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With genuine Lion install media being a rarety (and only included on certain newer Macs), there are a lot of queries by users on how they are best able to re-install (or even simply install) Lion on their computers.

I think it would be very useful to have a single canonical answer that is able to present every sensible install option on a single page, from which machines include the USB install media to how to use Internet Recovery, and all the homebrew options of self burning an image to DVD etc inbetween.

So, what methods are you aware of, or have you used, to re-install Lion on your Mac?

Please try to include 1 answer per answer, and detail it as fully as possible in order to prevent duplicate answers, or answers that contain bits of the method etc. Feel free to edit others answers to increase the detail level. Try not to link to existing guides or external webpages without summarising or paraphasing, it is far better to include the information directly on this site.

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Restoring iLife: On a Mac that came shipped with Lion, you can simply re-download iLife from the Mac App Store after signing in with your Apple ID. –  gentmatt Apr 2 '12 at 10:03

8 Answers 8

Create a bootable OS X Lion USB stick or DVD based on the Mac App Store download

  1. Buy and download Lion from the Mac App Store. The installer should show up in your Applications folder.
  2. Right-click on the installer and hit “Show Package Contents”. Navigate to Contents/SharedSupport and look for a file called InstallESD.dmg.
  3. Open up Disk Utility and drag the DMG file into the left-hand sidebar. If you’re burning it to a DVD, insert your DVD, select the disk image in the sidebar, and hit the “Burn” button. Skip down to the last step to use it.
  4. If you want to burn Lion to a USB flash drive, plug it in and click on it in the left-hand sidebar in Disk Utility. Go to the Partition tab and select “1 Partition” from the dropdown menu. Choose “Mac OS Extended (Journaled)” on the left.
  5. Hit the “Options” button under the partition table and choose “GUID Partition Table”. You’ll need this to make the drive bootable on a Mac. Hit the “Apply” button when you’re done to format your drive (note: it will erase everything on the drive).
  6. Click on the “Restore” tab, choose the InstallESD.dmg file as the source and your flash drive as the destination. Hit the “Apply” button and it will create your bootable USB drive.

  7. Reboot into OS X and hold the option key when you hear the startup chime. You can boot into your DVD or flash drive from there.

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Lion Recovery (requires internet connection)

Reinstalling OS X Lion via Lion Recovery requires broadband access to the Internet via Wi-Fi or an Ethernet connection. OS X Lion is downloaded over the Internet from Apple when Lion Recovery is used for reinstallation.

The OS X Lion download is about 4 GB large. [source]

  • Upon boot you can hold +R in order to directly boot into the recovery partition. The recovery partition exists on every Mac that came shipped with Lion or had Lion installed as a clean install.
  • Upon boot you can hold . This will display all options of where your Mac can boot from. Choose Recovery HD.
  • Apples offers the Lion Recovery Disk Assistant to create your own Lion install USB. Using this method, an install of Lion requires an internet connection. Upon boot you hold and choose the recovery disk.

Once your Mac has booted from the recovery partition/usb you may have to pass a setup for your language preferences first. After that choose to install Lion from the menubar.

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Upgrade install (from Snow Leopard)

You can download the Lion from the Mac App store. This will install Lion after a reboot. Your applications and personal data will not be removed. But you should perform a backup before the upgrade.

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Buy a bootable OS X Lion USB stick

You can buy a bootable OS X Lion USB Thumb Drive from the Apple Store: http://store.apple.com/us/product/MD256Z/A

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Use Lion Recovery Disk Assistant

A third way is to download the Lion Recovery Disk Assistant which is 1MB in size and will preform the upgrade to Lion. For this option, an existing Recovery HD and an external hard drive is needed and what is does is the following: reinstall Lion, repair the disk using Disk Utility, restore from a Time Machine backup.

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Using TimeMachine backup

I only realised recently, but if you have used Time Machine on a mac with Lion, the restoring partition is also copied on the drive. So you can simply choose to boot from the TM backup drive, and install lion from there. The restoring partition is moved on the internal drive, and then installing is the same with other procedures .

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Make a bootable Lion install disc or drive

As you may have noticed, Lion is the first OS which doesn't ship on a bootable disk. So in order to get one, you need to create this disk.

Basically, it comes down to donwloading Lion in the Mac App Store and burn it on a disk, put it on a flash drive.
You can find and extensive tutorial over here.

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Ah, bummer, too late I see. –  Michiel Apr 2 '12 at 9:35
    
Not too late to improve., the other answers need splitting out - 1 method per answer, and you can still get busy increasing details - screenshots, commentary, gotchas etc. –  stuffe Apr 2 '12 at 9:37
    
So, you want just one method per answer? –  Michiel Apr 2 '12 at 9:39
    
Yes, that way each answer is canonical, and there is no duplication. Anyone can then improve an existing one without worrying about treading on toes. –  stuffe Apr 2 '12 at 9:40
    
Ok, I'm on it!! –  Michiel Apr 2 '12 at 9:43

Upgrade install (from Leopard)

Since you need the Mac App Store, Snow Leopard is required to install Lion. But when you have a copy of Lion (being a bootable disk mentioned above or a Thumb Drive), you don't need Snow Leopard to install Lion.

It's more of a brute-force method, but it will work.
There are three main steps in this process. Backup your data, clean your hard drive and install Lion on the clean drive.

There is a more in-depth tutorial on how to install Lion over Leopard.

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