what can you do?

A managed server, myserver1, has a boot.properties file in the security directory. It was started
with the startManageWeblogic.sh script(.cmd in windows) and his boot.properties file was used for
its startup credentials.
You just used the administration console to change all administrator passwords. To continue using
boot.properties, what can you do?

A.
This is not possible. A boot.properties file can be used only with the Administration Server.

B.
Delete boot.properties. In the administration console, under the myserver configuration, select
Generate Boot Identity file.

C.
You need not do anything- The password in boot .properties was automatically updated by
administration console when you changed the password.

D.
Edit boot.propetties. Type over the encrypted password with the new password in clear text.
The next time myserver1 is started, it will encrypt the password in the file.

E.
Delete boot .properties. Use the WLST encrypt () command to create a new boot.properties file
containing the new password. Copy that file into the security directory of myserver1

Explanation:
If you install the WebLogic Server Examples component, the default user weblogic
is created that has permission to start and stop WebLogic Server. The default password is
welcome1. If you change the password of the weblogic user, WebLogic Server does not
automatically update this password in the boot.properties file, which is located in the
DOMAIN_NAME/servers/AdminServer/security directory.
If you change the password for user weblogic, you can use either of the following workarounds so
that you can continue to boot a WebLogic Server instance via that username and its new
password:
* Remove the boot.properties file. Subsequently each time you start WebLogic Server, you are
prompted for the username and password. The changed password for the weblogic user will be
accepted.
* Modify the existing boot.properties file, changing the username and password as follows:
username=weblogic
password=welcome1
Subsequently during the server startup process, the boot.properties file is encrypted again.
Reference: Oracle Fusion Middleware Oracle WebLogic Server Administration Console Online

Help 11g Release 1, Limitation Regarding User weblogic
http://docs.oracle.com/cd/E15523_01/web.1111/e13708/overview.htm