When a Linux server is slow, the order of the first commands matters more than the tools. A ten-minute triage routine that tells CPU, memory, disk and network pressure apart, what each column actually means, and the mistakes that send people down the wrong path.
When a server is slow and the dashboard is vague, a dozen standard commands narrow the problem to CPU, memory, disk, network or a single process in about five minutes. This is the order we run them in and how we read each output.
Requests on a reporting server took ten seconds every morning while CPU sat mostly idle. iowait at 60% pointed at storage; iostat and pidstat pointed at logrotate compressing a 40 GB log on the same volume as the database. How we found it and moved the work off the hot path.