Upgrading to El Capitan with an old installer

• 1 min read
guidemac-os-x
This post was published in 2016 and is kept here for reference. It may contain information that's outdated or inaccurate. All external links and references have been updated to point to archived versions on archive.org where possible.

I upgrade my Macbook to El Capitan as soon as I could, and have had very few issues with the release. On my iMac at work though, I’ve been putting off the upgrade since last October – due to time constraints and not wanting to mess anything in my dev environment up.

Today I tried to install El Capitan using the Install OS X El Capitan.app installer.

I was greeted with this message. How could this be? The installer has simply been sat in my Applications directory since October, nothing has changed.

I used the following command to verify the integrity of the installer image:

hdiutil verify /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/SharedSupport/InstallESD.dmg

Which told me the image is VALID. Alright, so there must be another cause?

Well I downloaded the installer in October 2015; In February 2016 Apple’s Signing Certificate expired. I actually encountered this issue when doing a fresh install of El Capitan on another Macbook earlier this year, the solution is simple: change the system date to earlier than February 2016.

date 1021120015

That command changes the date to October 21st 2015 at 12:00.

Alternatively you can use the Date & Time System Preferences pane:

Now you can run the installer without issue.

After OS X El Capitan has installed, it will set the date and time back to their correct values.

Now, rather than having to re-download a 7GB installer image, I just have to download a 2GB update!

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