In this chapter, we’re going to explain services (programs running in the background as daemons) in more depth. We’re going to explain init scripts and systemd units. We are also going to cover Alpine Linux rc commands that manage services.
The chapter covers the following topics:
For this chapter, you will need a Linux system at hand where you can execute privileged commands, either using sudo or jumping straight to the root account (although we particularly recommend the first one). You’ll also need a Linux text editor of your choice that will produce pure text files. If you are going to edit on a Windows system, use a text editor that enables you to save Unix files. We recommend editing in the command line with one of your favorite command-line text editors: vim, emacs, joe, nano, or whatever suits you.
Unless you are running some kind of low-level embedded device on your desktop—and we strongly doubt it—your operating system manages a multitude of tasks to create a comfortable and productive environment for you. Be it Mac OS X, Linux, Windows, or FreeBSD, they all run a multitude of background programs that together provide a useful system. The same goes for server flavors of those operating systems. A background program or background process (in Unix and Linux called, fluffily, a daemon) means a program that is not attached to any input (keyboard, mouse, etc.) or output (monitor, terminal, etc.). This way, they can start working even when no one is logged in to the system and keep working when the user logs out. They can also run under the privileges of a user who can never log in to the system, making their execution much safer.
The number of services running on your Linux system will, in large part, depend on the distribution...
Upstart is an event-based replacement for the traditional SysV init system used to manage and control services and daemons on a system. Upstart was introduced in Ubuntu 6.10 and later versions and is designed to improve boot time, simplify system configuration, and provide more flexibility in managing system services. It has now been largely replaced by systemd in most Linux distributions.
Upstart is used to manage the initialization process of the system and to start, stop, and supervise tasks and services. It is designed to be more flexible and efficient than the traditional init daemon and to provide more information about the status of tasks and services.
All that can be managed by systemd and/or cron has become an industry standard, so if you don’t have a good reason for using those or already have a system using Upstart, we discourage you from using it as a default.
In this chapter, we covered system services—or daemons in the Unix and Linux world—and the software most often used to manage them. We explained what those are, how to inspect their state, and how to control them. In the next chapter, we are going to dive into Linux networking.
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