How do I encrypt or password protect the external hard drive I use for backups

Hi JoeBar44,

If you haven't already erased your backup drive, you may be able to encrypt it while preserving your backups. While this process is the most secure option, it may take a long time to complete. Be sure to always properly eject your drive before physically disconnecting it to ensure that the encryption process isn't disrupted.

Unfortunately, Finder doesn't seem to offer an option to encrypt Time Machine backup drives in the Finder. However, you can accomplish this in Terminal:

1. Open Terminal, located in Applications -> Utilities.
2. Note the name of your backup drive.
3. Type this command and hit Enter. Replace driveName with the real name of your drive: diskutil apfs encrypt "driveName"
4. Follow the onscreen prompts in Terminal. If you're asked for a password or passphrase, type it and hit Enter. Terminal won't show any characters or indication as you enter the encryption password or passphrase.

JoeBar44 wrote:

Hi it is a Time Machine backup drive. I get messages stating although my Mac is encrypted my external drive isn’t.

That is normal. Turning on FileVault on your Mac doesn't automatically encrypt your external Time Machine backup drive.

See: Keep your Time Machine backup disk for Mac secure - Apple Support

Hi,

If it's not a TimeMachine backup drive, select it in Finder > right click or Control click on it > select Encrypt.

You can format to APFS encrypted and start a new TM drive if so desired.

tbirdvet wrote:

You can format to APFS encrypted and start a new TM drive if so desired.

Yes, but doing that would leave the previous data unsecured (unencrypted).

You need to start fresh with the backup.

Thanks for posting! Glad to help.

Quick correction to my previous command, if you choose to use it: diskutil apfs encrypt "driveName" -user disk