While reviewing instructions for Linux software, you may have come across mention of daemons. This somewhat obscure term is frequently used in reference to various pieces of utility software that allow your operating system to function properly. Everything from network management to file storage and resource usage is handled by these daemons, making them an integral part of any Linux-based personal computer or web server. As much of the work handled by daemons happens behind-the-scenes, it can be difficult to understand how to identify daemons and discern their functionality. In this article, we will discuss Linux daemons and provide some examples of common daemons in use today.
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What are Linux Daemons?
Linux Daemons, as mentioned previously, are pieces of utility software that manage the various services required by the operating system to function properly. The term was coined by MIT researchers who used the term “daemon” as a reference to Maxwell’s demon, an imaginary being that constantly works in the background sorting molecules.
This usage of daemon also appears in Greek mythology, where a daemon is a supernatural being that works in the background. While modern connotations of the word “demon” tend to imply ill intent, daemons as envisioned by Greek mythology were devoid of bias towards good or evil. In this sense, daemons are impartial entities that exist to perform a specific task.
Understanding the concept of daemons in this way makes it clear why the MIT researchers decided to use the term to describe software that exists to perform specific tasks within an operating system. These tasks include all essential functions of the operating system, such as managing SSH connections, DNS records, and facilitating network traffic. In the next section we will provide some examples of common Linux Daemons.
Examples of Linux Daemons
The most common way to identify a Linux daemon is to look for a service that ends with the letter d. We will provide some examples of these daemons below:
httpd – Daemon responsible for managing the HTTP service. Typically used with software such as Apache.
sshd – Daemon responsible for managing the SSH service. This is used on virtually any server that accepts SSH connections.
syslogd – Daemon responsible for managing system logging. This daemon ensures that all system logs are continuously updated with relevant information.
ftpd – Daemon responsible for managing the FTP service. This is used on most servers and personal computers, unless specifically disabled by the user.
crond – Daemon responsible for managing the cron service. The cron service acts as a scheduler for time-based actions such as software updates or system checks.
rlogind – Daemon responsible for managing the remote login service. This service allows users to log into the machine remotely.
All daemons run as background processes and do not require the direct intervention of a human operator, making them an invisible, yet vital, part of any Linux-based computer system. Now that you know how to identify daemons and understand what they do, it is clear why this obscure term is still relevant and in use today.