/opt/bitnami is the default directory for local installations if the installation was executed with sudo. If executed without sudo the ctlscript.sh can be found in the installation directory of the LAMP stack, which you have entered during the installation. Regarding the issue, it seems another MySQL process is running on 3306, you can find out which using the following command:
netstat -tulpn | grep 3306
and then kill it using:
kill -9 PID
Replacing PID with the actual PID number.
Then it should be possible to start the LAMP stack.
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