A daemon is a long-running background process that answers requests for services. The term originated with Unix, but most operating systems use daemons in some form or another. In Unix, the names of daemons conventionally end in “d”. Some examples include inetd , httpd , nfsd , sshd , named , and lpd .
What is daemon used for?
A daemon (pronounced DEE-muhn) is a program that runs continuously and exists for the purpose of handling periodic service requests that a computer system expects to receive. The daemon program forwards the requests to other programs (or processes) as appropriate.
Why is it called a daemon in Linux?
The term was coined by the programmers of MIT’s Project MAC. They took the name from Maxwell’s demon, an imaginary being from a thought experiment that constantly works in the background, sorting molecules. Unix systems inherited this terminology.
How do I run a daemon in Linux?
This involves a few steps:
- Fork off the parent process.
- Change file mode mask (umask)
- Open any logs for writing.
- Create a unique Session ID (SID)
- Change the current working directory to a safe place.
- Close standard file descriptors.
- Enter actual daemon code.
Is Cron a daemon?
Cron is a daemon used to schedule any kind of task you can imagine. It is useful to send out emails on system or program statistics, do regular system maintenance, make backups, or do any task you can think of. There are similar programs on other Operating Systems.
How do I start a daemon process?
9 Answers
- fork off the parent process & let it terminate if forking was successful. …
- setsid – Create a new session. …
- Catch signals – Ignore and/or handle signals.
- fork again & let the parent process terminate to ensure that you get rid of the session leading process. …
- chdir – Change the working directory of the daemon.
What do you mean by daemon?
A daemon is a long-running background process that answers requests for services. The term originated with Unix, but most operating systems use daemons in some form or another. In Unix, the names of daemons conventionally end in “d”. Some examples include inetd , httpd , nfsd , sshd , named , and lpd .
Is a daemon a service?
Daemons are processes running in the background and are not in your face. They do certain tasks at set times or responds to certain events. In Windows, daemons are called services.
What is a daemon thread?
Daemon thread is a low priority thread that runs in background to perform tasks such as garbage collection. Properties: They can not prevent the JVM from exiting when all the user threads finish their execution. JVM terminates itself when all user threads finish their execution.
What’s the difference between a daemon and a service?
A daemon is a background, non-interactive program. It is detached from the keyboard and display of any interactive user. … A service is a program which responds to requests from other programs over some inter-process communication mechanism (usually over a network). A service is what a server provides.