software download
OS X El Capitan Installer
Official OS X El Capitan Installer from the Mac App Store.
Un-archive the zip archive and you will get the app Installer. A bootable ISO or bootable USB can be made from this installer. Instructions on how to do that are on the Internet/Youtube.
Some links:
https://www.macworld.com/article/2981585/how-to-make-a-bootable-os-x-10-11-el-capitan-installer-drive.html
http://anadoxin.org/blog/creating-a-bootable-el-capitan-iso-image.html
NOTE: If you get a damaged message when launching, no need to worry. Run this command in Terminal:
xattr -c "wherever your installer is, drag and drop into terminal, and remove quotes."
NOTE: While installing, if you get an error message such as Apple can't
verify your computer, change the date setting November 1st, 2015 in
Terminal or System Preferences. It should work after that.
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