The install of El Capitan, at least what I thought was the installation, took a while. A screen shows up with the 10.11 logo stating to install click continue, agree to terms and install OS, I got the option to use disk utility, time machine or recovery or click the install button. I want to reset my iMac (late 2014, 1 TB Fusion Drive) to factory settings. As I want to set it back to Yosemite, I am using Internet Recovery (Command-Option-R) as I have installed El Capitan in the meantime. I was able to erase the HDD just fine in Recovery Mode Disk Utility, but now I am stuck. The OS X install dialog shows no available drive.
“This copy of the Install OS X Mavericks application can’t be verified. It may have been corrupted or tampered with during downloading”
I'm unable to complete the installation of El Capitan. I only have the HD & RAM memory installed (no battery). Other Mac OS-X Versions are installing OK (even Windows). But, when I try to upgrade to El Capitan it never finishes the update. Also, it will not install via USB thumb drive. I have tried everything! Once you’ve done that, here’s how to install, reinstall, or upgrade to El Capitan, step by step: Boot from your Recovery HD partition by restarting your Mac while holding down the Command+R keys. The OS X Utilities window appears. Select Reinstall OS X, and click Continue. The OS X El Capitan splash screen appears.
The reason why this insane message is happening is because as of February 2016, the security certificates that validate these Mac OS X installs seems to have expired. What this means is that when you try to install Mac OS X Mavericks, Yosemite or El Capitan from any USB or external source, the certificate checking process will render your copy of the installer null and void. You will then get the error “This copy of the Install OS X Mavericks application can’t be verified. It may have been corrupted or tampered with during downloading.”
Thankfully, as annoying as this is, there’s a pretty easy fix in the Terminal, located on every installer of Mac OS X. Here’s what to do:
- Boot into the OS X installer as you would normally do (hold down option at boot and choose your installer
- Disconnect the ethernet cable if it’s connected and turn off wi-fi from the networking menu
- Open the utilities menu item and choose “Terminal”
- When the Terminal appears, simply type in the following command: date 0202020216
- Hit return and you will now see the new date as read back by the system
- Quit the Terminal
- You can now begin to reinstall OS X from the main screen as you did before
Why does this work in the Mac OS X Terminal?
Why Can't I Reinstall Os X El Capitan
The reason why this works is that you are actually turning your computer into a time machine–and you are telling it to go back to the date February 2nd, 2016. This tricks the certificate into believing that the date is now in the past and allows the installation to resume. You can also redownload any installers to get the new certificates, which are located in your purchase history on the Mac App Store. You would then have to make new installer disks with these new downloaded installers.