I have MacBook Air and I have installed Yosemite on it. Whenever I boot my Book, I get a 'Update Required' message and I end up updating my OS. I don't think that Apple releases an update each day, does it? What might be causing my Book to update Yosemite each time I boot? How to fix this or stop the update every time I boot?
How to fix Yosemite not to update all the time?
I think that happens because when you did update your Mac OS X you probably didn’t install all the updates or you forgot to install the remaining updates for Mac OS X Yosemite. To make sure all updates are installed, click on the Apple menu then select Software Update. Check for updates and install all the updates that will be appearing on your screen.
Aside from doing that, you can also check all the updates for your Mac PC from Apple Support Software Updates and Downloads. This page lists all the current available updates for different and recent Mac OS X operating systems. Mac OS X Yosemite has 2 available updates to download. Mac OS X Mountain Lion has one and Mac OS X Mavericks has one.
The remaining updates are for iOS devices, digital cameras, and printers. To install the updates, download the updates applicable to your operating system and then install them manually. Restart your computer when it is required.