hoakley September 19, 2021 Macs, Technology

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.

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1

bwillius on September 19, 2021 at 11:49 am

macOS is becoming more like Windows with every year.

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- 2
  
  hoakley on September 19, 2021 at 9:21 pm
  
  Thank you.
  That’s a fascinating comment. As I haven’t used Windows for some years, it doesn’t accord with what I recall, so perhaps Windows has changed greatly since then?
  One particular and general advantage of the new sealed system is that its integrity is protected and guaranteed, by the fact that it’s a snapshot and has its Merkle tree of hashes culminating in the Seal.
  It’s not long ago that macOS was criticised as becoming more like Windows because it had to be reinstalled so frequently. The sealed system volume surely means that it’s almost never reinstalled now, which I would have thought made it much less like Windows. Unless Windows has now adopted a similar system of protecting and guaranteeing its system integrity. Have I missed that?
  Howard.
  
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3

Sebby on September 19, 2021 at 12:56 pm

Uptime of my 10.14.6 iMac: 65 days and 15 hours. The Linux VM atop it is clocking nearly half that, at 30 days. Do you suppose I’ll see anything like the peace and tranquility I am now in my future? I doubt it.

In principle I do not object to an atomic system, but only if I gain a benefit, not unlike how ChromeOS updates happen essentially transparently. Maybe that will happen in future. Maybe it will make the monstrous bloating of the updates worth it. But surely, if iOS is any guide, the updates could get smaller. Even if we lose the ability to minimise the overall amount of downloaded data (which is obviously very noticeable over a slower connection, but can be done in the background at least) it ought to be possible to make the update process as seamless as possible. But on the other hand, it seems clear that being able to maintain a portfolio of offline installers is something we are going to have to accept may not be in our futures, and this time it will be a constraint of the available bandwidth and bandwidth cap that prejudices those choosing to maintain full installers over allowing any system to update in place, notwithstanding the benefit of the content caching server you may have on your network. This move seems to me to be utterly inevitable and, anyway, with the new activation requirements, it’s actually quite hard to argue that one meaningfully has sovereignty over one’s own hardware anyway.

And what about other operating systems? Windows, when not feature-updating (a dead end for all Intel Mac owners, of course, because they don’t have TPM 2.0) typically is under a gigabyte–quite often, no more than a few hundred megabytes. Linux? Package managers rule, and indeed tools like apt-cache and jigdo mean that you can construct entire boot medias using pre-downloaded package files, so that you can genuinely maintain both valid systems and valid media with limited bandwidth use.

I wonder if having a very fast connection would change my impulse to store offline media. Probably not, in fact it may make it preferable and easy. At the very least, it would reduce any anxiety about updating in place, as I could do it essentially at a time of my choosing and using the supported path. No doubt, in Silly Valley, that’s the thinking. And why not? Instead of planning for an automatic update that can happen at the wrong moment, just spend a few minutes on the download and initiate it immediately. Given that one can get any version of the OS at any time for several releases, it’s probably not even necessary to maintain old versions at all either; that’s just something the bandwidth-conscious do.

Whatever happens, I hope things actually improve. Just my twopenneth.

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- 4
  
  hoakley on September 19, 2021 at 9:26 pm
  
  Thank you.
  Don’t stop keeping old installers: Apple only provides a recent selection, and regularly drops older ones. For example, macOS 11.3 is no longer available any more. If you need a copy, then the only way to ensure that is to have saved a copy when it was still available.
  Howard.
  
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5

ShadowfactsDev on September 19, 2021 at 11:23 pm

Is it known that the massive update size is because of the SSV? I was under the impression that it was (at least partially) driven by the requirement of shipping an entire new dyld shared cache every update?

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- 6
  
  hoakley on September 20, 2021 at 5:23 pm
  
  Thank you.
  The dyld cache is widely touted as the main cause, but I’ve looked for evidence, and it isn’t consistent. For example, 11.5.1 contain just security fixes which changed nothing in the Frameworks at all, yet its size was just the same as the minimum. In any case, the whole of those caches don’t need to be replaced every time there’s an update. I’m sure that Apple’s engineers are more than capable of being more economical in updating the caches. Also, if you look at their sizes, even with remarkable compression, there’s no way they’re going to reduce to 2.1 GB are they? They also don’t explain why M1 Macs need 950 MB or so more than Intel models, although both architectures get the same updates, as everything is Universal.
  I also think the SSV is one reason that Apple is using those dyld caches. Could you imagine hashing every file in those Framework folders?
  Howard.
  
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7

Annapurna on September 20, 2021 at 1:41 pm

or use the app
https://twocanoes.com/products/mac/mac-deploy-stick/
that compiled all versions

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- 8
  
  hoakley on September 20, 2021 at 5:24 pm
  
  Thank you. Yes, that’s a boon for the sysadmin, but it still relies on Apple’s installers for macOS, it’s just a very efficient way to deploy them.
  Howard.
  
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9

Michael Tsai - Blog - macOS 11.6 on October 19, 2021 at 11:45 pm

[…] Update (2021-10-19): Howard Oakley: […]

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