Open Activity Monitor when your Mac isn’t doing a great deal and you’ll see hundreds of processes listed there. Even in a virtual machine with a minimum of services there are at least 500, and in a vanilla setup with no apps open a real Mac can exceed 700. Clearly some of those like WindowServer are essential, but aren’t there plenty we could do without? That’s a question I’m asked repeatedly, which this article tries to answer.
One of the first problems when trying to identify which processes we could do without is knowing what each does, and how they’re interrelated. I doubt whether any individual in Apple knows them all, and trying to establish what some do would be a challenge. If we assume that we need to identify just 500 candidates, and each takes an average of one week to research, that would take over 10 person-years, by which time they would all have changed again. Studying 500 targets that are ever-changing simply isn’t practical.
When problems get difficult, it’s often best to cheat, so I’m going to go for the low-hanging fruit and consider a well-known group of processes, those making Time Machine backups. I’ve been following these since macOS Sierra, and frequently study them in the log. They’re also good candidates for removal, as many folk don’t back up using Time Machine but use one of its alternatives. So some already have good reason to want to be rid of backupd and its relatives. They’re also relatively discrete: although they depend on other processes to function, I don’t know of any other subsystems that require Time Machine, making it potentially disposable.
Set up a basic VM in maOS 26.2 and, even though Time Machine has never been enabled, you’ll see its processes listed in Activity Monitor.
Here are backupd and backupd-helper showing they still take a little % CPU even when Time Machine is completely disabled.
They also take a little memory, here a total of 5.1 MB. While that isn’t much, added up over 500 processes it becomes worth caring about.
Those two processes are controlled by LaunchDaemons stored in /System/Library/LaunchDaemons, in property lists named com.apple.backupd-helper.plist and com.apple.backupd.plist. Here’s our first problem, as those are located in the Signed System Volume (SSV), so we can’t change them in any way. The same applies to the other 417 LaunchDaemons and 460 LaunchAgents that account for most of the processes listed by Activity Monitor. In the days before the SSV it was possible to edit their property lists to prevent them from being launched, but that isn’t possible any more when running modern macOS.
If we can’t stop the backupd-auto process from being run, is there any other way we could block it? To answer that we need to understand how it’s scheduled and dispatched.
Until macOS Sierra, Time Machine backups were run from launchd as timed events, but since then their scheduling and dispatch has been performed jointly by Duet Activity Scheduler (DAS) and Centralised Task Scheduling (CTS), using lightweight inter-process communication (XPC). DAS manages a huge list of activities including com.apple.backupd-auto, and decides when to dispatch it to CTS to run. For example, it won’t do that for the first five minutes after a Mac starts up, to allow other processes to run first.
Once that time is up, DAS decides to run the backup:
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