mac OS Extended format.

That said, now you know how to boot up another version of or a copy of macOS and troubleshoot possible issues with your device.

These advanced steps are primarily for system administrators and others who are familiar with the command line. You don't need a bootable installer to upgrade macOS or reinstall macOS, but it can be useful when you want to install on multiple computers without downloading the installer each time.

Download macOS

Find the appropriate download link in the upgrade instructions for each macOS version:

macOS Catalina, macOS MojaveormacOS High Sierra
Installers for each of these macOS versions download directly to your Applications folder as an app named Install macOS Catalina, Install macOS Mojave, or Install macOS High Sierra. If the installer opens after downloading, quit it without continuing installation. Important: To get the correct installer, download from a Mac that is using macOS Sierra 10.12.5 or later, or El Capitan 10.11.6. Enterprise administrators, please download from Apple, not a locally hosted software-update server.

OS X El Capitan
El Capitan downloads as a disk image. On a Mac that is compatible with El Capitan, open the disk image and run the installer within, named InstallMacOSX.pkg. It installs an app named Install OS X El Capitan into your Applications folder. You will create the bootable installer from this app, not from the disk image or .pkg installer.

Use the 'createinstallmedia' command in Terminal

  1. Connect the USB flash drive or other volume that you're using for the bootable installer. Make sure that it has at least 12GB of available storage and is formatted as Mac OS Extended.
  2. Open Terminal, which is in the Utilities folder of your Applications folder.
  3. Type or paste one of the following commands in Terminal. These assume that the installer is still in your Applications folder, and MyVolume is the name of the USB flash drive or other volume you're using. If it has a different name, replace MyVolume in these commands with the name of your volume.
    Catalina:*
    Mojave:*

    High Sierra:*
    El Capitan:
  4. Press Return after typing the command.
  5. When prompted, type your administrator password and press Return again. Terminal doesn't show any characters as you type your password.
  6. When prompted, type Y to confirm that you want to erase the volume, then press Return. Terminal shows the progress as the bootable installer is created.
  7. When Terminal says that it's done, the volume will have the same name as the installer you downloaded, such as Install macOS Catalina. You can now quit Terminal and eject the volume.

* If your Mac is using macOS Sierra or earlier, include the --applicationpath argument, similar to the way this argument is used in the command for El Capitan.

Use the bootable installer

After creating the bootable installer, follow these steps to use it:

  1. Plug the bootable installer into a compatible Mac.
  2. Use Startup Manager or Startup Disk preferences to select the bootable installer as the startup disk, then start up from it. Your Mac will start up to macOS Recovery.
    Learn about selecting a startup disk, including what to do if your Mac doesn't start up from it.
  3. Choose your language, if prompted.
  4. A bootable installer doesn't download macOS from the Internet, but it does require the Internet to get information specific to your Mac model, such as firmware updates. If you need to connect to a Wi-Fi network, use the Wi-Fi menu in the menu bar.
  5. Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the onscreen instructions.

Learn more

For more information about the createinstallmedia command and the arguments that you can use with it, make sure that the macOS installer is in your Applications folder, then enter this path in Terminal:

Catalina:

Mojave:

High Sierra:

El Capitan: