I've just installed a new hard drive in my 2008 iMac. As my old one died I put a copy of macOS Sierra on a USB stick, but when I try to boot from it all I get is the no entry sign.

Any ideas what I’m doing wrong? Do I possibly need an older version macOS?

  • 2
    Glad this got fixed for you. I would appreciate an Accept of my answer when you've got a moment 😊
    – user11633
    Aug 13, 2017 at 14:55

2 Answers 2


You need at least a 2009 iMac to run macOS 10.12 Sierra.

The latest version of macOS that supports the 2008 iMac is macOS 10.11 El Capitan.

  • 3
    Cheers all working fine now 👌👌 Aug 13, 2017 at 14:49

True: For an officially supported version of a mac operating system you have to go with a maximum of El Capitan.

However, you may insist on installing macOS Sierra 10.12 on this unsupported machine.

That is made possible with overriding the Apple blacklist that prevents installation and results in the "No Entry Sign". This can be simplified with Sierra Patcher.

"Requirements: -Early-2008 or newer [… ] iMac, […]"

Known issue: There might then be issues with WiFi/Airport on iMac 8,2 models if they have an incompatible Airport card installed. Sierra lacks drivers for these. But the cards may be upgraded or an external adapter used.

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    This path is highly discouraged especially if this is a production (meaning you do daily work on it) machine. Per the website where this tool can be found: Note: Make sure SIP is disabled on the system you intend to install Sierra on. ... Please also note that SIP MUST remain disabled for as long as you run Sierra. Disabling SIP is disabling a core security feature of macOS.
    – Allan
    Aug 31, 2017 at 16:09

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