A Mac’s Recovery HD is a good solution to reinstall OS X. If your Mac is a Mid 2011 or newer model and you are running OS X 10.7 Lion or 10.8 Mountain Lion you can boot into the recovery system by holding down the option key at boot.
The recovery system which will be booted is very lean and downloads a macOS Image from Apple’s servers, this works for Ethernet and even WiFi connections. The big problem is, Apple did not add an option to set a proxy server! So if you are behind a proxy you won’t be able to use the recovery feature. That’s why I searched for a solution and found an easy one even for guys not that familiar with IT.
- Press option at boot to start the recovery system.
- Click Utilities in the menu bar and open Terminal.
- In the Terminal window enter: networksetup -listallnetworkservices
- The available networking devices will be shown, choose the one you will use (Ethernet, WiFi or Display Ethernet) for the Internet connection.
- Next you have to set the proxy and the networking device to use (choose off when the proxy does not force authentication): -setwebproxy Wi-Fi address.of.proxy 80 off
- If you use an automatic configuration script for the proxy and Ethernet instead the command should look like this: networksetup -setautoproxyurl “Ethernet” http://address.to.proxyfile /proxy.pac
- If there are no errors you can close the Terminal and start the graphical installation process.
When you need additional information to networksetup you can enter man networksetup in the Terminal.
NOTE: This workflow is not working on newer OS X / macOS versions. If you know a way to get it to work on OS X 10.9+ please let me know.