What is a Daemon. A daemon is a program running in the background without requiring user input. In Mac OS X, the Launch Daemons are stored inside /Library/LaunchDaemons/. Regarding all other abilities of the DAEMON Tools Lite for Mac OS X for free program, they are absolutely the same, and you may access them absolutely intuitively. You won’t need to get used to the interface of the utility, all the features are absolutely clear and transparent. I created a daemon for running into Mac OS X platform. I made an installer using PackageMaker and the Daemon is installed without problems. It seems that after the installation has finished, I need to reboot the system in order to have the daemon running. I am maintaining some OS X 10.10 machines which require cron for various tasks (watchdog processes, /tmp cleaners, etc.). One of them has mysteriously stopped its cron daemon, and I can't seem to bring it back up short of manually running the /usr/sbin/cron command as root.

In multitasking computer operating systems, a daemon (/ˈdiːmən/ or /ˈdeɪmən/)^[1] is a computer program that runs as a background process, rather than being under the direct control of an interactive user. Traditionally, the process names of a daemon end with the letter d, for clarification that the process is in fact a daemon, and for differentiation between a daemon and a normal computer program. For example, syslogd is a daemon that implements system logging facility, and sshd is a daemon that serves incoming SSH connections.

In a Unix environment, the parent process of a daemon is often, but not always, the init process. A daemon is usually created either by a process forking a child process and then immediately exiting, thus causing init to adopt the child process, or by the init process directly launching the daemon. In addition, a daemon launched by forking and exiting typically must perform other operations, such as dissociating the process from any controlling terminal (tty). Such procedures are often implemented in various convenience routines such as daemon(3) in Unix.

Systems often start daemons at boot time that will respond to network requests, hardware activity, or other programs by performing some task. Daemons such as cron may also perform defined tasks at scheduled times.

Terminology[edit]

The term was coined by the programmers at 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.^[2]Unix systems inherited this terminology. Maxwell's demon is consistent with Greek mythology's interpretation of a daemon as a supernatural being working in the background, with no particular bias towards good or evil. However, BSD and some of its derivatives have adopted a Christian demon as their mascot rather than a Greek daemon.^{[citation needed]}

The word daemon is an alternative spelling of demon,^[3] and is pronounced /ˈdiːmən/DEE-mən. In the context of computer software, the original pronunciation /ˈdiːmən/ has drifted to /ˈdeɪmən/DAY-mən for some speakers.^[1]

Alternate terms for daemon are service (used in Windows, from Windows NT onwards — and later also in Linux), started task (IBM z/OS),^[4] and ghost job (XDS UTS).

After the term was adopted for computer use, it was rationalized as a 'backronym' for Disk And Execution MONitor.^[5]

Daemons that connect to a computer network are examples of network services.

Implementations[edit]

Unix-like systems[edit]

In a strictly technical sense, a Unix-like system process is a daemon when its parent process terminates and the daemon is assigned the init process (process number 1) as its parent process and has no controlling terminal. However, more generally, a daemon may be any background process, whether a child of the init process or not.

On a Unix-like system, the common method for a process to become a daemon, when the process is started from the command line or from a startup script such as an init script or a SystemStarter script, involves:

• Optionally removing unnecessary variables from environment.
• Executing as a background task by forking and exiting (in the parent 'half' of the fork). This allows daemon's parent (shell or startup process) to receive exit notification and continue its normal execution.
• Detaching from the invoking session, usually accomplished by a single operation, setsid():
  • Dissociating from the controlling tty.
  • Creating a new session and becoming the session leader of that session.
  • Becoming a process group leader.
• If the daemon wants to ensure that it won't acquire a new controlling tty even by accident (which happens when a session leader without a controlling tty opens a free tty), it may fork and exit again. This means that it is no longer a session leader in the new session, and can't acquire a controlling tty.
• Setting the root directory (/) as the current working directory so that the process does not keep any directory in use that may be on a mounted file system (allowing it to be unmounted).
• Changing the umask to 0 to allow open(), creat(), and other operating system calls to provide their own permission masks and not to depend on the umask of the caller.
• Redirecting file descriptors 0, 1 and 2 for the standard streams (stdin, stdout and stderr) to /dev/null or a logfile, and closing all the other file descriptors inherited from the parent process.

If the process is started by a super-server daemon, such as {{mono|inetd{{mono|, launchd, or systemd, the super-server daemon will perform those functions for the process,^[6][7][8] except for old-style daemons not converted to run under systemd and specified as {{{1}}}^[8] and 'multi-threaded' datagram servers under inetd.^[6]

MS-DOS[edit]

Daemon For Mac Os Xp

In the Microsoft DOS environment, daemon-like programs were implemented as terminate and stay resident (TSR) software.

Windows NT[edit]

On Microsoft Windows NT systems, programs called Windows services perform the functions of daemons. They run as processes, usually do not interact with the monitor, keyboard, and mouse, and may be launched by the operating system at boot time. In Windows 2000 and later versions, Windows services are configured and manually started and stopped using the Control Panel, a dedicated control/configuration program, the Service Controller component of the Service Control Manager (sc command), the net start and net stop commands or the PowerShell scripting system.

However, any Windows application can perform the role of a daemon, not just a service, and some Windows daemons have the option of running as a normal process.

Classic Mac OS and macOS[edit]

On the classic Mac OS, optional features and services were provided by files loaded at startup time that patched the operating system; these were known as system extensions and control panels. Later versions of classic Mac OS augmented these with fully fledged faceless background applications: regular applications that ran in the background. To the user, these were still described as regular system extensions.

macOS, which is a Unix system, uses daemons. Note that macOS uses the term 'services' to designate software that performs functions selected from the Services menu, rather than using that term for daemons as Windows does.

Etymology[edit]

According to Fernando J. Corbató, who worked on Project MAC in 1963, his team was the first to use the term daemon, inspired by Maxwell's demon, an imaginary agent in physics and thermodynamics that helped to sort molecules, stating, 'We fancifully began to use the word daemon to describe background processes that worked tirelessly to perform system chores'.^[9]

Daemon For Mac Os X 10.13

In the general sense, daemon is an older form of the word 'demon', from the Greek δαίμων. In the Unix System Administration HandbookEvi Nemeth states the following about daemons:^[10]

Many people equate the word 'daemon' with the word 'demon', implying some kind of satanic connection between UNIX and the underworld. This is an egregious misunderstanding. 'Daemon' is actually a much older form of 'demon'; daemons have no particular bias towards good or evil, but rather serve to help define a person's character or personality. The ancient Greeks' concept of a 'personal daemon' was similar to the modern concept of a 'guardian angel'—eudaemonia is the state of being helped or protected by a kindly spirit. As a rule, UNIX systems seem to be infested with both daemons and demons.

A further characterization of the mythological symbolism is that a daemon is something that is not visible yet is always present and working its will. In the Theages, attributed to Plato, Socrates describes his own personal daemon to be something like the modern concept of a moral conscience: 'The favour of the gods has given me a marvelous gift, which has never left me since my childhood. It is a voice that, when it makes itself heard, deters me from what I am about to do and never urges me on'.^{[citation needed]}

See also[edit]

• Bounce message (also known as mailer daemon)

References[edit]

1. ^ ^abEric S. Raymond. 'daemon'. The Jargon File. Retrieved 2008-10-22.
2. ^Fernando J. Corbató (2002-01-23). 'Take Our Word for It'. Retrieved 2006-08-20.
3. ^'Merriam-Webster definition of daemon'. Merriam-Webster Online. Retrieved 2009-08-05.
4. ^'IBM Knowledge Center - Glossary of z/OS terms and abbreviations'. IBM.
5. ^'Daemon Definition'. www.linfo.org.
6. ^ ^abinetd(8) – FreeBSD System Manager's Manual
7. ^launchd.plist(5) – Darwin and macOS File Formats Manual
8. ^ ^ab'systemd.service'. freedesktop.org. Retrieved August 25, 2012.
9. ^'The Origin of the word Daemon'.
10. ^'The BSD Daemon'. Freebsd.org. Retrieved 2008-11-15.

External links[edit]

Being new to working on OS X, it has been somewhat confusing to how things work on Mac compared to that on Linux — to be completely honest it has been a painstaking journey while wrapping my head around the differences between the systems.

I intend to share my experience relating to adding start up shell scripts to the Launch Daemon on OS X Sierra. Any suggestions for a better solution is most welcome.

A good starting point to get to know about Launch Daemon Process — how to configure, troubleshoot and get some examples can be found here.

What is a Daemon

A daemon is a program running in the background without requiring user input.

1. Create an shell script file to start mariadb (for simplicity of demo)
2. Launch the shell script file as soon as the computer boots up (i.e. without requiring the user to login)

Step 1: Create an shell script file using the terminal

Now add in the following code to the file — save and exit. This primarily checks if the mariadb service is enabled or not and then starts the service if it is stopped.

Give the script file execution permission

Step 2: Launch the shell script file as soon as the computer boots up

We now have to add the script file to the Launch Daemon process — which will run the Job as soon as the Mac is booted.

Daemon For Mac Os X 10.10

Job Description

The behavior of a daemon/agent is specified in a special XML file called a property list. Depending on where it is stored it will be treated as a daemon or an agent.

Again, just to be clear between the difference between daemon/agents:

The main difference is that an agent is run on behalf of the logged in user while a daemon runs on behalf of the root user or any user you specify with the UserName key.

In Mac OS X, the Launch Daemons are stored inside

Daemon For Mac Os X64

folder while the Launch Agents are inside

Now, lets create a property list file(.plist) here as root user. (Please note there are conventions in naming the plist file which is outside the scope of this article)

Configuration of the plist file will vary upon your use case. The list of properties that can be configured is again nicely illustrated under the Configuration section on launchd.info

For easier illustration, please check the following plit file and the inline commets:

Now that we have all the necessary files ready and in place, we need to add the property list file onto the launchctl as follows:

Other notes,

• To permanently remove the plist to the Launch Daemon

• Once a script is added onto the Launch Daemon it will auto-start even if the user runs the following command

• A Gist with the source files is provided here.

That is it!

Do let me know if this works for you! Any suggestion for improvement will be most appreciated.