Problem: When starting emctl for first time after reboot on Linux, the following message appears:

Timezone mismatch: The agentTZRegion value (GMT) in /u01/app/oracle/product/10.2.0/db_1/localhost.localdomain_ORCL/sysman/config/emd.properties does not match the current environment TZ setting().

The dbconsole cannot run with this mismatch.

Solution:

Run:

emctl resetTZ agent

Then run:

emctl start dbconsole

You may need to stop the agent (but it says it is not running):

emctl stop agent