You can access the Terminal by clicking on the Utilities menu and selecting Terminal. Everything looked raring to go. Apparently my problem was that I had downloaded the installer a number of days ago and the certificates had expired. You download it through the App Store. The new Disk Utility is horrible. However, it would always get to 99% installation and then crash, sometimes with a final message - this installation is corrupt.
I found a proposed solution here: I tried it and it doesn't work. DiskMaker X is a free app that many find useful in creating a bootable install disk. Go through option one, then if you have a legit, official copy of the installer, check your disk, then just try to burn the installer again. This isn't about money or subversion. Your Mac should now have the current date and time. The date should be set.
The installer or the volume it's going to install onto. The date was correct and the file verified, but it still would not install. To fix the issue, I had to boot from an external drive I had lying around, and changed the time in the system preferences. If all else fails, let us know. It looked like things were moving along, until this appeared on the screen. If you're already doing as the message suggested and haven't finished the new download and tried installing again, then why did you even post to begin with? When you get to the El Capitan page in the App Store, click on the Download button. I misread the dates on this post and backdated to 2013 instead of 2015.
Your Mac should now have the current date and time. Go into the Terminal as described above, then follow these steps. None of those things has helped. Type the following command into Terminal, replacing with your Volume names. So that's one reason out. Here's what I went through.
Once the Terminal has launched, follow these steps. One is the obvious corrupted installer. If your date is correct, then proceed to the next section below. It may have been corrupted or tampered with during downloading. Please share your tips, tricks, hacks, creations, and humor related to the best desktop environment out there. The filesystem on disk and the sharing protocol are 2 different things, and the file system is abstracted via the share.
Click the padlock to unlock that pane. I simply could not get one. If you enter date again as I did in the screenshot above the information that appears will be current. You could even disconnect any network cable during the install. How can I fix this? How much space is used? You have to use the Terminal to set the date and time.
If it still fails with the same error message, proceed to next steps below. I think many people think setting the date to the current date automatically fixes the issue, but this is not the case. Issues on trying to do this are well documented so I wont dwell, other than to say my last App Store download was 10. If it's saying the volume you're installing onto cannot be verified, you can try erasing it again. Or you can use your Mac while you wait, but be ready to save your work and quit when the download is done.
For example, the 7th is 07. Apple may have changed its check routine and date stamp in 2017. Try re-downloading El Captain and re-copying it to your media. 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. I can boot from the thumb drive, but when I try to install Yosemite, get the error above. That will allow more apps to open for you without that window appearing many folks call that the Gatekeeper window Thanks everybody for your responses.