Computer Term: What is a Daemon?

If you deal a little with how a computer works or with the details of its operating system, you quickly stumble across the term "daemon". The term also appears from time to time in areas of pop culture that relate to computers and digitization. But what is a daemon actually? What is his job and what does the name actually mean? Here's an explanation and examples of a few important daemons on macOS.

What is a daemon on the computer and what is its role in the operating system? Which daemon on the Apple Mac starts macOS and which processes are involved? You can find answers to these and other questions here!
What is a daemon on the computer and what is its role in the operating system? Which daemon on the Apple Mac starts macOS and which processes are involved? You can find answers to these and other questions here!

What is a daemon?

A daemon is a background process that usually runs unnoticed and without direct interaction with the user on a computer or server. Daemons often perform automated tasks without requiring human intervention. In this way, system functions and services can be executed, settings loaded, network communication implemented and much more implemented. Daemons accompany the tasks from the start and monitor them in order to log the progress, detect errors, trigger a restart of the process if necessary, or end it when the task is complete.

Daemons are usually processes that run for a long time and are not tied to a user session. For example, they may be responsible for tasks such as network services (such as web servers, email servers, FTP servers), system monitoring, scheduling tasks (cron jobs), print management, and more. Daemons are usually designed to load automatically when the system starts up and work in the background without affecting the user experience. Under macOS, daemon management is also resource-saving, so that certain daemons are only loaded when they are needed - and not directly at system start.

Where does the name daemon come from?

Anyone who thinks that the background processes were named after devilish demons is wrong. They are not supposed to represent frightening spirits from hell, but rather messengers from heaven and the gods. Because the name "Demon" (for the time being without an a in it) was derived both from a thought experiment by the physicist James Clark Maxwells from the 19th century and from Greek mythology (there called δαίμων or Daimon). The invisible beings thus described serve as mediators between humans and gods. Similar to how they served as messengers between gods and humans, demons should act on the computer between the user and the operating system - invisibly and unnoticed.

In the course of development, however, people wanted to separate themselves from the religious-mystical meaning of the term. So Demon eventually became Daemon (with an a in it), and a backronym formed for it. This means that the word was subsequently used as an abbreviation for a word group attributed to it. For Daemon now the non-mythological, but more technical explanation Disk And Eexecution Mongiven to it. A daemon was thus declared advertised with disk and execution monitoring. In addition to this kind of description for a background service for backup tasks, a daemon can also fulfill other tasks, as already described above.

Launchd – The supreme messenger of the gods on macOS

Since Mac OS X 10.4 Tiger is used on the Apple Mac to start and run the operating system of the “launchd” daemon. launchd not only ensures that the operating system is started, but also that settings, configurations and background processes specified by the system and the user are loaded. Only then will the login screen be shown. launchd is the first process started directly by the kernel to have process ID 1. It also remains active while the system is running and performs various tasks - such as loading time-controlled processes (cron jobs). 

Examples of other daemons on macOS

You can recognize most daemons, for example in the process overview of the Activity indicator, on the "d" at the end of their name. This is the case with the "launchd" daemon, but also with its subordinate daemons. Here are a few examples of important macOS background processes that do not require direct user interaction but are important to users:

  • mdworker and mds: These processes are part of the macOS Spotlight search system. They are responsible for indexing files and metadata on the system to enable quick search and organization of files.
  • bluetoothd: The Bluetooth daemon manages the Bluetooth connectivity on the system. It enables pairing, connection, and communication between macOS devices and other Bluetooth-enabled devices.
  • cupsd: The "Common Unix Printing System Daemon" is responsible for managing the printing system on the Apple Mac. It allows printing to various printers, both local and on the network, as well as printing documents to a file (e.g. PDF).
  • opendirectoryd: This daemon manages the directory service on macOS, including user and group management and authentication. Among other things, he is responsible for folders shared on the network.
  • ssh agent: This daemon manages SSH key authentication and allows users to authenticate once for SSH connections without having to repeatedly enter the necessary passwords for them.

Is the finder a daemon?

No, that Finder-Process on Mac is not a daemon. It is the default file manager for macOS and represents the user interface for managing files, folders and applications. The Finder allows Mac users to browse, organize, open, copy and move files and folders. Daemons are typically background processes that manage specific system services or perform tasks without direct interaction with the people in front of the machine. The Finder, on the other hand, is an active component that allows users to interact with the file system and content on the computer.

Computer daemon summary

I hope I was able to explain the question of what a daemon is on the computer in an understandable way for you. If you use an Apple Mac, you should remember that Launchd is the first and foremost daemon of macOS. It loads the operating system and its configurations. Even before logging in, it locates system and user-specific daemons so that they are immediately available when logging in. However, others that are not required directly can also be loaded later if required, which leads to a higher efficiency of the system. Daemons ensure the operation and general usability of many functions, options, apps and tools during the use of operating systems. They are therefore essential components of the system.

(A source)

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