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I have this mid 2011 iMac 21.5" Core i5 on which I would like to install Linux (Debian) as the only OS, so I'd like to throw away the entire macOS installation. The web is full of tutorials for doing this, so, I think, this will be an "easy" step.

My problem is: what if in future I want to go back on macOS (e.g for selling the computer)?

I wonder if "OS X Recovery" (CMD + R) will work after the full Linux installation because I'll no longer be able to download macOS from Mac App Store and I have no installation CD.

The best solution I think could be: keep the recovery partition and install Linux on the rest of the disk, but can this be done? How?

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  • I know nothing about macos(or apple in general) but don't they use keys for there software (like windows?)
    – Junaga
    Oct 31, 2016 at 16:24
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    Why not making it dual boot+the recovery partition?
    – Rui F Ribeiro
    Oct 31, 2016 at 16:24
  • Because I thought it would be easier erase all, install only Linux (as if it was a "normal" pc) and not waste any more space. Anyway, I don't like the idea of having an unused operating system on my computer.
    – MarcoLucidi
    Oct 31, 2016 at 16:55

3 Answers 3

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Might want to use backup software for your personal files first...

  1. Buy a flash drive, 8 GB or larger, for this purpose.
  2. Download macOS Sierra from the App Store.
  3. Plug in the flash drive and rename it to "SierraInstallation" for the purpose of matching the command below in step five.
  4. Open Terminal or iTerm2.
  5. Execute, all on one line: sudo "/Applications/Install macOS Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/SierraInstallation --applicationpath /Applications/Install macOS Sierra.app --nointeraction"
  6. When the command has been completed, eject the flash drive and keep it to reinstall later.
  7. Proceed to the Linux installation, no need to keep any partitions.

To install macOS later...

  1. Plug in the flash drive to the Mac.
  2. Reboot the Mac and hold the Option key.
  3. Choose "Install macOS Sierra" from the boot options.

You might also want to keep a ZIP file of /Applications/Install macOS Sierra.app/ on another storage device, backup drive or what have you, in case you lose the flash drive or some other problem.

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  • 1
    Basically this process will create a macOS bootable USB right? And step 5 can only be done from macOS?
    – MarcoLucidi
    Oct 31, 2016 at 17:15
  • In order to save money I could use a pen drive that I already have, with "dd" I could create an img of the bootable usb and save it on my backup hard drive and then restore it if in future I will need, could work?
    – MarcoLucidi
    Oct 31, 2016 at 17:32
  • All right, thank you very much, I think I'm going to make this bootable macOS usb in order to keep a kind of "installation CD".
    – MarcoLucidi
    Oct 31, 2016 at 17:51
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    @Wildcard Why not? As far as I know, dd performs a block-by-block copy so, it doesn't care about which OS formatted that drive. Am I wrong?
    – MarcoLucidi
    Nov 1, 2016 at 8:54
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    @MarcoLucidi, only if both drives are completely inactive while you make the copy. Don't try using dd to copy from the drive you've booted from. See here for more details.
    – Wildcard
    Nov 1, 2016 at 18:28
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I was trying to install Debian on a mac mini this weekend (and failed because of lack of wifi firmware), but was able to successfully restore back to macOS.

Even though the Debian installer had partitioned the entire drive, when I restarted and held down the Option key, the recovery partition was still available, and I was able to boot to it and restore from a Time Machine backup I had previously made.

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  • This would be great. May I ask you if you had issues with the boot of the installer and later the actual OS? Did you use rEFInd or something like that?
    – MarcoLucidi
    Oct 31, 2016 at 18:08
  • Had no issues with the Debian installer (booted from USB after holding down Opt key), and install worked fine except that I had no internet connection when done, but Debian was running. Apparently I need some non-free firmware to make wifi work on the mac mini, and that wasn't on the installer I had. Will try again soon with another version of the debian installer that includes the needed firmware.
    – RaskaRuby
    Oct 31, 2016 at 20:50
  • Great to hear that! Well, if you have another pc, I think you could easily download the missing firmware and install it from a pen drive. Fortunately I will be able to connect the computer through an ethernet cable during the installation, hoping it will work "out of the box".
    – MarcoLucidi
    Nov 1, 2016 at 9:16
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From my viewpoint as a professional system administrator, the only proper solution is to make a full bootable backup clone of your entire hard drive before you install Linux.

As far as I know, there is only one piece of software available that will dependably make a bootable backup of a macOS computer. That is CarbonCopyCloner.

It's paid software (which I find well worth the price), but it has a full-featured time-limited trial. So for a one-time full backup, you won't need to pay anything.

CarbonCopyCloner also creates a recovery partition on your backup drive, if you ask it to. (And it will probably prompt you to do so even if you don't ask it to, but you can decline if you don't want a recovery partition. I don't know why you would decline.)

As long as you can still option-boot to choose a boot partition during startup after your Linux install, you should still be able to boot from the external drive, into macOS. Then you can use CarbonCopyCloner again (either within the trial period or by buying a copy) to restore macOS to your internal hard drive.

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  • Oh, the hubris. It hurts. This answer completely misses the point. Only "real answer." lol
    – Garland
    Nov 15, 2016 at 13:57
  • @Garland, it's not hubris. A backup of data is not a backup of your OS. A backup of your OS is not a backup of your data. That is a fact. What "point" is missed?
    – Wildcard
    Nov 15, 2016 at 19:06
  • Uh, "I'd like to throw away the entire macOS installation." Hello.
    – Garland
    Nov 15, 2016 at 21:48
  • @Garland, "what if in future I want to go back on macOS?" That's the exact purpose of backups—so you can effectively go back in time. Anyway, edited.
    – Wildcard
    Nov 15, 2016 at 21:53
  • Refer to comment #1.
    – Garland
    Nov 15, 2016 at 21:55

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