Archive for November 13, 2017

Monday, November 13, 2017

Local Time Machine Uses APFS Snapshots

Lex Friedman, writing in 2012:

With Lion, Apple introduced local Time Machine snapshots. This mostly-silent feature lets your Mac use free space on your main drive to create iterative backups of your files when you’re away from your external Time Machine disk.

By default, Apple disables local snapshots on desktop Macs; the assumption is that you only need them when you’re using a laptop, and that your trusty desktop machine is always connected to a Time Machine drive.

This was called Mobile Time Machine and managed by the mtmd process.

Apple, describing macOS 10.13 (via Accidental Tech Podcast):

Your Time Machine backup disk might not always be available, so Time Machine also stores some of its backups to your built-in startup drive and other local drives. These backups are called local snapshots.


  • A bright red tick mark is a backup that can be restored now, either from a local snapshot or your backup drive. When your backup drive isn’t available, only the local snapshots are bright red.

  • A dimmed red tick mark is a backup that can be restored from your backup drive after that drive becomes available. Until then, the stack of windows on the screen shows a blank window for that backup.


Time Machine in macOS High Sierra stores snapshots on every APFS-formatted, all-flash storage device in your Mac or directly connected to your Mac.

Howard Oakley:

Inevitably, depending on how full your disk is and how often new data has to be written to it, old versions of files will be lost over time, as they have to be re-used to make free space. But if you can keep a reasonable amount of space free on your internal disk, mobile Time Machine should give you a valuable means of going back to any version of a document over the last several days, maybe even weeks.

What in Sierra is of relatively limited value will, therefore, become very useful indeed in High Sierra – and come with no performance or storage penalties. For laptop users, this will be an important feature to consider when deciding how quickly to upgrade to High Sierra.

Previously: SuperDuper and APFS, Finder 10.9 Disk Space Embellishment.

Update (2017-11-27): Rich Trouton:

As part of macOS High Sierra, Apple has added a new feature to Apple software updates which require a restart. When these updates are installed onto a boot drive which is using Apple File System (APFS), an APFS snapshot is automatically created on the boot drive prior to installing the software update. An APFS snapshot is a read-only copy of the state that the boot drive was in at a certain point in time, so it can be used as a backup in case something goes wrong with the update.

App Nap, Automatic Termination, and Zombie Apps

Howard Oakley:

More recently, Apple’s apps have started to behave differently. Support tools like TextEdit and Preview enter this [zombie state] instead of quitting automatically, when they go into App Nap without an open document. You can observe this by starting them up and leaving then to go into the background without any open documents.

With a longer list of apps open and in the background, most of them now go into App Nap, as shown in Activity Monitor.

Bring up the Force Quit dialog using Command-Option-Escape, and you’ll see that they are still listed there as running.

Look at their icons in the Dock, though, and the normal black dot has vanished, as if the app has actually quit.

They’re also missing from the list of open apps in the App Switcher (Command-Tab).


macOS has therefore gone from having two basic states for apps, to four[…]

Howard Oakley:

To prevent all apps from becoming zombies, simply type the following into Terminal:

defaults write -g NSDisableAutomaticTermination -bool TRUE

When you next open an app like Preview, if you leave it unattended in the background with no open windows, it will just sit there, and won’t quit or become a zombie.

Howard Oakley:

This zombie state is possibly the most complete antithesis of all good human design. The app is still there, but the user can’t directly use or quit it. The only two ways of regaining control over it are to open a document which by default will be opened by that app, or to act as if opening the app again. As zombies are removed from the Dock, App Switcher, etc., the latter is often very inconvenient.


This sort of behaviour is probably most tolerable when it occurs in such one-shot viewer utilities. But when it becomes standard in major productivity apps like Pages, Numbers, and Xcode, you have to ask why macOS is being so deliberately deceptive of the user. As Apple glosses over the matter in a couple of terse lines, and then only in its developer documentation, we’ll never know its design intent.

Update (2017-11-15): Howard Oakley:

In the absence of anything better, I suggest that they are termed undead apps, which has no other meaning in this context, and should therefore be unambiguous. It also seems a good description as to what they are. And despite my previous assertion, it appears that they can only exist for any length of time in App Nap. Indeed, as I show here, all apps running under macOS Sierra and High Sierra are eligible for App Nap, irrespective of custom settings in their Info.plist file.

App Store Changes

John Voorhees, quoting Apple:

Soon, you’ll be able to offer new customers a discounted introductory price for your auto-renewable subscriptions on the App Store. iOS 11.2 introduces new classes … and new properties … to provide details on the introductory pricing and billing period you’ve selected for your auto-renewable subscriptions.

One step closer to trials.

Juli Clover:

As part of its newly updated App Store in iOS 11, Apple is introducing a new “This Weekend Only” feature for the “Today” section, which will see the company offering “new ways to save” with apps.

Apple will introduce an app with a special deal each Thursday, with discounts available through Sunday.

Twitter Sidestepped Russian Account Warnings

Selina Wang:

In early 2015, a Twitter employee discovered a vast amount of Twitter accounts with IP addresses in Russia and Ukraine. The worker, Leslie Miley, said most of them were inactive or fake but were not deleted at the time. Miley, who was the company’s engineering manager of product safety and security at the time, said efforts to root out spam and manipulation on the platform were slowed down by the company’s growth team, which focused on increasing users and revenue.

“Anything we would do that would slow down signups, delete accounts, or remove accounts had to go through the growth team,” Miley said. “They were more concerned with growth numbers than fake and compromised accounts.”

Previously: Yahoo Says Hackers Stole Data on 500 Million Users in 2014.