Last Week on My Mac: the macOS update problem

We’re now on the cusp of change. Over the next few weeks, some of us will upgrade to Monterey and start its new cycle of updates, hoping that their total size will be significantly less than those released for Big Sur. Others, including many whose Macs aren’t compatible with macOS 12, will start the next year of security updates, wondering how onerous they’ll be.

No matter how fast your Internet connection, updates are another part of the user experience, and an important part too. We all value the improvements they bring, and the vulnerabilities which they address, but those still come at a cost to each user. Every update loses us time when we’d rather be using our Macs rather than merely maintaining them. macOS updates have also brought a real risk of disaster: in the past, it’s been worryingly common for some users to lose access to their Macs for a day or two, sometimes longer, when an update goes badly wrong.

One great advantage of the new sealed system in Big Sur is that failed updates should be a thing of the past. Updating should now be almost totally reliable, and in the rare cases where something does go wrong, that Mac should be returned to its pre-update state or Recovery, ready to try again. It has been widely assumed that the primary purpose of Big Sur’s sealed system volume is for its improved security. Although that’s clearly important, improved reliability of updates and assurance of the total integrity of the system affect far more users directly.

So far the big disadvantage of the new update mechanism required to accomplish this has been the size of updates. Each has brought an overhead of around 2.1 GB on Intel Macs and 3 GB on M1 models. For users who upgrade to Monterey, those should be the worst case expectation over the coming year. But I think we have higher hopes, as Apple’s engineers can now devote their attention to improving update efficiency by driving that overhead down. I don’t see it falling below 1 GB, but provided that we keep reminding Apple politely that updates need to shrink in size, I hope that can be achieved over the coming year.

What worries me more just now is what happens to those who can’t or won’t upgrade to Monterey, and have the next year of security updates as their consolation prize. It has taken a lot of pressure for Apple to provide both a full updater and an IPSW image for macOS 11.6, which is surely the first security update of the coming year for Big Sur. It looks as if Apple intends to release no further full updaters or IPSW images, in which case those still wanting or needing to run Big Sur are going to have a very rough year indeed.

Those staying with Catalina can expect a similar series of security updates to last year’s, each of which is supplied as a minimal delta update through Software Update, or as a standalone installer package downloaded from a page on Apple’s Support website.

With Big Sur’s new updating system, Apple no longer provides any standalone installer packages. Those wanting to apply a security update to an existing macOS 11 system either do so using a delta downloaded and installed by Software Update, or they have to download the full installer app and run that locally.

If Apple doesn’t provide full installer apps for every single released version of Big Sur, including 11.6.1, 11.6.2, and so one through this first year of maintenance, Software Update will become the only means of bringing 11.6 up to date with all its security updates. It’s also unclear whether Software Update will be able to install the equivalent of a Combo update in a single download.

In a year’s time, when Big Sur has reached 11.6.5, for example, how will a user be able to install or reinstall that on their Mac? Will they have to download and run the 11.6 full installer app, then use Software Update to obtain and install a single Combo update to bring that up to 11.6.5, or will they have to plod painfully through each individual delta update starting from 11.6.1 and ending with that to 11.6.5? If they boot into Recovery Mode and from there choose to install Big Sur, will they be given 11.6 and have to update it to 11.6.5 through Software Update, or will they get 11.6.5 complete?

Apple needs for once to explain to users what it’s intending to do. If that doesn’t provide users with a convenient and efficient offline means of installing or reinstalling a fully patched version of Big Sur without the use of Software Update, then a lot of those users are going to be rightly angry.