To anyone trying to install the GM while running a OS X dev build: <a href="https:&#x2F;&#x2F;neosmart.net&#x2F;blog&#x2F;2015&#x2F;upgrade-to-os-x-el-capitan-gm-from-a-dev-seed&#x2F;" rel="nofollow">https:&#x2F;&#x2F;neosmart.net&#x2F;blog&#x2F;2015&#x2F;upgrade-to-os-x-el-capitan-gm...</a><p>You&#x27;ll need the whole 6 GiB download, there&#x27;s (currently) no delta upgrade available. It also doesn&#x27;t seem there will be, based off of the note from Apple (see link).