With the public beta out for macOS 10.15 Catalina, you might be a thrill seeker and want to test out the in-progress version. But maybe you’d like to hedge your bets. In the past, you’d need to partition your startup drive, which could turn into a lot of effort, or get an external drive—preferably SSD—and install and boot from that.
However, there’s a better way to have your Catalina and boot it, too. It’s even a path Apple documents and recommends.
With Apple’s not-quite-so-new APFS filesystem that replaces the long-running HFS+, drives are no longer organized into partitions, but volumes and containers. A container gets a pool of a fixed amount of storage on a drive when it’s configured, but containers can have multiple volumes. Volumes share all available free space within the container without requiring any other rejiggering—they grow and shrink automatically.
