But what if you like to format your Mac’s hard drive and start with a fresh install, or if you have multiple Macs to upgrade and just don’t want to download the big install file for every single one of them?
It’s easier that you might think.
Download the OS X Mavericks installer file
The solution is to get the install file locally to one of your mac’s and then prepare a USB drive that can be used to boot of and install Mavericks onto any Mac. The easiest way, and now for free is to download the installer from the app store. If you only see the option to install rather than download, simply start the install procedure and once the download is complete, rather than proceed with installing, go to the Applications folder in Finder and save the file for future use (don’t delete the original), preferably to an external drive, especially if you plan on formatting your Mac’s hard drive.
Prepare the USB drive to boot and install Mavericks
The next tasks are done using Terminal, the command line tool of choice in OS X. You can find it in /Applications/Utilities or simply launch it Spotlight (cmd + space) and type Terminal. First, let’s find the path of your USB media that you want to use for the installs. Make sure your USB drive is plugged in and mounted. In Terminal, navigate to volumes and list your devices:
cd /Volumes ls
You should have at least two devices listed, one is your Mac’s hard drive and the other should be the USB drive. Note the name listed from the output in Terminal. With the name at hand, let’s get the USB drive prepared. WARNING: all data on the USB drive will be erased. Make a backup before proceeding.
Back in Terminal, issue the following command, replacing the word nameOfYourUsbDrive with the actual name, and be prepared to enter your Mac’s administrator password:
sudo /Applications/Install\ OS\ X\ Mavericks.app/Contents/Resources/createinstallmedia --volume /Volumes/nameOfYourUsbDrive --applicationpath /Applications/Install\ OS\ X\ Mavericks.app --nointeraction
Once you hit return and the process has started, you should see a similar confirmation dialog:
Erasing Disk: 0%... 10%... 20%... 30%...100%... Copying installer files to disk... Copy complete. Making disk bootable... Copying boot files... Copy complete. Done.
Back in Finder, the USB drive should now be labeled Install OS X Mavericks. If you see this, you’re golden.
Boot and install Mavericks from the USB drive
While booting a Mac with the USB drive plugged in, hold down the option key to bring up the startup disk menu. Select the USB drive to boot from to start the installation. Depending on the speed of your system, installation should take anywhere from 30 to 45 minutes.