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Booting the USB Installer

  1. Insert the USB flash drive into your Mac. 

  2. Restart your Mac while holding down the option key.

  3. After a short delay, your Mac will display the OS X Startup Manager, which will display all of your bootable devices. 

  4. Use your Mac's arrow keys to select the Mac OS X installer you want to use, and then press the enter or return key.

  5. Your Mac will start up from the USB flash drive that contains the installer. About 3 minutes with Lexar 16GB Flash Drive

  6. Your Mac will then display the OS X Utilities window - From here you can perform a Clean Install, reinstall, upgrade or use as recovery disk

Installer hiccups

First, the Apple installer's progress bar is not accurate. Depending on your mac hardware an installation can take from 25 minutes to a couple hours to complete. Any errors that pop up do not really tell you what happened. Best advice is to try again. Here are a few of the most common things you may encounter.


Installer stuck on

'About a second remaining'

Try an be patient , let it run as long as you can stand to.

The progress bar you see is just a poor inaccurate guess at how long it will take. Wait a little longer, I've seen it take 45 minutes to an hour in some cases. Slower, older hard drives take longer, this is where having a SSD helps.

Error installer can't be verified. May have been corrupted....

Most common on El Capitan or Yosemite

The installer is not corrupt, Apple made changes in Feb 2016 to their authentication certificates. Change the date on your computer and try the install again.  See troubleshooting


Any mac that had previous power or battery issues, major board replacement or has general power (SMC) issues seem to have the "date" issue and more problems with installs.


Hardware issues such as bad RAM memory will also cause errors at startup. Don't forget to use the Disk Utility to check your hard drive before installation.

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