Create OS X Boot Disk

sudo "/Applications/Install OS X El Capitan.app/Contents/Resources/createinstallmedia" --volume "/Volumes/Untitled" --applicationpath "/Applications/Install OS X El Capitan.app"

sudo hdiutil attach "/Applications/Install OS X El Capitan.app/Contents/SharedSupport/InstallESD.dmg"
sudo asr restore -source "/Volumes/OS X Install ESD/BaseSystem.dmg" -target "/Volumes/Untitled" -erase -format HFS+
sudo rm "/Volumes/OS X Base System/System/Installation/Packages"
sudo cp -a "/Volumes/OS X Install ESD/Packages" "/Volumes/OS X Base System/System/Installation/Packages"
sudo cp -a "/Volumes/OS X Install ESD/BaseSystem.chunklist" "/Volumes/OS X Base System"
sudo cp -a "/Volumes/OS X Install ESD/BaseSystem.chunklist" "/Volumes/OS X Base System"
sudo cp -a "/Volumes/OS X Install ESD/BaseSystem.dmg" "/Volumes/OS X Base System"
hdiutil detach "/Volumes/OS X Install ESD"

• http://www.file-extensions.org/article/create-os-x-el-capitan-usb-bootable-drive