100 Days of DevOps and Cloud (AWS), Day 11: A WAR File Deploys Itself, and an ENI Is a Network Card You Can Move

Short summary

Day 11 of a 100-day DevOps series covers two tasks: deploying a Java WAR file to Tomcat by simply copying it into the webapps directory, and attaching a secondary Elastic Network Interface to an EC2 instance for failover. The author explains that Tomcat auto-expands dropped WAR files and that ENIs carry their own IP, MAC, and security groups, making them portable network identities you can move between instances. Both tasks illustrate how deployment and networking complexity often shrinks once you understand the moving parts.

• •Deploy a WAR to Tomcat by copying it into the webapps directory—Tomcat auto-expands it
• •Attach a secondary ENI to EC2 for failover; ENIs carry IP, MAC, and security groups across instances
• •ENI and instance must be in the same availability zone

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