Linux Server Hacks, Volume Two

Chapter 8. Troubleshooting and Performance

Hacks 69–77: Introduction

You’d be amazed at how often “optimizing performance” really translates into “troubleshooting.” If something is misconfigured or otherwise broken, it’s likely that your first inkling that something is wrong is a result of poor performance, either of the service in question or the host on which it’s running.

Performance is a relative term. It’s important to know what a system looks like when it’s running under no load in order to be able to measure the impact of adding incrementally more users and services.

In this chapter, we’ll give you the tools and techniques to troubleshoot your way to better performance, to optimize resources the system reserves for its slated tasks, and to deal with resource hogs on your systems and networks.

Find Resource Hogs with Standard Commands

You don’t need fancy, third-party software or log analyzers to find and deal with a crazed user on a resource binge.

There are times when users will consume more than their fair share of system resources, be it CPU, memory, disk space, file handles, or network bandwidth. In environments where users are logging in on the console (or invoking the login utility by some other means), you can use pam_limits,or the ulimit utility to keep them from going overboard.

In other environments, neither of these is particularly useful. On development servers, for example, you could be hosting 50 developers on a single machine where they all test their code before ...