This appendix  contains a checklist for Linux derived from the USE method. This is a method for checking system health, identifying common resource bottlenecks and errors, introduced in Chapter 2, Methodology. Later chapters (5, 6, 7, 9, 10) described it in specific contexts and introduced tools to support its use.
Performance tools are often enhanced and new ones are developed, so you should treat this as a starting point that will need updates. New observability frameworks and tools can also be developed to specifically make following the USE method easier.