5 steps before install OS X mountain lion
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5 Steps Before You Install OS X 10.8 Mountain Lion

5 steps before install OS X mountain lion

OS X 10.8 Mountain Lion, the latest Apple desktop operating system, has been released and available for online download on Apple App Store now. I have a few pre-installation tips for you before you rush to upgrade OS X. These steps will ensure you have a smooth and stable upgrade, as well as future disaster recovery.

Table of Contents

1. Check system requirements

First of all, make sure your Mac can run Mountain Lion. The latest OS does not have high requirements but if your Mac is 4 year or older, check Mountain Lion requirements before proceed.

Your Mac must be one of the following models:

  • iMac (Mid 2007 or newer)
  • MacBook (Late 2008 Aluminum, or Early 2009 or newer)
  • MacBook Pro (Mid/Late 2007 or newer)
  • MacBook Air (Late 2008 or newer)
  • Mac mini (Early 2009 or newer)
  • Mac Pro (Early 2008 or newer)
  • Xserve (Early 2009)

Don’t forget to check available disk space too! Mountain Lion installation needs at least 8GB of free disk space.

2. Repair disk

Mac OS X Recovery Utilities
Mac OS X Recovery Utilities

Save all your works, quit all programs and restart your Mac. Hold down Command + R to start Mac in Recovery Mode.

Run the Disk Utility to repair disk permissions and repair disks. This will ensure disk files and permissions have no error before upgrade.

I would recommend to run DiskWarrior to repair and rebuild the Disk Directory.

Restart Mac after complete the tasks.

3. Backup!


Backup your important files to flash disk, online storage, etc. Backup everything to Time Machine. If possible, create a full bootable backup (external disk) using SuperDuper! or Carbon Copy Cloner.

4. Download Mountain Lion (Don’t install!)

Do Not Install OS X immediately
Do Not Install OS X immediately

After all the preparations, now you may launch App Store to purchase and download OS X Mountain Lion (App Store link). The download size is over 4GB. It took me hours to download using a 4Mbps broadband line.

After download completed, the “Install OS X” will launch automatically asking you to continue setup.

WAIT! Do NOT click the “Continue” button yet!

5. Make a copy of InstallESD.dmg

Copy InstallESD dmg file
Copy InstallESD.dmg file

InstallESD.dmg is the actual OS X installer. It is needed to create an bootable recovery disk that can be used to install OS X on multiple Macs you own and reinstall OS X later. It will be a Godsend when you need it.

Because InstallESD.dmg will be automatically deleted after OS X installation, it is important to make a copy of the file before you continue with OS X installation.

  1. Open “Finder”, navigate to your Application folder. Find “Install OS X Mountain Lion”.
  2. Control+Click (or, Right-Click) on “Install “OS X Mountain Lion” icon, select “Show Package Content”.
  3. Goto “Contents” folder ➤ “ShareSupport” folder
  4. Copy InstallESD.dmg file (4GB+) to somewhere you can remember, such as Desktop.
  5. Done.

After you have the InstallESD.dmg file, you can self-create a bootable recovery disk or use Lion DiskMaker free tool to create one.

Finally, Install OS X Mountain Lion

OS X 10.8 Mountain Lion
OS X 10.8 Mountain Lion

Now, your disk is fixed. Your files are backup. You have a bootable recovery disk.

You are ready to upgrade Mac to OS X 10.8 Mountain Lion!

The installer will take a few minutes to copy files, then restart for installation. Then, it will restart again and boot into OS X Mountain Lion!

The whole installation process took me less than an hour. So far, everything is smooth for my old iMac (early 2008), except that few apps were incompatible with Mountain Lion (auto moved by installer).

Hope these preparation tips help you to have a smooth Mountain Lion installation. If you have any questions or want to add anything, please add your comment below.

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