OS X could not be installed on your computer.
No packages were eligible for install. Contact the software manufacturer for assistance.
Quit the installer to restart your computer and try again

Even if you did a clean install of El Capitan it would not explain why you are seeing OS X 10.6.8. OS X 10.6.3/4 was the original system on your computer. Still, it’s hard to know where the 10.6.8 came from, unless Time Machine has been disabled or disconnected for the last 8 years or so. My end goal was to install macOS 10.13 High Sierra. I read online that one must upgrade to OS X 10.11 before upgrading to macOS 10.13 if one is starting from OS X 10.6. This upgrade route did not work for me no matter how many solutions I attempted. As explained here, OS X 10.11 'El Capitan' fails to install because it is too old (the technical reason being that the signing certificate is no longer valid). But you can trick the OS X installer into thinking that it is 2017 and it will happily run without any errors. How to trick the OS X installer. The attempt to install data.table failed due to a problem compiling the package from source. Before trying to fix that, though, you might try installing the binary (already compiled) version that's available — it's not that much older than the source version. To try this, run: install.packages('data.table', type = 'binary').

Os X Could Not Be Installed No Packages Were Eligible For Install

Oh dear… When trying to install OS X 10.11 (El Capitan) you may encounter this message. This happens because the the installer certificates are no longer valid when checked against the clock of your mac.

Don’t panic though as this is easily fixed using Terminal, so don’t restart immediately.

How Do You Fix No Packages Were Eligible For Install

• Click Utilities on the menu bar
• Select Terminal
• Type date 062112422016
• Exit Terminal
• Click Restart

When you restart the mac and try the installer again it will now believe the certificates are valid and will continue as it should.

Os X Could Not Be Installed No Packages

• Install Homebrew

  
  

  Paste that in a macOS Terminal or Linux shell prompt.

  The script explains what it will do and then pauses before it does it. Read about other installation options.

• What Does Homebrew Do?

  
  

  Homebrew installs the stuff you need that Apple (or your Linux system) didn’t.

• Homebrew installs packages to their own directory and then symlinks their files into /usr/local.

• Homebrew won’t install files outside its prefix and you can place a Homebrew installation wherever you like.

• It’s all Git and Ruby underneath, so hack away with the knowledge that you can easily revert your modifications and merge upstream updates.

• Homebrew complements macOS (or your Linux system). Install your RubyGems with gem and their dependencies with brew.

• “To install, drag this icon…” no more. Homebrew Cask installs macOS apps, fonts and plugins and other non-open source software.

• Donate to Homebrew

• Homebrew Blog

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• Homebrew was created by Max Howell. Website by Rémi Prévost, Mike McQuaid and Danielle Lalonde.