How to Make a Boot Disk for Mac OS X

Use the following steps to install your Mac operating system from a USB.

1. Connect the bootable USB drive to your machine.
2. Start the computer and hold down the Options key until you hear the chime.
3. Choose USB Installer and then Disk Utility.
4. Select the main drive from the top of the left panel.
5. Click the Erase button from the top menu.
6. Select the Format drop-down list and choose Mac OS X Extended (Journaled).
7. Click Erase to erase all data from the selected drive and format it for use.
8. Close Disk Utility when formatting is complete.
9. Choose Install OS X from the menu and select your main drive as the target.

You can get your Mac to boot from a USB drive with these steps:

1. Connect the USB stick to your Mac.
2. Power on the computer and hold down the Option key until you hear the chime.
3. Release the Option key and wait for the boot options to be displayed.
4. Select the device USB stick as the device that will be used to boot the Mac.

To get to the boot menu on a MacBook Pro, use these steps:

1. Power off the MacBook.
2. Connect the device that will be used to boot the laptop.
3. Power on the MacBook and hold down the Option key until you hear the chime.
4. Release the Option key and wait for the boot options to be displayed.
5. Select the device you want to use to boot the MacBook.

Use this procedure to make a USB stick bootable with Disk Drill:

1. Download, install and launch Disk Drill.
2. Connect a USB stick to your Mac.
3. Select Create Boot Drive and choose the source and target volumes.
4. Allow the process to complete.

Use these steps to see if a USB drive is bootable:

1. Connect the drive to your Mac.
2. Start Disk Utility.
3. Select the USB Drive and click Info.
4. Scroll down to the Bootable field which will tell you if the device is bootable.

There are multiple reasons that a USB drive may not be bootable including:

• It may be corrupt;
• The drive may be incompatible with your OS;
• The Startup Security Utility setting may prevent it from booting;
• Manual intervention is needed if Option ROM Firmware is on the USB drive.

UEFI is the advanced replacement for BIOS that is used on Macs with Intel-based CPUs.  Accessing UEFI mode on a Mac requires you to execute this command as your machine starts up.

• Start your Mac and press and hold CMD, OPT, “O” and “F”.

From within the EFI, you can select the USB bootable disk as the volume to start your computer.

You can easily make a bootable USB drive with the help of the following software applications:

1. Rufus
2. UNetbootin
3. balenaEtcher