Welcome back to Linux Fundamentals. This is the first course in the Linux Foundation Specialization. In this module, we want to think about Linux services. By the time you're done with this module, when you take the quiz, you should be able to do these things: you should be able to list several services provided by the Linux operating system. You should be able to describe several web servers available in Linux. You should be able to describe several database servers available in Linux, and lastly, you should be able to start and stop services. In lesson 1, we want to distinguish between server and desktop. Servers focus on programs that provide shared resources, we call those services. Desktops focus on programs that run in a graphical user interface. We call that a GUI. Think about macOS and Windows, these are typical desktop operating systems. Now it's true, you might say Windows has server operating systems, it's true, but the GUI is really for the desktops. In this course, we're going to think about primarily the use of Linux as a server. We're going to think about these shared resources and services. There are two primary ways servers run service programs. The first is a background process that's always running listening for request. The other is as a process spawned by a parent program that listens for request. The parent is listening, a request comes in, it spins up a new child to service that request so that it can continue listening for new requests coming in from other clients. You're going to hear this term deamon referred to in services in Linux. What is a deamon? When a Linux service runs continually as a background process, it is called a deamon. Linux deamons often end with the letter d. For example, mysqld is the program that's a demon for the mysqld database. There are several major service types available. We have file servers, print servers, web servers, database servers, mail servers. Now, you all can think about the default name of a host on the web is www, that stands for web server. This comes from the days where in the office you would have a file server, often called file and a print server called print and web came along, which was World Wide Web, that was web server. We have all different kinds of servers, maybe a one machine, they may have separate machine, may have multiple machines to service the load. But we have these different major service types. We also have network resource servers. These are supplemental services that help support things like assigning addresses, logging, those sorts of things. A little review here. Linux desktop has programs designed around GUI interactive applications, graphical user interface. A Linux server has programs designed around background services that share resources, and deamons often end with the letter d in their name to help us see when it's running, that it's a deamon versus an interactive program. See you in the next lesson.
