Application Migration and Docker‑Based Deployment Practices

Application migration across machines, data centers, and environments requires simplicity, speed, and lossless transfer.

The core of migration for a Tomcat‑based Java webapp is moving only the external configuration and data directories ( conf/ , webapps/ ) while keeping the immutable binary parts ( bin/ , lib/ ) unchanged.

Docker offers two deployment approaches: installing individual packages (similar to Juju) or packaging everything into a Docker image that includes the OS, Tomcat, and the application, enabling rapid rollout, rollback, and scaling.

Using Docker containers allows multiple isolated instances on a single host, and the layered filesystem separates base packages from mutable configuration, with CATALINA_BASE and CATALINA_HOME facilitating configuration isolation.

Configuration changes should be managed centrally—either by rebuilding and distributing updated images or by using a feature‑toggle platform or tools like Diamond for frequently changing settings.

Persistent or high‑write data such as logs/ , data/ should be stored in Docker volumes, declared with the VOLUME instruction in the Dockerfile.

Overall, a Docker‑centric operational model splits the application into base environment, dynamic configuration, and persistent data, enabling fast deployment, migration, updates, rollbacks, and scaling.

apache-tomcat-8.0.35/
├── bin/
├── conf/
├── lib/
├── logs/
├── temp/
├── webapps/
├── work/
├── LICENSE
├── NOTICE
├── RELEASE-NOTES
└── RUNNING.txt