Fork - When a unix process creates a copy of itself.
Fork is an operation in Unix whereby a process creates a copy of itself. It is usually a system call, implemented in the kernel. Fork is the primary (and historically, only) method of process creation on Unix-like operating systems.
It’s a common technique used in Unix system programming.
Daemonizing a process involves the following 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 the actual daemon code.
For more information on daemons this guide is helpful.