What is capsule-daemon?

Capsule Daemon is a tool that lets you turn a Java application packaged as a "capsule" into a background service that runs on a server or desktop computer. Think of it like converting your app into the kind of service that starts automatically when the machine boots up, stays running in the background, and can be managed through the operating system's normal service controls, whether that's on Linux, Unix, or Windows. At a high level, it works by plugging into Capsule, which is a way of packaging Java applications as single self-contained files. The daemon component acts as an add-on that connects your capsule to platform-specific service managers. On Unix-like systems it uses a tool called jsvc, and on Windows it uses one called procrun, both of which are standard utilities for running Java apps as services. You can either build the daemon directly into your application package or run it alongside your app as a wrapper. It gives you control over things like which user account the service runs under, where it sends its log output, and how it should start and stop. This is useful for developers or teams shipping Java applications that need to run continuously on a server, like a web service or a database. For example, if you've built a Java web API and want it to start automatically on a Linux server after a reboot, this tool handles that setup without requiring you to manually write service configuration files. It's especially handy if you're already using Capsule packaging, since it integrates directly with that workflow. One thing to note is that setting it up requires some familiarity with how your target operating system manages services. On Unix, the default configuration needs administrator (root) access, and on Windows, you'll need administrative privileges to install or remove the service. The tool also doesn't support script-based capsules, which is a specific type of capsule packaging.