只需以下几步即可

oracle@DB-MASTER-1 ~]$ emctl setpasswd dbconsole 

Oracle Enterprise Manager 11g Database Control Release 11.2.0.1.0 

Copyright (c) 1996, 2009 Oracle Corporation.  All rights reserved.

https://DB-MASTER-1:1158/em/console/aboutApplication

Please enter new repository password: 

Repository password successfully updated.

[oracle@DB-MASTER-1 ~]$ emctl secure dbconsole -sysman_pwd oracle

Oracle Enterprise Manager 11g Database Control Release 11.2.0.1.0 

Copyright (c) 1996, 2009 Oracle Corporation.  All rights reserved.

https://DB-MASTER-1:1158/em/console/aboutApplication

DBCONSOLE already stopped...   Done.

Agent is already stopped...   Done.

Securing dbconsole...   Started.

Securing dbconsole...   Sucessful.

[oracle@DB-MASTER-1 ~]$ emctl status dbconsole

Oracle Enterprise Manager 11g Database Control Release 11.2.0.1.0 

Copyright (c) 1996, 2009 Oracle Corporation.  All rights reserved.

https://DB-MASTER-1:1158/em/console/aboutApplication

Oracle Enterprise Manager 11g is not running.

[oracle@DB-MASTER-1 ~]$ emctl start dbconsole

Oracle Enterprise Manager 11g Database Control Release 11.2.0.1.0 

Copyright (c) 1996, 2009 Oracle Corporation.  All rights reserved.

https://DB-MASTER-1:1158/em/console/aboutApplication

Starting Oracle Enterprise Manager 11g Database Control ..... started. 

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Logs are generated in directory /opt/oracle/product/11.2.0/db/db-master-1_orcl/sysman/log