I added .ebextensions/start.config
file to the root folder of my WAR bundle (as suggested by AWS), deployed it to Elastic Beanstalk, but nothing happened. Where in the EC2 instance can I see log of this file processing? Or maybe I can see this information in TAIL report of EBT?
Snapshot the Logs for your Elastic Beanstalk environment through the online console.
When you view the logs, search for a section beginning "cfn-init.log".
In that section you'll see entries like
2013-08-30 10:25:13,517 [INFO] Command 01-ec2setcomputername-enable succeeded
2013-08-30 10:25:24,516 [INFO] Command 02-install-server-monitor succeeded
2013-08-30 10:25:30,115 [INFO] Command 03-install-agent succeeded
where 01-ec2setcomputername-enable, etc. are the names of the commands in my .config file. If the command fails, you should see the error message here too.