Some issues on your Mac can be resolved by reinstalling the operating system. In the past, all Mac desktops and portables came with a dedicated recovery disc for that machine, but Macs shipping with 10.7 (OS X Lion) or later do not come with recovery discs.
These newer machines have the recovery files on a separate partition on the hard drive. Knowing these steps can come in handy if you ever need to reinstall the operating system to resolve a software problem or upgrade to a larger drive. It is also useful if you want to wipe your data and install a clean version of the Mac OS before selling or giving away your machine.
There are two types of installs. You can do a clean install, which will format the hard drive and erase all data, and then install a clean version of the OS. The other option is an OS reinstall which installs just the important OS files and leaves the user data intact.
Before doing either of these, it is important to back up all important data due to the possibility of failure during the installation process that can compromise your data.
These steps only apply to machines running 10.7 (OS X Lion) or 10.8 (OS X Mountain Lion), and require a high-speed internet connection. The actual OS files are located on Apple’s servers, and are downloaded every time you install.
Warning: Make sure all important data is backed up before proceeding.
1. While the machine is shut down, power the machine on and hold down the Option key. Then select Recovery HD.
2. After selecting the*Recovery HD* it will boot to the Mac OS Utilities window.
- If you want to Install the OS and keep the user data intact, select Reinstall Mac OS X.
- If you want to reinstall the OS and erase all data, select Disk Utility. Then select the hard drive in the left hand column. Select erase from the second tab, and then erase at the bottom right to confirm wipe. Then close Disk Utility and select Reinstall Mac OS X.
3. After the installation completes the machine will reboot.
Stay tuned for part two next week on how to create a bootable Lion or Mountain Lion USB flash drive.