How to change FileVault password. This is useful when wanting to have two separate passwords; one for the disk and one for the login account.

• https://support.apple.com/en-us/HT202842
• https://apple.stackexchange.com/questions/125087/how-can-i-have-one-password-for-filevalue-2-pre-boot-password-and-another-for/125120#125120