How do you use the observer tool to inspect a running system?

observer is OTP's built-in GUI for peering into a live BEAM node: process list with memory and message queue length per process, supervision tree visualization, ETS table browser, and application overview, all without adding any extra code to the system being inspected.

1> observer:start().

Running that in a shell attached to (or connected to) the node you want to inspect opens the GUI. The Applications tab is often the fastest way to spot trouble: it renders the live supervision tree, so a worker stuck restarting in a crash loop, or a process with a mailbox that keeps growing, is visible at a glance rather than something you have to dig for with ad hoc shell commands.

For headless/remote servers without a GUI, the same information is available via shell functions like i/0, process_info/2, and ets:i/0, or via the newer observer_cli terminal-based alternative.

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