Trying to setup my external with a couple partitions, one for encrypted Time Machine backups, and the other as ext4 for linux stuffs, yielded a no-go.

In short, Time Machine wouldn’t let me encrypt my backups which I dumped on the first partition of my disk. Turns out this is because I used the older MBR partition scheme.

These are the requirements in order for that check box to be clickable:

  1. You must be using a GPT partition scheme.
  2. You must be using the Mac OS Extended (Journaled) filesystem (HFS+).

If the Encrypt checkbox is available, you can select it to keep your backup disk secure. If the Encrypt checkbox is dimmed, your backup disk doesn’t support encryption.

Encryption is available only for Time Capsules and for partitions or disks attached directly to your computer and partitioned with the GPT partition scheme. If encryption is not available for your disk, put the mouse pointer on the dimmed checkbox, and after a moment an explanation appears. If a disk needs to be reformatted or repartitioned to support encryption, Time Machine prompts you to do so.

You can learn more about Time Machine from the official page. Enjoy:)

Mario Loria is a builder of diverse infrastructure with modern workloads on both bare-metal and cloud platforms. He's traversed roles in system administration, network engineering, and DevOps. You can learn more about him here.