SuperDuper! app icon among Mac hard drives and keyboard
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The developer of SuperDuper! say that what they believe to be a bug in macOS Sequoia 15.2 has inadvertently broken how the app can create bootable backups — however, it may not be a fluke at all.
It's been a few years since Apple took steps to at least make it harder for people to boot up their Macs using external drives. It's been a privacy issue, a security issue, and a minor headache for anyone who remembers Mac drive failures.
Now, according to developer Dave Nanyan, Apple has gone further, perhaps unintentionally. Nanyan is the developer of the backup app SuperDuper!, and says that since macOS Sequoia 15.2 changed a feature called Replicator, his app has been unable to create bootable backups.
“macOS 15.2 was released a few days ago with a surprise. A terrible, terrible surprise,” he wrote in a blog post. “Apple broke Replicator. Near the end of replicating the Data volume, apparently when it's about to copy Preboot or Recovery, it exits with a Resource Busy error.”
That means that at the last moment, a backup that was supposed to create a bootable copy of the user's macOS system will fail.
“Because Apple took away the ability for third parties (like us) to copy the OS and took responsibility for it, they had to make sure that functionality continued to work,” Nanyan continues. “And that’s where they failed in macOS 15.2.”
“Since it’s their code and we have to rely on it to copy the OS, copying the OS won’t work until they fix this,” he says.
The reported bug relates specifically to creating a backup from which the user can then start up their Mac. It does not affect backing up data to external drives.
Consequently, Time Machine is reported to be working properly for now. There have been no reports of the issue affecting other backup apps yet.
This may be because other backup apps have moved away from offering full bootable backups. Carbon Copy Cloner, for example, says it can only make a “best effort” to create a bootable backup for certain use cases, such as migrating between Intel Macs.
Otherwise, the company explicitly states that it does not support creating a bootable disk as part of a regular backup strategy.
As recently as 2021, Carbon Copy Cloner made bootable backups, but its founder said those days were limited due to the direction Apple was taking macOS. Apple Silicon uses a signed system volume, and if it gets corrupted, the Mac will reportedly not boot — possibly even if the user had an external boot drive.
“We can’t fix it… Apple needs to do it,” Nanyan says. “It’s a shame it’s happening during this time, as Apple rarely releases updates between now and the New Year.”
Nanyan may be right that this macOS Sequoia 15.2 issue is a bug. But it's at least as likely that this is a deliberate final nail in the coffin of third-party developers who can't create bootable discs.
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