Always keep a Backup.

My advice to people on here is as follows, once you have installed a bootable Mac OS on your hardware then buy/use a spare HD and install it again, it doesn't matter if everything works just so long as it's bootable, once you have done this keep the HD safe and stashed away somewhere. If your main MacOS is rendered unbootable and you have no access to another MacOS to make installers/ un-install system extensions etc then it's a nightmare trying to get it going again (I actually resorted to buying a white MacBook running mountain Lion just incase with a saved system image from my main computer)

submitted by /u/CheeseletIam
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