Originally, the keychain password is the same as the login password for the account. The login password can be changed in any of three ways:
- By the user, in the Users & Groups preference pane. In this case, the keychain password is automatically changed to the new login password
- By the administrator (if different), also in the preference pane. The keychain password is not changed.
- By anyone who has physical access to the computer, in Recovery mode. The keychain is replaced by a new, empty one with the new password, and the old keychain is saved with the old password.
To change a keychain password, launch the Keychain Access application and select the keychain from the list on the left. If the list isn't showing, select
View ▹ Show Keychains
from the menu bar, or press the key combination command-K. Then select
Edit ▹ Change Password for Keychain...
You must know the old password in order to set a new one. Otherwise you'll have to reset the keychain.