I have two MacBook Airs, but I have very limited bandwidth. I would prefer to download updates once and then copy them onto all the other MacBook Airs. How can I download App Store updates once to update multiple Macs?
There are two types of update.
OS X software updates are updates for the OS and OS components (e.g. iTunes). These used to be delivered through a separate software update app, but since the introduction of the Mac App Store, the OS X updates have been combined with Mac App Store updates in the Updates tab of the Mac App Store. However, the CLI tool remains, giving you more flexibility in Terminal and allow the downloading of updates without installing them, perfect for copying to other machines before the installation takes place.
You can download OS X updates without installing them (which would automatically remove them) so you can copy them, using the following command:
The 10.9.4 update is distributed externally, outside of the Mac App Store; the Mac App Store just provides the UI for the installation process.
Conversely, for Mac App Store apps, you need OS X Server's Caching service, as the apps are 'non-transferrable' and the app receipt must match the Apple ID that downloaded the app for the app to be updated in the future. However, if you're using the same Apple ID, or don't care about updating the app from the second machine, update the app normally then copy the .app bundle from /Applications to the other Macs as necessary.
For third party stuff, you're pretty much restricted to downloading through the store, but many of those updates can be accomplished on secondary Macs simply by copying the App file from one Mac to the others. This does not always work, but usually will for the simpler Apps.