How to Make a Bootable macOS Sierra USB Install Drive

The easiest way to create a USB flash installer is with the free program, Disk Creator.

Install macOS Sierra Using Bootable USB Flash Drive

To perform a clean installation of macOS Sierra (basically, Mac OS X 10.12), I recommend using a bootable USB flash drive containing the macOS Sierra installer. Below are the steps I took to create the bootable USB flash drive and how I used it to install macOS Sierra.

Note: The macOS Sierra Disk Utility and installer appears to be more buggy and much slower than previous versions. The best advice for installing macOS Sierra is to try again and be very patient (if you expect an operation to complete in 5 minutes, then give it at least 50 minutes).

Download macOS Sierra Installer

The macOS Sierra installer is available from the Mac App Store. Run the “App Store” application, search for “macOS Sierra”, and download it. It will save the installer as an “/Applications/Install macOS Sierra.app” file (about 4.97GB in size).

Note: If you run the macOS Sierra installer to upgrade your Mac, the downloaded file will be deleted automatically after the upgrade is completed. To keep that file, you will want to move it out of the Applications folder so it won’t be deleted after an upgrade. Launch the “Terminal” application and run this command to move the downloaded installer to your user’s “Downloads” folder:

sudo mv / Applications / Install\ macOS\ Sierra.app / ~ / Downloads /

If you are paranoid (doesn’t hurt), you can verify that the installer file was downloaded correctly by verify its checksum. Run the “Terminal” application and this command:

hdiutil verify / Applications / Install\ macOS\ Sierra.app / Contents / SharedSupport / InstallESD.dmg

# If successful, the last output line should read:
# hdiutil: verify: checksum of “/Applications/Install macOS Sierra.app/Contents/SharedSupport/InstallESD.dmg” is VALID

Format USB Flash Drive

The macOS Sierra installer takes up 5.1GB of space on the USB flash drive, so you will need a flash drive with a capacity of 8GB or greater.

Note: If the flash drive is mounted under “/Volumes” successfully when you plug it in, you can skip the following steps to reformat the flash drive. This is because the script we run to create the bootable drive will reformat the flash drive as an initial step. Because I am paranoid, I recommend reformatting the USB flash drive manually anyhow.

Format the USB flash drive using these steps:

Plug the USB flash drive into your Mac.
Launch the “Disk Utility” application.
On the left-hand pane, select the USB drive (not the partition under it, if any).
Click on the “Erase” tab (or button at the top).
1. Input a name like “Sierra” (this name will be overwritten later).
2. Select “Mac OS Extended (Journaled)” for “Format”.
3. Select “Master Boot Record” for “Scheme”.
4. Click the “Erase…” button at the bottom. Click the “Erase” button in the warning popup dialog if you get one.
  - The format operation may take several minutes to complete. (USB 2.0 and large capacity drives will take longer.) After the format completes, the partition will be mounted under “/Volumes/Sierra” (or whatever name you selected above).
  - Note: Under macOS Sierra, the Erase function will fail if the USB drive’s partition is mounted. You can manually unmount the partition before running Erase. Or you can run Erase twice; the first time will unmount the partition and fail, and the second time will actually do the format (which will succeed).
# The –volume value is the mounted USB flash drive partition; in this case, named /Volumes/Sierra

sudo / Applications / Install\ macOS\ Sierra.app / Contents / Resources / createinstallmedia –volume / Volumes / Sierra –applicationpath / Applications / Install\ macOS\ Sierra.app –nointeraction

# You will be prompted for your user’s administrative password.

Update: For macOS 10.14 Mojave (and its predecessor, macOS 10.13 High Sierra), the createinstallmedia command no longer requires the “–applicationpath” and “–nointeraction” flags, so omit them. The command becomes just “createinstallmedia –volume /Volumes/Mojave”. Note: If the createinstallmedia command returns a “Failed to start erase of disk due to error (-9999, 0)” error, then your current Mac OS X version does not fully support the createinstallmedia tool. Instead, create the USB installation drive manually using instructions from Bootable USB Flash Drive to Install Mac OS X 10.10 Yosemite. The “createinstallmedia” program will erase the USB flash drive, create a new partition named “Install macOS Sierra”, and copy the installation files to that partition. The output will look like:

Erasing Disk: 0 % . 10 % . 20 % . 30 % . 100 % .
Copying installer files to disk.
Copy complete.
Making disk bootable.
Copying boot files.
Copy complete.
Done.
1. Shutdown the Mac.
2. Insert the USB flash drive.
3. While holding the “option/alt” key down, turn on the Mac to display the boot Startup Manager.
4. You should see one or more icons, one of which should be called “Install macOS Sierra” for the USB flash drive. (The internal hard drive may not be visible if it does not have a valid, bootable partition installed.)
  - Note: If you don’t see the USB flash drive’s “Install macOS Sierra”, try removing and re-inserting the USB flash drive while viewing the Startup Manager screen. The USB flash drive should then appear after a few seconds.
5. Select the “Install macOS Sierra” (with left/right arrow keys) and hit the “return/enter” key to boot from the USB flash drive.
1. Click on the “Disk Utility” option and click the “Continue” button on the bottom to launch the “Disk Utility” application.
2. On the left-hand pane, select the hard drive (not the partition under it, if any).
3. Click on the “Erase” button at the top.
  1. Input a name like “macOS”.
  2. Select “Mac OS Extended (Journaled)” for “Format”.
  3. Select “GUID Partition Map” for “Scheme”.
  4. Click the “Erase…” button at the bottom.
    - For SSD (Solid State Drive), the format operation may take less than a minute to complete. For mechanical hard drive, it may several minutes to hours, depending upon the size, speed, and condition of your hard drive.
    - Note: Again, the Erase function will fail if the hard drive’s partition is mounted. You can manually unmount the partition before running Erase. Or you can run Erase twice; the first time will unmount the partition and fail, and the second time will actually do the format (which will succeed).
  1. Click on the “Install macOS” option and click the “Continue” button.
  2. The “macOS Sierra” installer’s splash screen will appear. Click the “Continue” button.
  3. Click on the “Agree” button to agree to the license. A popup confirmation window will appear; click on the popup’s “Agree” button.
  4. Select the hard drive and click the “Install” button.
  - Reset your Mac by doing the following:
    1. Reset the SMC (see step 3 under the “Reset the SMC on Mac notebook computers” section).
    2. Reset the NVRAM (aka PRAM).
    3. Run the Apple Hardware Diagnostic or Test to make sure you don’t have a hardware failure.
    4. Finally, retry the macOS Sierra install.
  - Use a different USB port on the Mac.
  - Use another brand of USB flash drive.
  - Delete and re-download the macOS Sierra installer (especially if you downloaded it a long while ago). Even if the checksum is okay, you may want to re-download in case there is a newer version of the installer with a bug fix for your very problem.
  - Download an older Mac OS X version, say Mac OS X 10.11 El Capitan, install that, and then upgrade to macOS Sierra. If you know the Mac OS X version which came with your Mac originally, consider downloading (if you still have access) and installing that version first.
  - Use the Mac Recovery System to download and install the original OS version that came with your Mac. Then upgrade from that to macOS Sierra.
  - Buy a more recent model Mac (at most a couple of years old). It may be that your current Mac is too old or slow to support macOS Sierra. It’s okay to keep running an old Mac OS version. (For example, if I had a Core 2 Duo Mac, I would not run anything later than Mac OS X 10.9 Mavericks on it.)
  - I can’t create a bootable OSX Mavericks Install USB Drive
  - How to create a bootable installer for macOS Sierra
  How to Make a Bootable macOS Sierra USB Install Drive
  
  The easiest way to create a USB flash installer is with the free program, Disk Creator.
  1. Download the macOS Sierra installer and Disk Creator .
  2. Insert an 8GB (or larger) flash drive. If you have any other data on that flash drive, back it up now, because the installer will delete everything on it.
  3. Open Disc Creator and click the “Select the OS X Installer” button.
  4. Find the Sierra installer file. This is should be located in your Applications folder.
  5. Select your flash drive from the drop-down menu.
  6. Click “Create Installer.”
  When it’s done, insert your USB drive into any Mac, then launch the installer by holding down the Option key when you boot up your computer.
  
  The DIY Option: Terminal
  
  If you don’t want to download an extra bit of software, you can make your own installer USB drive using Terminal.
  1. Download the macOS Sierra installer .
  2. Insert an 8GB (or larger) flash drive and give it a name. For this tutorial, we’ll use the name Untitled . Make sure the drive is formatted for OS X Extended (Journaled). If it isn’t, open up Disk Utility and format is so it is. Before you do so, back up any important data on that drive. It’s best to disconnect any other external hard drives or flash drives so you don’t mix them up.
  3. Open up Terminal (Applications > Utilities).
  4. Type (or copy and paste) this command into Terminal, replacing Untitled with the name of your drive, then press Enter: sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia –volume /Volumes/Untitled –applicationpath /Applications/Install\ macOS\ Sierra.app –nointeraction &&say Done
  5. Type in your password when prompted and press Enter.
  6. Let the command line do its work and don’t interrupt it until you see the final line that says Done . This can take a while, so be patient.
  When it’s done, insert your USB drive into any Mac, then launch the installer by holding down the Option key when you boot up your computer.
  Related posts:

How to Make a Bootable macOS Sierra USB Install Drive

Install macOS Sierra Using Bootable USB Flash Drive

How to Make a Bootable macOS Sierra USB Install Drive

The DIY Option: Terminal

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