Starting today, Apple has activated the ability to automatically download the image macOS Sierra on supported computers with the right to download the amount of free space on the disk. But even here there are some nuances.
Upgrading the system will not be loaded on computers with a lack of disk space, and even in the case of a successful download, which provoked the appearance of messages filled with storage, the system will automatically delete the update. If this did not happen, Apple provides an opportunity to remove the loaded macOS Sierra, as well as disable the automatic download – for this, go to System Preferences → the App Store , and deselect the Automatically download updates in the background.
macOS Sierra will be loaded automatically from next week, though some users report that has found a system image to disk, upload it to this day.