Daemon

Daemon is a type of computer program, either standalone or launched from another program, that runs in the background on a computer. It executes instructions to complete tasks that are not directly related to the user’s display but are important parts of the system’s daily operations. In this way, daemons provide a layer of continuous services to the operating system without the user or the program needing to constantly tend to them.

Daemons are found almost exclusively on Unix-like operating systems, including FreeBSD, Linux, Solaris, macOS, and IBM AIX. They are also found, with varying levels of compatibility, on non-Unix-like systems such as Windows, DOS, OS/2. The term daemon was first used in the early 1970s to describe non-interactive background scripts.

Daemons typically run continuously and without user intervention. Typically daemons handle system-related tasks such as managing printer queues, maintaining system logs, routing network traffic, or collecting usage statistics. They can also manage applications and services, such as web servers, FTP servers, mail servers, databases, and so on.

Daemons may also provide advanced services such as authentication, encryption, quota management, and network access. They are generally run by the root user, but some can be configured to run with reduced privileges. On Linux, daemons are usually started in the background by the init daemon. On macOS, they are typically started by launchd.

Daemons may also be started manually. For example, a Java Virtual Machine (JVM) can be started manually using the command java. The same process can be used to start any daemon that is available to the user.

There are a variety of ways in which daemons operate, dynamically changing the nature of the tasks that they take on based on system activity or user input. In some cases, daemons can be stopped or restarted on demand, allowing the user to upgrade components or reconfigure the daemon as desired. Furthermore, daemons can be programmed to control system resources and, in certain cases, even make decisions about which tasks should be handled when.