How to Turn Your Mac Into a Local iCloud Server

What is content caching?

Used to speed up the downloading and installation of software on Apple devices, content caching is a service that helps reduce internet data usage. By enabling this service the Mac will save software updates, apps and other content as well as iCloud data such as photos and documents into a content cache that can then be accessed by other Apple devices. This will also allow the computer to share its internet connection and with any connected iOS devices connected by using USB.

The content caching service supports the following content, but is not a strict limit:

• iOS app purchases and app updates.
• iBooks Store content.
• macOS updates.
• Software distributed by Apple.
• Third party apps available in the App Store and their updates.
• iCloud photos and documents.
• On-demand resource support for iOS 10 and later, and tvOS 10 and later.
• iTunes U course materials.
• Uploaded instructor materials such as audio, video, iWork, and iBook Author files.
• Certain mobile phone assets, such as high-quality Siri voices.
• Language dictionaries.

This content is stored in a content cache on the computer and is available to all other devices connected to the same system without the need for an internet connection.

How does content caching work?

When you enable content caching, the ‘parent’ Mac will keep a copy of all relevant content on any locally networked devices (or ‘clients’). So if the first client is a Mac computer and downloads a macOS update, the content cache service will keep a copy of that update. This means that when the next Mac client connects to the parent, the update is automatically downloaded from the cache and not from the App Store, which doesn’t require an internet connection. This also means that the second client will receive the update much faster, given the nature of local connections and how they are much faster than the internet.

How to enable content caching

With macOS High Sierra, Apple moved the caching feature off the macOS Server, so now administrators can skip the step of running the Server app on caching servers. Here is how to set it up:

1. Launch the System Preferences and click on the Sharing pane.
2. Unlock the pane by clicking on the lower-left lock, and type in the admin password.
3. Enable it by clicking on the checkbox on the left side.
4. Configure the content caching service by holding the down the Option key while pressing the Options button.

To disable content caching, just simply uncheck the checkbox mentioned above.

Storage

Since the content caching feature downloads vast amounts of software, it requires an equally large amount of disk space to store all that data. The service options will allow users to set limits ranging between 2GB and 195GB or even allow unlimited space usage by using the slider in the options pane. This menu will also display how much space is used by the service. By the way, remember that this storage is purgeable, which means that if the Mac is running out of disk space, it will automatically clean it up.

It’s recommended to set a limit on content caching unless you have practically unlimited storage space available, especially if you have multiple ‘clients’ that will be connected together on the system. Cached files are stored on the boot volume by default, but another location can be chosen.

The Advanced Options configuration will give knowledgeable users more setup options, such as defining which devices can be defined as ‘clients’ and are therefore permitted to store data on the parent Mac. By default this is set to devices that share the same local network using one public IP address.

Content caching has huge advantages when dealing with multiple Macs and iOS devices, but there are just a few things to keep in mind before you start sharing content with clients:

• Install iOS 10.3 or later on all iOS devices.
• The parent Mac should connect to the internet via the Ethernet port.
• Plug the Mac into a power outlet, as the tethered caching service will prevent the machine from going to sleep.

So what are you waiting for? Save time and local Wi-Fi bandwidth using a cart or a USB hub, and update several devices at once using content caching.