OS X Yosemite is a free download that comes to your Mac from the Mac App Store in the form of an installer that starts up automatically. If you follow the onscreen instructions, you'll end up with an upgrade install of OS X Yosemite on your startup drive. The process is quick, easy, and has a minor flaw.
Feb 12, 2019 - How to quickly make a Mac OS X bootable USB on Windows. Intending to use to reinstall Apple's OS X and click Restore with Disk Image. Dec 18, 2018 - After downloading the installer, connect the USB flash drive or other. Select Install macOS (or Install OS X) from the Utilities window, then click.
What if you want to perform a clean install, completely erasing your startup drive? Or perhaps you'd like to have the installer on a bootable USB drive, so you don’t have to keep downloading it every time you wish to upgrade one of your Macs?
The answer is you can't, at least not if you follow the onscreen instructions. The problem is that the installer is deleted as part of the upgrade process. This means you can't upgrade another Mac without downloading the installer again. It also means you don't have an easy method of performing a clean install because you don’t have a bootable copy of the installer.
To correct this basic flaw, all you need to do is quit the installer when it automatically starts up after the download is complete, and then use one of two methods for creating a bootable USB flash drive that contains the OS X Yosemite installer.
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Use Disk Utility to Create a Bootable OS X Yosemite Installer
There are two methods for creating the bootable installer. Although we prefer using a USB flash drive as the destination for the installer, you can use either method to create a bootable version of the OS X Yosemite installer on any bootable media, including hard drives, SSDs, and USB flash drives.
The first method we covered makes use of a hidden Terminal command that can perform all the heavy lifting for you, and produce a bootable copy of the installer using a single command.
There is also a manual method of performing the same process, using the Finder and Disk Utility. This article will take you through the steps to manually create a bootable copy of the OS X Yosemite installer.
What You Need
- OS X Yosemite installer. You should have already downloaded the installer from the Mac App Store. You'll find the download in the /Applications folder, with the file name Install OS X Yosemite.
- A USB flash drive or another suitable bootable device. As mentioned above, you can use a hard drive or an SSD for the bootable device, although these instructions will refer to a USB flash drive.
- A Mac that meets the minimum requirements for OS X Yosemite.
One final note: If you already installed OS X Yosemite onto your Mac, you may still wish to create a bootable copy of the installer as a troubleshooting tool, or to make additional Yosemite installations easier. In order to proceed, you'll need to re-download the Yosemite installer from the Mac App Store.
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How to Mount the OS X Yosemite Installer Image so You Can Make Copies of It
The process for creating a bootable copy of the OS X Yosemite installer follows these basic steps, which we'll describe in more detail below:
- Mount the installer on your desktop.
- Use Disk Utility to make a clone of the installer.
- Modify the clone to allow it to boot successfully.
Mount the OS X Yosemite Installer Image
Deep within the Install, OS X Yosemite Beta file that you downloaded is a disk image that contains all of the files you need to create your own bootable installer. The first step is to gain access to this image file.
- Open a Finder window and navigate to /Applications.
- Locate the file named Install OS X Yosemite.
- Right-click the OS X Yosemite file and select Show Package Contents from the pop-up menu.
- Open the Contents folder.
- Open the Shared Support folder.
- Here you will find the disk image that contains the files we need to create a bootable installer. Double-click the InstallESD.dmg file.
- This will mount the InstallESD image on your Mac's desktop and open a Finder window that displays the contents of the mounted file.
- You may notice that the mounted image seems to contain only a single folder, named Packages. In actuality, there's an entire bootable system on the image file that is hidden. We need to use Terminal to make the system files visible. If you don't know how to do this, you can use the instructions in the article below to make the files visible: View Hidden Folders on Your Mac Using Terminal.
- When you've done that, we can continue.
- Now that the files are visible, you can see that the OS X Install ESD image contains three additional files: .DS_Store, BaseSystem.chunklist, and BaseSystem.dmg. We're going to use this Finder window in subsequent steps, so leave this window open.
With all the files we need now visible, we can move on to using Disk Utility to create a clone of the OS X Install ESD image that we mounted on the desktop.
![Usb Usb](/uploads/1/2/4/2/124227044/827632149.jpg)
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Use Disk Utility's Restore Feature to Clone the OS X Install ESD Image
The next step in the creation of a bootable copy of the OS X Yosemite installer is to use Disk Utility's Restore capabilities to create a clone of the OS X Install ESD image you mounted on your desktop.
- Launch Disk Utility, located at /Applications/Utilities.
- Make sure the target USB flash drive is connected to your Mac.
- Select the BaseSystem.dmg item listed in the left-hand pane of the Disk Utility window. It may be listed near the bottom, after your Mac's internal and external drives. If the BaseSystem.dmg item is not present in the Disk Utility sidebar, you can drag it there from the Finder window that appeared when you mounted the InstallESD.dmg file. Once the file is present in the Disk Utility sidebar, be sure to select BaseSystem.dmg, not InstallESD.dmg, which will also be in the list.
- Click the Restore tab.
- In the Restore tab, you should see BaseSystem.dmg listed in the Source field. If not, drag the BaseSystem.dmg item from the left-hand pane to the Source field.
- Drag the USB flash drive from the left-hand pane to the Destination field.
- The next step will completely erase the contents of the USB flash drive (or any other bootable device you dragged to the Destination field).
- Click the Restore button.
- You'll be asked if you're sure you want to erase the USB flash drive and replace its contents with BaseSystem.dmg. Click the Erase button.
- If requested, supply your administrative password and click OK.
- The restore process will take a bit of time. Once it's complete, the Flash drive will mount on your desktop and open in a Finder window named OS X Base System. Keep this Finder window open, because we'll be making use of it in subsequent steps.
We're done with Disk Utility, so you can quit this app. All that's left to do is modify the OS X Base System (the flash drive) to make the OS X Yosemite installer work correctly from a bootable device.
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The Final Step: Modify the OS X Base System on the Flash Drive
So far, we found the hidden image file within the Yosemite installer. We created a clone of the hidden image file, and now we're ready to copy a couple of files that will make the bootable version of the OS X Yosemite installer work correctly.
We're going to be working in the Finder, with the two windows we asked you to keep open during the previous steps. It can get a bit confusing, so read through the following steps first, to make sure you understand the process.
Modify the OS X Base System on Your Flash Drive
- In the Finder window named OS X Base System:
- Open the System folder.
- Open the Installation folder.
- Within this folder, you'll find an alias named Packages. Delete the Packages alias by dragging it to the trash, or by right-clicking the alias and selecting Move to Trash from the pop-up menu.
- Leave the Installation window open, because we'll use it below.
- Open the Finder window named OS X Install ESD. (If you didn't leave this window open from the earlier steps, follow the instructions in Step 2 to bring the window back.)
- From the OS X Install ESD window, drag the Packages folder to the Installation window you left open above.
- From the OS X Install ESD window, drag the BaseSystem.chunklist and BaseSystem.dmg files to the OS X Base System window (the root level of the USB flash drive) to copy them to the flash drive.
- Once the copying is complete, you can close all of the Finder windows.
There's one last step. Earlier, we made invisible files and folders visible. It's time to return those items to their original invisible state.
Your USB flash drive is now ready to be used as a bootable OS X Yosemite installer.
You can boot from the Yosemite installer you just made by inserting the USB flash drive into your Mac, and then starting your Mac while holding down the option key. This will present the Apple boot manager, which will let you select the device you wish to start up from.
A bootable copy of OS X or macOS on a USB flash drive is a great emergency backup tool to have on hand. It allows you to be ready to go almost immediately should anything happen to your existing startup drive.
Why a flash drive? A bootable external or internal hard drive works well for desktop Macs but presents a cumbersome problem for notebook Macs. A flash drive is a simple, inexpensive, and portable emergency boot device that can handle OS X or the macOS. Heck, it can even have both operating systems installed, letting you use the emergency USB flash drive to boot any of the Mac's you may have. Even if you don’t use a notebook, you may want to have a bootable USB flash drive on hand.
What You Will Need
- An Intel-based Macintosh
- An install DVD of OS X 10.5 (Leopard), OS X 10.6 (Snow Leopard) or the downloaded installer image of OS X 10.7 or later or macOS Sierra and later.
- A 16 GB or larger USB flash drive
We’ve chosen to use a 16 GB or larger flash drive as a minimum for two reasons. First, a 16 GB flash drive is large enough to accommodate the current minimum amount of space required to install OS X directly from the install DVD, or macOS from a download from the Mac app store, or from the Recovery HD.
Eliminating the need to pare down the OS to get it to fit on the USB flash drive significantly simplifies the installation process. Second, the cost of USB flash drives is falling. A 16 GB USB flash drive is large enough to install both a complete copy of the macOS and some of your favorite applications or recovery utilities, making it a budget-friendly emergency device that can boot your Mac and possibly repair or recover its data and get it running again.
Using a larger flash drive can allow you to install multiple versions of the Mac operating system, or include additional utilities and apps you feel would meet your needs in an emergency. We've used a 64 GB flash drive divided into two 32 GB partitions to allow us to install OS X Yosemite and macOS Sierra which is the two Mac OS's used on our Mac's here at home.
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Selecting a USB Flash Drive for Booting Your Mac
Selecting a USB flash drive to use for creating a bootable OS X or macOS device is actually relatively straightforward, but here are some concerns to consider and a few suggestions to make the selection process easier.
Compatibility
The good news is that we haven’t come across any USB flash drives that are not compatible for this purpose. If you check the specifications of USB flash drives, you may notice that they sometimes don’t mention Macs, but fear not. All USB-based flash drives use a common interface and protocol to ensure compatibility; Mac OS and Intel-based Macs follow these same standards.
Size
It’s possible to install a bootable copy of OS X on USB flash drives smaller than 8 GB, but it requires fiddling around with OS X’s individual components and packages, removing the packages you don’t need, and paring down some of OS X’s capabilities.
For this article, we’re going to forego the extra steps and all that fiddling, and instead install a fully functional copy of OS X onto a USB flash drive. We recommend a 16 GB or larger flash drive because it’s big enough to install a complete copy of OS X, with room to spare for a few applications.
This is also true of macOS, the later versions of the Mac operating system. 16 GB is really the smallest size flash drive you should consider, and like just like most storage issues, bigger is better.
Speed
Speed is a mixed bag for USB flash drives. In general, they’re pretty speedy at reading data but they can be agonizingly slow at writing it. Our primary purpose for the USB flash drive is to serve as an emergency boot and data recovery drive, so we’re most concerned with read speed. Focus on read speeds rather than write speeds when you shop for a USB flash drive. And don’t be alarmed when it takes longer than normal to install the Mac OS, because you will be writing lots of data.
Type
USB flash drives are available in multiple flavors of the USB interface. While the standards tend to change over time, currently USB 2 and USB 3 are the two common interface types. Both will work with your Mac, but if your Mac has USB 3.0 ports (most Macs since 2012 have USB 3 ports), you will want to use a flash drive with USB 3 support for the faster read and write speeds available.
If you're using a MacBook with USB 3-C ports, you will likely need an adapter to go between USB 3-C and USB 3. Apple is the primary source for this type of adapter, but as USB-C gains popularity, you will be able to find third party suppliers at reasonable prices for the adapters.
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Format Your USB Flash Drive for Use with the Mac
Most USB flash drives are formatted for use with Windows. Before you can install OS X on a USB flash drive, you will need to change the drive’s formatting to the standard used by OS X (Mac OS X Extended Journaled).
Format Your USB Flash Drive
- Insert the USB flash drive into your Mac’s USB port.
- Launch Disk Utility, located at /Applications/Utilities/.
- In the list of drives attached to your Mac, select the USB flash drive device. In our case, it’s called 14.9 GB SanDisk Cruzer Media. (Like lumber, hard drives and flash drives are actually slightly smaller than their specs would have you believe.)
- Click the Partition tab.
- Select 1 Partition from the Volume Scheme drop-down menu.
- Enter a descriptive name for your flash drive; we chose Boot Tools.
- Select Mac OS X Extended (Journaled) from the Format drop-down menu.
- Click the Options button.
- Select GUID Partition Table from the list of available partition schemes.
- Click OK.
- Click the Apply button.
- A sheet will drop down, warning you that you are about to erase all data from the disk. Click Partition.
- Disk Utility will format and partition your flash drive.
- Quit Disk Utility.
If you're using OS X El Capitan or later you may notice that Disk Utility looks and operates a bit different. The process for formatting your flash drive is very similar to what is outlined above.
Enable Ownership of Your USB Flash Drive
In order for a drive to be bootable, it must support ownership, which is the ability of files and folders to have specific ownership and permissions.
- Locate the USB flash drive on your Mac desktop, right-click its icon, and select Get Info from the pop-up menu.
- In the Info window that opens, expand the Sharing & Permissions section, if it’s not already expanded.
- Click the lock icon in the bottom right corner.
- Enter your administrator password when asked.
- Remove the check mark from Ignore ownership on this volume.
- Close the Info panel.
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Install OS X or macOS on Your USB Flash Drive
Once you complete the previous step, your USB flash drive will be ready for you to install OS X.
Install OS X
We prepared the USB flash drive by partitioning and formatting it and then enabling ownership. The flash drive will now appear to the OS X installer as just another hard drive that is ready for installation of OS X. Because of our preparation, the steps for installing OS X will be no different than a standard OS X installation.
Having said that, we recommend that you customize the software packages that OS X will install. Because of the limited space on the USB flash drive, you will need to remove any printer drivers that you don’t use, as well as all of the extra language support that OS X installs. Don’t worry if this sounds complicated; the installation instructions we link to here are step-by-step guides and they include information on customizing software packages.
Before you begin the installation, a few notes about the process. As we mentioned earlier, USB flash drives are much slower at writing data. Since the installation process is all about writing data to the USB flash drive, it’s going to take quite some time. When we performed the installation, it took about two hours. So be patient, and don’t worry about how slow some of the processes seem; this is normal. You can expect to see plenty of beach balls and slow responses as you work your way through the installation process.
Ready to install? Click the link below for your OS and follow the step-by-step guide.
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Using a USB Flash Drive as a Startup Volume
Now that you have installed OS X on your USB flash drive, you’ve probably noticed how slow it seems. This is normal for flash-based drives, and there’s not much you can do about it, except to buy the fastest USB flash drive in your price range.
If speed is a big issue for you, you can entertain the idea of purchasing a small SSD in a portable enclosure. Some manufacturers are making SSDs that are just slightly larger than the standard flash drive. Of course, you will pay a premium for the speed.
It’s important to remember why you’re creating this startup drive. It’s for use in an emergency, when your Mac won’t boot, either because of a hard drive problem or a software-related problem. A bootable USB flash drive will help you get your Mac back to working condition, by letting you use all of the tools a fully-working Mac has available.
In addition to being able to use Disk Utility, the Finder, and Terminal, and have access to the Internet, you can also load some specific emergency tools onto your USB flash drive. Here are some of the utilities we suggest installing. You don’t need to have all of them; in fact, it’s unlikely they would all fit onto the flash drive after you install OS X, but having one or two certainly makes sense.
Emergency Utilities
- Data Rescue for data recovery.
- DiskWarrior for data recovery, disk testing, and disk repair.
- Drive Genius for disk repair, defragmenting, partitioning, copying, and other useful tools.
- TechTool Pro for memory testing, drive testing, data recovery, and Mac hardware testing.