Do this quickly, as it may automatically reboot for you after a 30 timeout period (although if you’ve got an unsaved document open, you should be able to prevent that).ġ0. This will be fine as long as you don’t let the app restart your machine. Once the installer finishes download and prompts you to restart your Mac, force-quit it. Once the file finishes downloading, the installer will extract the InstallESD.dmg image from it and delete the package. I just kept an eye on it and force closed it before the timer counted to 0.ĩ. This will give you a little insurance against the installer rebooting the system, since the app won’t let the system reboot until you respond to its message asking whether you want to save the document or not.

commands in the File menu (I used TextWrangler) and make a new unsaved document, and type a few things in it. Open an old-style (non-autosaving) application that still uses the traditional Save, Save As…, etc. When the download has finished the installer will re boot your Mac, so we need to stop it from doing this. For this i used a 16gb USB memory stick.Ĩ. Enter your admin password when prompted, and the installer will start downloading. Once it asks you for a disk to install on, choose the external drive or spare partition. Hdiutil attach “/Volumes/Recovery HD//BaseSystem.dmg”Ħ. Now, from the newly mounted Mac OS X Base System image, double-click the ‘Install Mac OS X Mountain Lion’ application at the root of the disk.ħ. Go through the license agreement.

The disk image inside the recovery HD is invisible, so use the Terminal to mount that too: Replace above with the identifier you obtained from step 2. Type the following command to mount the recovery HD:ĭiskutil mount readOnly /dev/Ĥ. It will be something of the form diskXsY, where X and Y are numeric digits, for me the identifier was disk0s3ģ. Look for ‘Recovery HD’ in the list, and note its identifier. Open the Terminal, and type this command to list all partitions on your hard drive or SSD:Ģ. Here is how i obtained my InstallESD.dmg From my Macbook Air:ġ. I found some old instructions on Macworld aimed at doing the same for OSX Lion on a Macbook Pro also worked for OSX Mountain Lion on my Macbook Air. It turns out you can extract a full OS X 10.8 Mountain Lion install disc from your Macbook Air / Pro quite easily. So i needed some way to obtain the InstallESD.dmg, this would allow me to burn it to disc (if my Air had a DVD drive) create an installable USB stick for OSX or simply create an ISO so i can burn the install DVD on Windows. However as OS X 0.8 Mountain Lion came installed on my Macbook Air i could not obtain the InstallESD.dmg from the App Store.

I own a Macbook Air and wanted to extract an OS X 10.8 Mountain Lion InstallESD.dmg from the Air.

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