The default Ubuntu Dapper Drake installation includes some basic processes that check devices, tune the operating system, and perform housekeeping. Some of these processes are always running, while others start up periodically. Occasionally you might see your hard drive start up or grind away for a few minutes—what’s going on? On mission critical servers, serious gaming boxes, and other real-time systems, unexpected processes can cause huge problems; administrators should know exactly what is running and when. The last thing a time-sensitive application needs is for a resource-intensive maintenance system to start at an unexpected time and cause the system to slow down.

In order to fine-tune your system, you will need to know what is currently running, which resources are available, and when processes start up. From there, you can tweak configurations: disable undesirable processes, enable necessary housekeeping, and adjust your kernel to better handle your needs.

Time to Change
Different versions of Ubuntu (and Linux) use different startup scripts and run different support processes. Knowing how one version of Linux works does not mean that you know how all versions work. For example, one of my computers has a clock that loses a few minutes after every reboot. (It’s an old computer.) When I installed Ubuntu Dapper Drake (6.06), I noticed that the time was correct after a reboot. I started to look around to find out how it did that and which timeserver it was using. The first thing I noticed was that there was no script in /etc/init.d/ for setting the time. Eventually I tracked down the network startup scripts and found that the ntpdate script was moved from /etc/init.d/ (in previous Ubuntu releases) to /etc/network/if-up.d/. This script allowed me to find the network time protocol (NTP) configuration file (/etc/default/ntpdate).

A similar problem came up when I started running Ubuntu Hoary Hedgehog (5.04). Periodically the hard drives would grind when I was not doing anything. At other times it happened when I was running processes that were impacted by disk I/O—when the drives began to grind, the critical process would detect a processing problem. I quickly narrowed the disk grinding to updatedb—a caching program that works with slocate for quickly finding files. What I could not find was how this program was being started. Eventually I discovered that updatedb was started by anacron, an automated scheduler.

While it is important to know what is running, it is even more important to know how to track down running processes and tune them to your needs.

Learning the Lingo
Everything that runs on the system is a process. Processes are programs that perform tasks. The tasks may range from system maintenance to configuring plug-and-play devices and anything else the user needs. System processes manage keep the operating system running, whereas user processes handle user needs.

Many processes provide services for other processes. For example, a web server is a service for handling HTTP network requests. The web server may use one or more processes to perform its task. Some services are critical to the system’s operation. For example, if the system must support graphics but the X-Windows service is unavailable, then a critical service is missing.

Although most system processes are services, most user processes are applications. Applications consist of one or more processes for supporting user needs. For example, the Firefox web browser is an application that helps the user browse the web. In general, services start and end based on system needs, while applications start and end based on user needs.

None of these definitions—programs, processes, applications, and services—are very distinct. For example, the Gnome desktop consists of programs and processes that provide services to other programs and supports user needs. GDE can be called a set of programs, processes, applications, or services without any conflict.

When I talk about processes, I refer to anything that generates a running process identifier (see the next section for Viewing Running Processes). Programs are the executable files on the system that generate one or more processes. Users directly use applications, while the operating system uses services.

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