We have an iMac that is barely still compatible with El Capitan. Right now it runs Mountain Lion okay, and actually it has a smaller partition on the hard drive for another clean installation of Mountain Lion that we don't really use.
I have an El Capitan boot USB drive and an El Capitan install app, and I was thinking about using one of those to upgrade the clean install partition to El Capitan to see how it performs, but I'm hesitant and want to make sure things wouldn't be messed up.
So first of all, does this sound like a good idea? Second, would it be better to boot into the USB drive and choose to install to the clean install partition or should I put the install app on the clean install's Application's folder and run it from there?
With OS X El Capitan, Apple has built on many of the changes that were brought on by Yosemite. And as with previous OS X versions dating back to OS X 10.7, El Capitan is only available for install via download from the App Store. So if you previously relied on DVD installs, you won’t be able to do so with this version. The mismatch is occasional which proves that El Capitan is not all that different from Yosemite.) An alternative to reading the whole book is to use it as a reference while doing the hands-on exercises in the much briefer 'Teach Yourself Visually OS X El Capitan.' Part One: The OS X Desktop 1. Folders, Windows & Finder Tabs 2. Organizing Your. Apr 01, 2016 “This copy of the Install OS X Mavericks application can’t be verified. It may have been corrupted or tampered with during downloading” 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. If you are getting this Error Trying to down grade your Mac from OS X El Capitan its a simple time nag in the web installer. There is a simple and easy fix. Many Hackintosh users running Mac OS X Lion have been unable to login to the Mac App Store, instead receiving the error, 'Your device or computer could not be verified. Contact support for assistance.' The verification issue appears to have affected the several legitimate Macs as well, though on less wide of a scale.
Copy Of El Capitan Cannot Be Verified
Also would doing this risk causing the Mountain Lion restore partition to be deleted? Are there risks of things being messed up, not being able to make Mountain Lion the default boot partition, or other weird things El Capitan would do to the main partition?
If you are trying to install a fresh copy of Mac OS X 10.11 El Captain after downloading it from the App Store and you are using a bootable USB drive, you may receive an error message right before the install kicks off.
This copy of the Install OS X El Captain application can’t be verified. It may have been corrupted or tampered with during downloading.
This error message indicates the MPKG mechanism for checking the application installer checksum (used for proving the install files are valid and from Apple) files failed. It basically means Mac OS X will not proceed installing a copy of El Captain because it can’t prove its authenticity – even if the installation is ok. You can still push forward and install Mac OS X El Captain. Follow the steps below.
Everyone Says: Check the System Time on Mac
Apparently, the system time on your Mac may be off causing the El Captain installer to think your system date is way off. This happens if your onboard motherboard battery is toasted. Check the date to ensure it’s right – follow these steps.
1. Cancel out to the installation (If you are still on your bootable image of El Captain). Go to Utilities -> Terminal.
El Capitan Cannot Be Verified Full
2. Type date. If your date is correct, then proceed to the next section below. If it’s not correct, continue with these steps.
3. Set the current date and time. In Terminal, type the following command in this format shown in example below date MONTH(02)-DATE(28)-TIME(01:51pm)-YEAR(15)
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Hit enter to apply the new date. It will display. Now, attempt to install El Captain. If it still fails with the same error message, proceed to next steps below.
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Force Install El Captain Terminal Command
If your confident the install you just downloaded from the App Store is valid, just use Terminal to force install it. You can do this while still booted from your USB Drive or media. Follow the steps below.
1. Type the following command into Terminal, replacing with your Volume names.
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2. The install should kick off and you’ll see in Terminal “installer: OS Install started”. Wait for it to complete then reboot.
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Cannot Be Verified El Capitan
If all else fails, let us know. You may actually have a corrupt copy of El Captain in the end – maybe you disconnected your USB Jump drive incorrectly causing the files to become corrupt. Try re-downloading El Captain and re-copying it to your media.
Use the comments form to let us know if you have issues or found another way to bypass this error.