Apple's latest macOS Sequoia 15.3 update appears to have resolved a bug that prevented popular backup utility SuperDuper from creating bootable backups, according to developer Dave Nanian.
The fix addresses an issue introduced in macOS 15.2 that caused SuperDuper to fail during the final stages of creating bootable backups due to a "Resource Busy" error when attempting to copy system preboot or recovery files.
Apple requires third-party apps to use Apple's own replication tools rather than directly copying the operating system. When these tools malfunctioned in macOS 15.2, it directly impacted SuperDuper's ability to create bootable backups.
"macOS 15.3 is now out, and with it, a fix for the broken replicator," Nanian wrote on his Shirt Pocket Watch blog. "As such, macOS copying will work again with 'Erase, then copy' backups."
However, Nanian cautions that while the specific replicator bug has been fixed, this doesn't guarantee that booting from backup copies will work in all situations. This is largely due to changes that Apple has made in macOS and recent Mac hardware in the name of enhanced security.
For example, Apple Silicon Macs require that the internal SSD remains functional for external booting to work, meaning a Mac with a failed internal drive won't boot from a SuperDuper backup, even if the backup itself is perfectly intact.
