The Lion installer is located in the Applications folder, and the file is named Install Mac OS X Lion. The download process from the Mac App Store also created an Install Mac OS X Lion icon in your Dock. Mac OS X 10.7 Lion First previewed at 2010’s “Back to the Mac” event, Lion was released in July 2011 as a download from the Mac App Store for $29. Lion could also.

Creating a bootable flash drive using the OS X Lion installer may seem like a difficult process, but it's a DIY task any Mac user can perform provided you have a little bit of time and this handy guide to take you through the process.

OS X Lion and its downloadable installer create a conundrum for Mac users who would like to have bootable media from which to install Lion.

The reason many people want to have a bootable Lion installer is to create clean installs: that is, to install Lion on a freshly formatted hard drive that doesn't contain any previous OS. The other major reason to want a bootable Lion installer is for emergency booting and repair of your Mac's hard drive. It's true that Lion creates a bootable Recovery partition that you can use for troubleshooting. But the Recovery partition is only usable if your drive is in basic working order. If your drive has a corrupt partition table, or you've replaced the hard drive, then the Recovery partition is downright useless.

Since we have valid reasons for wanting a bootable copy of the Lion installer, we're going to show you how to create one using a USB flash drive.

What You Need for a Bootable OS X Lion Flash Drive

• OS X Lion installer. This is available from the Mac App Store.
• 8 GB USB flash drive. You can use a larger drive if you wish, but more important than the size of the flash drive is its speed. If you're buying a new flash drive just for Lion, we recommend buying one of the fastest available. While slow (read: inexpensive) flash drives will work fine, you'll find that both the time it takes to create the bootable flash copy of the OS X Lion installer and the time it takes to install Lion on a target drive, will be somewhat long.
• Some free time. The creation time varies by the speed of the USB flash drive, but plan on 30 minutes to over an hour.

Prepare Flash Drive for OS X Lion Installer

Most flash drives don't come formatted with the native OS X file system so the flash drive you're using to create a bootable Lion installer must be erased and formatted to use the GUID Partition Table and the Mac OS X Extended (Journaled) file system.

Erase and Format Your Flash Drive

If this is a new USB flash drive, you may discover that it has been pre-formatted for use with Windows. If you've already been using the flash drive with your Mac, it may already be formatted correctly, but it's still best to erase and format the flash drive to ensure that the OS X Lion installer you copy to the flash drive will boot properly.

Warning: All data on the USB flash drive will be erased

1. Insert the USB flash drive into your Mac's USB port.
2. Launch Disk Utility, located at /Applications/Utilities.
3. In the Disk Utility window, look for the flash drive in the list of attached devices. Look for the device name, which usually appears as the drive size followed by the manufacturer's name, such as 16 GB SanDisk Cruzer. Select the drive (not the volume name, which may appear below the drive manufacturer's name), and click the Partition tab.
4. Use the Volume Scheme drop-down window to select 1 Partition.
5. Enter a name for the volume you're about to create. We prefer to use the name that Apple originally assigned to the Lion installer image that we'll copy in a later step, so we enter Mac OS X Install ESD as the volume's name.
6. Make sure the Format drop-down menu is set to Mac OS X Extended (Journaled).
7. Click the Options button, select GUID as the Partition Table type, and click OK.
8. Click the Apply button.
9. Disk Utility will display a sheet asking if you're sure you want to partition your USB flash drive. Click Partition to continue.
10. Once Disk Utility finishes formatting and partitioning the USB flash drive, quit Disk Utility.

With the USB flash drive prepared, it's time to move on to preparing and copying the OS X Lion installer image.

Copy the OS X Lion Installer Image to Your Flash Drive

The OS X Lion installer application that you downloaded from the Mac App Store includes an embedded bootable image that the application uses during the install process. In order to create our own USB flash-drive-based bootable Lion installer, we simply need to copy this embedded image to the flash drive.

We're going to use Disk Utility to clone the OS X Lion installer image to the flash drive. Because Disk Utility's cloning process must be able to see the image file, we must first copy the embedded image file to the desktop, where Disk Utility can see it without any issues.

Copy the Installer Image to the Desktop

1. Open a Finder window and navigate to /Applications/.
2. Right-click on Install OS X Lion (this is the installer you downloaded from the Mac App Store), and select Show Package Contents from the pop-up menu.
3. Open the Contents folder.
4. Open the SharedSupport Folder.
5. Within the SharedSupport Folder is an image file called InstallESD.dmg.
6. Right-click the InstallESD.dmg file and select Copy from the pop-up menu.
7. Close the Finder window.
8. Right-click in a blank area of the desktop, and select Paste Item from the pop-up menu.
9. This will create a copy of the InstallESD.dmg file on the desktop.

Clone the InstallESD.DMG File to the Flash Drive

1. Launch Disk Utility, if it's not already open.
2. Click the flash drive device (not the volume name) in the Disk Utility window.
3. Click the Restore tab.
4. Drag the InstallESD.dmg from the device list to the Source field.
5. Drag the Mac OS X Install ESD volume name from the device list to the Destination field.
6. Make sure the Erase Destination box is checked.
7. Click Restore.
8. Disk Utility will ask if you're sure you wish to perform the restore function. Click Erase to continue.
9. You may be asked for your administrator account password; supply the necessary information and click OK.
10. The clone/restore process can take a bit of time. Once the process is complete, you can quit Disk Utility.

Using the Bootable Flash Drive

To use the bootable flash drive as an OS X Lion installer, you need only do the following:

1. Insert the USB flash drive into one of your Mac's USB ports.
2. Restart your Mac.
3. When your Mac's screen turns off, hold down the option key while your Mac reboots.
4. You will be presented with the OS X Startup Manager, listing all bootable devices attached to your Mac. Use the arrow keys to select the bootable flash drive you created, and then press return or enter.
5. Your Mac will finish restarting using the flash drive. From there you can use the instructions in this step-by-step guide to complete the OS X Lion installation.

OS X Lion has just been released as a Golden Master build to developers, and provided all goes according to plan it should be slated for public release sometime later this month. Unlike with prior releases of OS X, Apple has taken a few different turns with Lion, especially in how it will be distributed to users. In addition, the system requirements for the upgrade are going to be a bit more constrained than in the past, so here is how to best prepare for the upgrade.

The first thing to do is ensure your system will run it. Any Mac that runs Snow Leopard should be able to run Lion, with the exception of the very first Intel Macs that shipped with Core Duo and Core Solo processors. These include the following systems:

1. iMac (Early 2006 and Mid 2006)
2. MacBook Pro 15-inch and 17-inch (Early 2006)
3. MacBook (Early 2006)
4. Mac Mini (Early 2006 and Late 2006)

If you have purchased your system in 2007 or later, then you should be good to go for upgrading to OS X Lion; however, you can check for the processor type on your system by going to the Apple menu, selecting 'About This Mac,' and then looking at the Processor section. If you see Core 2 Duo, Core i3, Core i5, Core i7, or Xeon in the processor name, then you should be good to go. If you only see Core Duo (without the number 2 in it), Core Solo, or any form of PowerPC, then you will not be able to run Lion.

Beyond the CPU requirements for Lion, you may also consider upgrading your RAM to at least 2GB, but preferably 4GB if possible. Macs in around 2007 to 2008 shipped with between 512MB and 2GB RAM, and Lion will require at least 2GB of memory to run adequately. You can see how much RAM is installed by going to the same About This Mac window, but consult your Mac's manual to see how much RAM you can install; some models can only upgrade to a maximum of 2GB of RAM.

Upgrading current installations

If you have a current OS X installation, unlike previous releases of OS X, Lion will not be able to upgrade from all of them; its requirement for the latest version of the Apple Store application will require you to have the latest OS X 10.6.8 version installed. This means that if you are running any version of Tiger or Leopard on an Intel Mac and wish to upgrade, then you must first purchase and install Snow Leopard, and then upgrade it.

Apple still provides OS X Snow Leopard upgrade kits for people running Tiger and Leopard, so if you have not yet upgraded to Snow Leopard and are considering the move to Lion, then now might be a good time to purchase a Snow Leopard upgrade; however, after installing it you should consider the following before immediately moving to Lion:

1. Check for PowerPC use
   Snow Leopard and prior versions of OS X have included the 'Rosetta' translator that allowed older PowerPC code to run on Intel Macs; however, this will no longer be available in Lion so be sure to check for any programs you use that are PowerPC-based, and upgrade them, find alternatives, or simply understand that they will no longer run in Lion. You can check for PowerPC applications on your system by using the System Profiler utility (see how to do this here).

2. Clear up any existing problems
   If your system is running slowly or having stability issues, you might consider addressing these before upgrading. A basic step you can take is to run a general maintenance routine, but in addition you might consider uninstalling system add-ons that you don't use, and otherwise slimming down your system. Any program that persistently runs in the background (system monitors, notification tools, and communications tools, etc.) may cause problems if they are not fully compatible with Lion.

3. Upgrade your applications
   Check for updates to any software you have running on your system, and install them if they are available. Developers will likely be releasing compatibility tweaks and updates to their software to ensure that they run in Lion, so if you use third-party utilities and programs, be sure to regularly check for updates to them in the upcoming weeks before and after Lion is released.

4. Options for running OS X 10.6.8
   Eventual upgrade to OS X 10.6.8 will be necessary in order to use its version of the App Store; however, it is not necessary to upgrade to it until you are immediately ready to install Lion. Currently people are having several prominent issues with OS X 10.6.8 that may impede on your workflow, so one option you can consider is to run in OS X 10.6.7 for now and ensure the system is running smoothly. Then when Lion is available and you are ready to upgrade, you can install the OS X 10.6.8 update followed immediately by installing Lion.

Performing clean installs

One of the most common questions surrounding Lion is whether or not users will have the option for performing a clean install on a freshly partitioned and formatted hard drive. This has been an appealing option in past versions of OS X because it gives users an excuse and a means to start fresh and to 'clean house,' so to speak.

Unfortunately Apple has released little information about the options for this, leaving people confused about whether or not if at all they will either be able to burn a boot disc of the installation media or create one out of a secondary hard drive. Recent comments from Steve Jobs suggest that a clean install will not be possible, and instead offered the option for users to use older Snow Leopard installation discs to wipe their drives, install the OS, and then upgrade to Lion. Unfortunately this will require a number of additional steps to the 'clean install' process, including the setting up Snow Leopard and subsequent updates to version 10.6.8, establishing an App Store account, and then a downloading and installing Lion.

While these added steps and requirement for using an older version of the OS is a bit of a frustration (especially since an upgrade from OS X 10.6.8 to OS X 10.7 is technically not a clean install), it may not be necessary for most people.

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Recently discussion of OS X Lion has surrounded a Recovery Partition that Lion apparently sets up on the boot drive, and whether or not that will allow for a clean setup of the OS. Apple has not officially mentioned the recovery partition option in Lion yet, but if such a partition supports a reinstall of the OS, then this coupled with Steve Jobs' recommendation would ultimately allow you to set up Lion from scratch. Here is the process one would have to take:

1. Boot to a Snow Leopard disc, partition and format the drive, and install Snow Leopard.
2. Upgrade Snow Leopard to version 10.6.8
3. Using the App Store, install Lion.

At this point the Lion installation is an upgrade installation that may not be desired; however, it will have freshly created the Lion recovery partition, so you can then continue:

4. Boot to the recovery partition (holding the Option key after hearing the boot chimes, and selecting the disk)
5. Erase the volume with OS X Lion on it
6. Install Lion freshly from the recovery partition.

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When this process is complete, the Lion installation will be a fresh and clean one. It is unfortunate that you would need to use a Snow Leopard disc for this, but you could at least be able to set up a clean installation on a freshly formatted hard drive.

It is possible that Apple will offer an option to create a separate boot disc, thumb drive, or hard drive partition on a secondary device, but because Apple is appears to be shying away from alternate boot media and has not mentioned any alternatives, we highly recommend you retain your Snow Leopard installation disc for any Mac that you are upgrading.

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