Overview
Applications launched by Passenger on v6+ platforms may emit output on stdout or stderr channels. Any output emitted is logged to an aggregate log called passenger.log in /var/log.
Important: since these logs are combined among all accounts using Passenger, never output anything confidential to stdout or stderr when launched using Passenger. Once an application is up and running, use a logging facility to log messages. Do not use a puts/print/console.log construct that will emit to stdout.
Sample output
App 24248 stdout: Migrations: Up to date at version 003 App 24248 stdout: Ghost is running... App 24248 stdout: Your blog is now available on http://my-ghost-blog.com App 24248 stdout: Ctrl+C to shut down App 24248 stdout: 64.22.68.22 - - [03/Mar/2015:20:10:12 +0000] "GET / HTTP/1.1" 200 3551 "-" "curl/7.29.0"
This is sample output from Ghost, a Node.js application. All output occurred over stdout and is likewise logged. Running Ghost from the command-line, e.g. node index.js would emit the same output.