Troubleshoot a crashed or unresponsive Linux server

A single web server has gone down, or it is up but requests hang. Walk through how you find the cause step by step and name the exact commands you would run at each step: checking whether the process is alive, its logs, CPU, memory, disk space and I/O, open connections, and recent changes.

Follow-ups include a disk that has filled up, slow responses caused by the database, how to see quickly what is running on the box, and how you would keep the server healthy over the following days.