The Caching Server in OS X Server 5.2 (for Sierra) does content, apps, and
software updates. The Software Update service is hidden by default indicating it will likely be removed from the Server app in a future update, although when is kinda’ up in the air. The Software Update service can still be enabled for now, which we’ll look at later. The Caching service on the Server app works like a proxy. When 10 of your users download that latest Nicholas Sparks book and movie, you only sacrifice your WAN pipe to download it once, and the other 9 people piggy-back off that. And when 10.12.1 ships, you only need to download it over the WAN once, and the other local users will pull off that spiffy Caching server sitting in your office. Pretty sweet, right?
So, how do you use this ultra-complicated service? It looks and feels kinda’ like an iPad app. Which is to say that as far as server stuffs go, this thing is pretty darn easy to use. To get started, open the Server app and then click on the Caching service in the sidebar of the Server app.
Here, click on the ON button. OMG, so hard. But wait, there’s more! Click on that Change Location button and you can select a larger volume for your updates that are cached. You’ll likely wanna’ do this because the entire series of the HBO drama OZ is kinda’ big (and yes, creepy, but really well written)…
If you do change the location, you’ll see a window to change the volume you’re caching to. That’s pretty much it. Other than the waiting for the updates to move. By default, the Caching service allows for unlimited space. Use the spiffy slider to reduce the total amount of space that the service can occupy on the hard drive. This can be a good thing if it happens to be your boot volume and there are other more mission critical services hosted on that thing.
Overall, this all seems pretty straight forward. So what else might you need to know. In case you get a corrupt asset, or in case your volume fills up, there’s a Reset button, to reset the cache.
The service can be controlled from the command line as well. To start it, use the serveradmin command along with the start verb and the service name (oddly, that’s caching).
sudo /Applications/Server.app/Contents/ServerRoot/usr/sbin/serveradmin start caching
To stop the service, use the stop verb along with the service name:
sudo /Applications/Server.app/Contents/ServerRoot/usr/sbin/serveradmin stop caching
To see a list of settings, use the settings verb with the service name:
sudo /Applications/Server.app/Contents/ServerRoot/usr/sbin/serveradmin settings caching
The settings are as follows, mostly available in the Server app:
caching:ReservedVolumeSpace = 25000000000
caching:CacheLimit = 350000000000
caching:ServerRoot = "/Library/Server"
caching:ServerGUID = "DEE63BBB-9F32-428B-B717-E3941F82E2DC"
caching:DataPath = "/Library/Server/Caching/Data"
caching:LocalSubnetsOnly = yes
caching:Port = 0
One setting you might choose to change is the reserved volume space, as this can keep you from getting the service started on smaller volumes. In the above example, the setting is 250 gigs. To change that to 100 gigs:
sudo /Applications/Server.app/Contents/ServerRoot/usr/sbin/serveradmin settings caching:ReservedVolumeSpace = 10000000000
A new setting in Server 5.2 for macOS Sierra is defining other servers that can access your Caching server. This is like providing a proxy for a proxy. Basically if your devices can cache updates onto the server from other servers then the updates are caching much faster than if your server caches the updates from Apple. This is called Peering Permissions. To define Peering Permissions, click on the Edit Peering Permissions… button.
At the Caching screen, click on Only Local Subnets if you want to let the server identify which subnets are local, or Only Some Networks to define which ranges of addresses have servers that can cache content and update from your server.
Click on the plus sign to add a network and then click on “Create a new network”
At the Create A New Network screen, provide a name and then the first and last IP
Click Create and then add all of the appropriate subnets. Click OK when you’re done. Restart the service and viola, you’re finished.