While I haven't tested the process myself, there is a blog post on The Eclectic Light Company titled How to back up your iCloud Keychain:
It suggests that you can force your computer to locally sync a copy of the iCloud Keychain into your standard keychain files by temporarily disabling iCloud Keychain, after which you will be able to back up the local keychains, and then re-enable iCloud Keychain sync:
The best way to ensure that you have a full local backup of all those passwords and other essentials in your keychains is to periodically come off iCloud Keychain to force-sync them into local storage, then enable iCloud Keychain again, and back your ~/Library/Keychains
folder up.
When you turn iCloud Keychain off, macOS should invite you to keep a copy of your passwords and credit cards on this Mac. Click on the Keep on This Mac button to do that. Your Mac will then ensure it’s fully synced with iCloud, and saved to your local storage. This includes ~/Library/Keychains/login.keychain-db
, which remains your main user keychain used from the moment that you log in, and at least one set of keychain-2
files stored in a folder whose name begins with a UUID, inside ~/Library/Keychains
.
When your Mac has iCloud Keychain disabled, all those password items in your iCloud keychain are held in the keychain named Local Items. Thats the active set of keychain-2
files stored in a sub-folder whose name begins with a UUID.
/Library/Keychains
does not contain aniCloud.keychain
file