Since this post has gotten a lot of attention over the years, I&#39;ve listed the top solutions per platform at the bottom of this post.

---

**Original post**:

I want my node.js server to run in the background, i.e.: when I close my terminal I want my server to keep running. I&#39;ve googled this and came up with this [tutorial][1], however it doesn&#39;t work as intended. So instead of using that daemon script, I thought I just used the output redirection (the `2&gt;&amp;1 &gt;&gt; file` part), but this too does not exit - I get a blank line in my terminal, like it&#39;s waiting for output/errors.

I&#39;ve also tried to put the process in the background, but as soon as I close my terminal the process is killed as well.

So how can I leave it running when I shut down my local computer?

---

**Top solutions**:

* [Systemd](https://stackoverflow.com/a/29042953/339122) (Linux)
* [Launchd](https://stackoverflow.com/a/25998406/339122) (Mac)
* [node-windows](https://stackoverflow.com/a/15616912/339122) (Windows)
* [PM2](https://stackoverflow.com/a/17005935/339122) (Node.js)

[1]: http://kevin.vanzonneveld.net/techblog/article/run_nodejs_as_a_service_on_ubuntu_karmic/


How do I run a node.js app as a background service?

I&#39;m trying to port a shell script to the much more readable python version. The original shell script starts several processes (utilities, monitors, etc.) in the background with &quot;&amp;&quot;. How can I achieve the same effect in python? I&#39;d like these processes not to die when the python scripts complete. I am sure it&#39;s related to the concept of a daemon somehow, but I couldn&#39;t find how to do this easily.

How to start a background process in Python?

What&#39;s the best way to run scheduled tasks in a Rails environment? Script/runner? Rake? I would like to run the task every few minutes.

A cron job for rails: best practices?

Let&#39;s assume we have such a trivial daemon written in python:

    def mainloop():
        while True:
            # 1. do
            # 2. some
            # 3. important
            # 4. job
            # 5. sleep
        
    mainloop()

and we daemonize it using `start-stop-daemon` which by default sends `SIGTERM` (`TERM`) signal on `--stop`.

Let&#39;s suppose the current step performed is `#2`. And at this very moment we&#39;re sending `TERM` signal.

What happens is that the execution terminates immediately.

I&#39;ve found that I can handle the signal event using `signal.signal(signal.SIGTERM, handler)` but the thing is that it still interrupts the current execution and passes the control to `handler`.

So, my question is - is it possible to not interrupt the current execution but handle the `TERM` signal in a separated thread (?) so that I was able to set `shutdown_flag = True` so that `mainloop()` had a chance to stop gracefully?

How to process SIGTERM signal gracefully?

In the [Python documentation][1]
it says:

&gt; A thread can be flagged as a &quot;daemon thread&quot;. The significance of this
&gt; flag is that the entire Python program exits when only daemon threads
&gt; are left. The initial value is inherited from the creating thread.

Does anyone have a clearer explanation of what that means or a practical example showing where you would set threads as `daemonic`?


Clarify it for me: so the only situation you wouldn&#39;t set threads as `daemonic`, is when you want them to continue running after the main thread exits?


  [1]: https://docs.python.org/2/library/threading.html#thread-objects

Daemon Threads Explanation

[Searching on Google][1] reveals x2 code snippets. The first result is to [this code recipe][2] which has a lot of documentation and explanation, along with some useful discussion underneath. 

However, [another code sample][3], whilst not containing so much documentation, includes sample code for passing commands such as start, stop and restart. It also creates a PID file which can be handy for checking if the daemon is already running etc.

These samples both explain how to create the daemon. Are there any additional things that need to be considered? Is one sample better than the other, and why?


  [1]: http://www.google.co.uk/search?q=python+daemon
  [2]: http://code.activestate.com/recipes/278731/
  [3]: https://gist.github.com/slor/5946334 

How do you create a daemon in Python?

I want to make a move to Docker, so I&#39;ve just started to mess around with it. I&#39;ve installed Docker on a VirtualBox Ubuntu 15.10 (Wily Werewolf) installation and as [suggested here][1] I then tried running a basic [nginx][2] Docker image:

    $ docker run --name mynginx1 -P -d nginx
    Cannot connect to the Docker daemon. Is the docker daemon running on this host?

So I checked out whether Docker was running:

    $ sudo service docker status
    ● docker.service - Docker Application Container Engine
       Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
       Active: active (running) since vr 2015-11-06 08:41:48 CET; 15min ago
         Docs: https://docs.docker.com
     Main PID: 7542 (docker)
       CGroup: /system.slice/docker.service
               └─7542 /usr/bin/docker daemon -H fd://
    
    nov 06 08:41:47 kramer65-VirtualBox systemd[1]: Starting Docker Application Container Engine...
    nov 06 08:41:47 kramer65-VirtualBox docker[7542]: time=&quot;2015-11-06T08:41:47.900410966+01:00&quot; level=info msg=&quot;API ...ock&quot;
    nov 06 08:41:48 kramer65-VirtualBox docker[7542]: time=&quot;2015-11-06T08:41:48.033514149+01:00&quot; level=info msg=&quot;Fire...lse&quot;
    nov 06 08:41:48 kramer65-VirtualBox docker[7542]: time=&quot;2015-11-06T08:41:48.141594321+01:00&quot; level=info msg=&quot;Defa...ess&quot;
    nov 06 08:41:48 kramer65-VirtualBox docker[7542]: time=&quot;2015-11-06T08:41:48.416294436+01:00&quot; level=warning msg=&quot;Y...it.&quot;
    nov 06 08:41:48 kramer65-VirtualBox docker[7542]: time=&quot;2015-11-06T08:41:48.565507576+01:00&quot; level=info msg=&quot;Load...rt.&quot;
    nov 06 08:41:48 kramer65-VirtualBox docker[7542]: time=&quot;2015-11-06T08:41:48.567907022+01:00&quot; level=info msg=&quot;Load...ne.&quot;
    nov 06 08:41:48 kramer65-VirtualBox docker[7542]: time=&quot;2015-11-06T08:41:48.567945214+01:00&quot; level=info msg=&quot;Daem...ion&quot;
    nov 06 08:41:48 kramer65-VirtualBox docker[7542]: time=&quot;2015-11-06T08:41:48.567969891+01:00&quot; level=info msg=&quot;Dock....9.0
    nov 06 08:41:48 kramer65-VirtualBox systemd[1]: Started Docker Application Container Engine.
    Hint: Some lines were ellipsized, use -l to show in full.

This suggests that the Docker daemon is actually already running, but to be sure I just started the Docker daemon manually:

    $ sudo docker daemon
    INFO[0000] API listen on /var/run/docker.sock           
    INFO[0000] [graphdriver] using prior storage driver &quot;aufs&quot; 
    INFO[0000] Firewalld running: false                     
    INFO[0000] Default bridge (docker0) is assigned with an IP address XXX.XX.X.X/XX. Daemon option --bip can be used to set a preferred IP address 
    WARN[0000] Your kernel does not support swap memory limit. 
    INFO[0000] Loading containers: start.                   
    
    INFO[0000] Loading containers: done.                    
    INFO[0000] Daemon has completed initialization          
    INFO[0000] Docker daemon                                 commit=76d6bc9 execdriver=native-0.2 graphdriver=aufs version=1.9.0

I then tried running the image again, but with the same result:

    $ docker run --name mynginx1 -P -d nginx
    Cannot connect to the Docker daemon. Is the docker daemon running on this host?

I tried sudo&#39;ing the command, but to no avail. What am I doing wrong here? 

  [1]: https://blog.docker.com/2015/04/tips-for-deploying-nginx-official-image-with-docker/
  [2]: http://en.wikipedia.org/wiki/Nginx




Docker command can&#39;t connect to Docker daemon

What is the best way to deploy Node.js?

I have a Dreamhost VPS (that&#39;s what they call a [VM][1]), and I have been able to install Node.js and set up a proxy. This works great as long as I keep the SSH connection that I started node with open.

  [1]: https://en.wikipedia.org/wiki/Virtual_machine


How do I run a Node.js application as its own process?

I&#39;m trying to create a daemon in python. I&#39;ve found the [following question][1], which has some good resources in it which I am currently following, but I&#39;m curious as to why a double fork is necessary. I&#39;ve scratched around google and found plenty of resources declaring that one is necessary, but not why.

Some mention that it is to prevent the daemon from acquiring a controlling terminal. How would it do this without the second fork? What are the repercussions?

  [1]: https://stackoverflow.com/questions/473620/how-do-you-create-a-daemon-in-python

What is the reason for performing a double fork when creating a daemon?

I need to run a php script as daemon process (wait for instructions and do stuff). cron job will not do it for me because actions need to be taken as soon as instruction arrives. I know PHP is not really the best option for daemon processes due to memory management issues, but due to various reasons I have to use PHP in this case. I came across a tool by libslack called Daemon (&lt;http://libslack.org/daemon&gt;) it seems to help me manage daemon processes, but there hasn&#39;t been any updates in the last 5 years, so I wonder if you know some other alternatives suitable for my case. Any information will be really appreciated.

Run php script as daemon process

In Linux I want to add a daemon that cannot be stopped and which monitors filesystem changes.
If any changes are detected, it should write the path to the console where it was started plus a newline.

I already have the filesystem changing code almost ready but I cannot figure out how to create a daemon.

My code is from here: http://www.yolinux.com/TUTORIALS/ForkExecProcesses.html

What to do after the fork?

    int main (int argc, char **argv) {
    
      pid_t pID = fork();
      if (pID == 0)  {              // child
              // Code only executed by child process    
          sIdentifier = &quot;Child Process: &quot;;
        }
        else if (pID &lt; 0) {
            cerr &lt;&lt; &quot;Failed to fork&quot; &lt;&lt; endl;
            exit(1);
           // Throw exception
        }
        else                                   // parent
        {
          // Code only executed by parent process
     
          sIdentifier = &quot;Parent Process:&quot;;
        }	    
    
        return 0;
    }


Creating a daemon in Linux

I want to use `ps -ef | grep &quot;keyword&quot;` to determine the pid of a daemon process (there is a unique string in output of ps -ef in it).

I can kill the process with `pkill keyword` is there any command that returns the pid instead of killing it? (pidof or pgrep doesnt work)

Getting pids from ps -ef |grep keyword

I have a python daemon running as a part of my web app/ How can I quickly check (using python) if my daemon is running and, if not, launch it?

I want to do it that way to fix any crashes of the daemon, and so the script does not have to be run manually, it will automatically run as soon as it is called and then stay running.

How can i check (using python) if my script is running?

Check to see if python script is running

My version of OS `Ubuntu 16.04`.
I want to stop docker, so I run in the terminal:

    sudo systemctl stop docker

But this commands doesn&#39;t help me:

    gridsim1103 ~: ps ax | grep docker 
    11347 ?        Sl     0:00 containerd-shim 487e3784f983274131d37bde1641db657e76e41bdd056f43ef4ad5adc1bfc518 /var/run/docker/libcontainerd/487e3784f983274131d37bde1641db657e76e41bdd056f43ef4ad5adc1bfc518 runc
    14299 pts/2    S+     0:00 grep --color=auto docker
    29914 ?        S      0:00 sudo dockerd -H gridsim1103:2376
    29915 ?        Sl     4:45 dockerd -H gridsim1103:2376
    29922 ?        Ssl    0:24 containerd -l unix:///var/run/docker/libcontainerd/docker-containerd.sock --shim containerd-shim --metrics-interval=0 --start-timeout 2m --state-dir /var/run/docker/libcontainerd/containerd --runtime runc
    30107 ?        Sl     1:01 /usr/bin/docker-proxy -proto tcp -host-ip 188.184.80.77 -host-port 8500 -container-ip 192.17.0.2 -container-port 8500
    30139 ?        Sl     0:00 /usr/bin/docker-proxy -proto tcp -host-ip 188.184.80.77 -host-port 8400 -container-ip 192.17.0.2 -container-port 8400

Version of `docker` server is:


    Server:
     Version:      1.12.1
     API version:  1.24 (minimum version )
     Go version:   go1.6.2
     Git commit:   23cf638
     Built:        Tue, 27 Sep 2016 12:25:38 +1300
     OS/Arch:      linux/amd64
     Experimental: false


I also unsuccessfully tried:

     sudo service docker stop


How to stop docker under Linux

Version of Android Studio (Beta) 0.8.4  
OS version: Windows 8  
Java JRE/JDK version: 1.8.0_11

    Error:Unable to start the daemon process.
    This problem might be caused by incorrect configuration of the daemon.
    For example, an unrecognized jvm option is used.
    Please refer to the user guide chapter on the daemon at http://gradle.org/docs/1.12/userguide/gradle_daemon.html
    -----------------------
    Error occurred during initialization of VM
    Could not reserve enough space for 1048576KB object heap
    Java HotSpot(TM) Client VM warning: ignoring option MaxPermSize=256m; support was removed in 8.0

Android Studio Gradle project &quot;Unable to start the daemon process /initialization of VM&quot;

I&#39;d like a daemonizer that can turn an arbitrary, generic script or command into a &lt;a href=&quot;http://en.wikipedia.org/wiki/Daemon_(computer_software)&quot;&gt;daemon&lt;/a&gt;.

There are two common cases I&#39;d like to deal with:

 1. I have a script that should run forever.  If it ever dies (or on reboot), restart it.  Don&#39;t let there ever be two copies running at once (detect if a copy is already running and don&#39;t launch it in that case).

 2. I have a simple script or command line command that I&#39;d like to keep executing repeatedly forever (with a short pause between runs).  Again, don&#39;t allow two copies of the script to ever be running at once.

Of course it&#39;s trivial to write a &quot;while(true)&quot; loop around the script in case 2 and then apply a solution for case 1, but a more general solution will just solve case 2 directly since that applies to the script in case 1 as well (you may just want a shorter or no pause if the script is not intended to ever die (of course if the script really *does* never die then the pause doesn&#39;t actually matter)).

Note that the solution should not involve, say, adding file-locking code or PID recording to the existing scripts.

More specifically, I&#39;d like a program &quot;daemonize&quot; that I can run like

    % daemonize myscript arg1 arg2

or, for example, 

    % daemonize &#39;echo `date` &gt;&gt; /tmp/times.txt&#39;

which would keep a growing list of dates appended to times.txt. (Note that if the argument(s) to daemonize is a script that runs forever as in case 1 above, then daemonize will still do the right thing, restarting it when necessary.)  I could then put a command like above in my .login and/or cron it hourly or minutely (depending on how worried I was about it dying unexpectedly).

NB: The daemonize script will need to remember the command string it is daemonizing so that if the same command string is daemonized again it does not launch a second copy.

Also, the solution should ideally work on both OS X and linux but solutions for one or the other are welcome.

EDIT: It&#39;s fine if you have to invoke it with `sudo daemonize myscript myargs`.

(If I&#39;m thinking of this all wrong or there are quick-and-dirty partial solutions, I&#39;d love to hear that too.)

&lt;hr&gt;

PS: In case it&#39;s useful, [here&#39;s](https://stackoverflow.com/questions/473620/how-do-you-create-a-daemon-in-python) a similar question specific to python.



And [this](https://stackoverflow.com/questions/38596/whats-the-best-way-to-keep-a-php-script-running-as-a-daemon/39609#39609) answer to a similar question has what appears to be a useful idiom for a quick-and-dirty demonizing of an arbitrary script:



How do I daemonize an arbitrary script in unix?

I have installed Jenkins executable on OSX, but now I want to stop it running. Whenever I kill it, no matter how, it just restarts immediately.

I&#39;ve tried using the exit command on the jenkins url:

    http://localhost:8080/exit

which asks me to post the command, which I do, and the server shuts down as requested. *But then it restarts.*

I&#39;ve tried searching for the process id using `ps`, and force killing it (`kill -9 pid`), and the server shuts down immediately, as requested. *But then it restarts.*

I&#39;ve tried shutting it down via the gui, but unfortunately there doesn&#39;t seem to be a way to do that.

There must be a daemon somewhere, making this a general OSX question. 

How to stop Jenkins installed on Mac Snow Leopard?

I&#39;m wondering if there is a better way to make a daemon that waits for something using only sh than:

    #! /bin/sh
    trap processUserSig SIGUSR1
    processUserSig() {
      echo &quot;doing stuff&quot;
    }
    
    while true; do
      sleep 1000
    done

In particular, I&#39;m wondering if there&#39;s any way to get rid of the loop and still have the thing listen for the signals.


Best way to make a shell script daemon?

I have a Java program that I&#39;d like to daemonize on a linux system. In other words, I want to start running it in a shell and have it continue running after I&#39;ve logged out. I also want to be able to stop the program cleanly.

I found [this article][1] which uses a combination of shell scripting and Java code to do the trick. It looks good, but I&#39;d like something simpler, if possible.

What&#39;s your preferred method to daemonize a Java program on a Linux system?


  [1]: http://barelyenough.org/blog/2005/03/java-daemon/ &quot;this article&quot;

How to Daemonize a Java Program?

This is my first web-server administration experience and I want to build docker container which uses nginx as a web-server. In all docker tutorial `daemon off;` option is put into main `.conf` file but explanation about it is omitted.

I search on the internet about it and I don&#39;t understand what is the difference between `daemon on;` and `daemon off;` options. Some people mentioned that `daemon off;` is for production, why?

Can you explain, what is the difference between this two options, and why I should use `daemon off;` on production?

What is the difference between nginx daemon on/off option?

I&#39;m a little confused about what setting a thread to be a daemon means. 

The documentation says this:

&gt; A thread can be flagged as a “daemon
&gt; thread”. The significance of this flag
&gt; is that the entire Python program
&gt; exits when only daemon threads are
&gt; left. The initial value is inherited
&gt; from the creating thread. The flag can
&gt; be set through the daemon property.

I&#39;m not sure what makes this different from a normal thread. 

Is this saying that this program won&#39;t ever finish?

    def threadfunc():
        while True:
            time.sleep(1)
    
    threading.Thread(target=threadfunc).start()

Even though the main thread finishes it&#39;s execution. While will finish immediately?


    def threadfunc():
        while True:
            time.sleep(1)
    
    th = threading.Thread(target=threadfunc)
    th.daemon = True
    th.start()


I ask because I have a situation where in my main thread I&#39;m calling sys.exit(), and the process just hangs and my other threads are running as I can see the log. 

Does this have anything to do with sys.exit() being called with threads alive?





Meaning of daemon property on Python Threads

Hallo,

I&#39;m trying to let a python script run as service (daemon) on (ubuntu) linux.

On the web there exist several solutions like:

http://pypi.python.org/pypi/python-daemon/

&gt; A well-behaved Unix daemon process is tricky to get right, but the required steps are much the same for every daemon program. A DaemonContext instance holds the behaviour and configured process environment for the program; use the instance as a context manager to enter a daemon state.

http://www.jejik.com/articles/2007/02/a_simple_unix_linux_daemon_in_python/

However as I want to integrate my python script specifically with ubuntu linux my solution is a combination with an init.d script

    #!/bin/bash

    WORK_DIR=&quot;/var/lib/foo&quot;
    DAEMON=&quot;/usr/bin/python&quot;
    ARGS=&quot;/opt/foo/linux_service.py&quot;
    PIDFILE=&quot;/var/run/foo.pid&quot;
    USER=&quot;foo&quot;

    case &quot;$1&quot; in
      start)
        echo &quot;Starting server&quot;
        mkdir -p &quot;$WORK_DIR&quot;
        /sbin/start-stop-daemon --start --pidfile $PIDFILE \
            --user $USER --group $USER \
            -b --make-pidfile \
            --chuid $USER \
            --exec $DAEMON $ARGS
        ;;
      stop)
        echo &quot;Stopping server&quot;
        /sbin/start-stop-daemon --stop --pidfile $PIDFILE --verbose
        ;;
      *)
        echo &quot;Usage: /etc/init.d/$USER {start|stop}&quot;
        exit 1
        ;;
    esac

    exit 0

and in python:

    import signal
    import time
    import multiprocessing

    stop_event = multiprocessing.Event()

    def stop(signum, frame):
        stop_event.set()

    signal.signal(signal.SIGTERM, stop)

    if __name__ == &#39;__main__&#39;:
        while not stop_event.is_set():
            time.sleep(3)

My question now is if this approach is correct. Do I have to handle any additional signals? Will it be a &quot;well-behaved Unix daemon process&quot;?

Python script as linux service/daemon

I&#39;m new to Docker, using Boot2Docker on OSX. After booting it, this message is given:

    To connect the Docker client to the Docker daemon, please set
    export DOCKER_HOST=tcp://192.168.59.103:2375

Yet even without it, basic Docker commands (eg, `docker run hello-world`) work fine.

The install instructions aren&#39;t very informative:

    Note: If you see a message in the terminal that looks something like this:
    To connect the Docker client to the Docker daemon, please set: 
    export  DOCKER_HOST=tcp://192.168.59.103:2375
    you can safely set the evironment variable as instructed.

Knowing that it&#39;s &quot;safe&quot; doesn&#39;t say why it&#39;s useful.

What I&#39;m not clear on:

1. What is the docker &quot;client&quot;?
2. What is the docker &quot;daemon&quot;?
3. What is the docker &quot;host&quot;? (The Boot2Docker VM itself?)



What does the DOCKER_HOST variable do?

I am trying to understand how can I make my program a daemon.So some things which I came across are In general, a program performs the following steps to become a daemon:  

1. Call `fork( )`. 
2. In the parent, call `exit( )`. This ensures that the original parent (the daemon&#39;s
grandparent) is satisfied that its child terminated, that the daemon&#39;s parent is no
longer running, and that the daemon is not a process group leader. This last point
is a requirement for the successful completion of the next step.  

3. Call `setsid( )`, giving the daemon a new process group and session, both of
  which have it as leader. This also ensures that the process has no associated
  controlling terminal (as the process just created a new session, and will not assign
  one).

4. Change the working directory to the root directory via `chdir( )`. This is done
because the inherited working directory can be anywhere on the filesystem.
Daemons tend to run for the duration of the system&#39;s uptime, and you don&#39;t want
to keep some random directory open, and thus prevent an administrator from
unmounting the filesystem containing that directory.

5. Close all file descriptors. 
6. Open file descriptors 0, 1, and 2 (standard in, standard out, and standard error)
and redirect them to `/dev/null`.


&lt;pre&gt;&lt;code&gt;#include &amp;lt;sys/types.h&amp;gt;
#include &amp;lt;sys/stat.h&amp;gt;
#include &amp;lt;stdlib.h&amp;gt;
#include &amp;lt;stdio.h&amp;gt;
#include &amp;lt;fcntl.h&amp;gt;
#include &amp;lt;unistd.h&amp;gt;
#include &amp;lt;linux/fs.h&amp;gt;

int main (void)
{
    pid_t pid;
    int i;
    
    /* create new process */
    pid = fork ( );  
    if (pid == -1)  
        return -1;  
    else if (pid != 0)  
        exit (EXIT_SUCCESS);  

    /* create new session and process group */  
    if (setsid ( ) == -1)  
        return -1;  

    /* set the working directory to the root directory */  
    if (chdir (&quot;/&quot;) == -1)  
        return -1;  

    /* close all open files--NR_OPEN is overkill, but works */  
    for (i = 0; i &amp;lt; NR_OPEN; i++)  
        close (i);  

    /* redirect fd&#39;s 0,1,2 to /dev/null */  
    open (&quot;/dev/null&quot;, O_RDWR);  
    /* stdin */  
    dup (0);  
    /* stdout */  
    dup (0);  
    /* stderror */  
    
    /* do its daemon thing... */  
    
    return 0;  
}&lt;/code&gt;&lt;/pre&gt;  



Can some one give me a link to existing source code of some program like Apache so that I can understand this process in more depth.


how to make a process daemon

So I have a daemon running on a Linux system, and I want to have a record of its activities: a log. The question is, what is the &quot;best&quot; way to accomplish this?

My first idea is to simply open a file and write to it.

    FILE* log = fopen(&quot;logfile.log&quot;, &quot;w&quot;);
    /* daemon works...needs to write to log */
    fprintf(log, &quot;foo%s\n&quot;, (char*)bar);
    /* ...all done, close the file */
    fclose(log);

Is there anything inherently wrong with logging this way? Is there a better way, such as some framework built into Linux?

Daemon logging in Linux

What are the implications of running a script as a daemon versus using nohup?

I know what the difference is in terms of forking processes etc., but what impact does that have on my script?

What&#39;s the difference between nohup and a daemon?

I&#39;ve a long running server written in Go.  Main fires off several goroutines where the logic of the program executes.  After that main does nothing useful.  Once main exits, the program will quit.  The method I am using right now to keep the program running is just a simple call to fmt.Scanln().  I&#39;d like to know how others keep main from exiting.  Below is a basic example.  What ideas or best practices could be used here?

I considered creating a channel and delaying exit of main by receiving on said channel, but I think that could be problematic if all my goroutines become inactive at some point.

Side note:  In my server (not the example), the program isn&#39;t actually running connected to a shell, so it doesn&#39;t really make sense to interact with the console anyway.  For now it works, but I&#39;m looking for the &quot;correct&quot; way, assuming there is one.

    package main

    import (
        &quot;fmt&quot;
        &quot;time&quot;
    )
    
    func main() {
        go forever()
        //Keep this goroutine from exiting
        //so that the program doesn&#39;t end.
        //This is the focus of my question.
        fmt.Scanln()
    }

    func forever() {
        for ; ; {
        //An example goroutine that might run
        //indefinitely. In actual implementation
        //it might block on a chanel receive instead
        //of time.Sleep for example.
            fmt.Printf(&quot;%v+\n&quot;, time.Now())
            time.Sleep(time.Second)
        }
    }

How best do I keep a long running Go program, running?

Where can I find a **well-respected reference** that details the proper handling of PID files on Unix?

On Unix operating systems, it is common practice to “lock” a program (often a daemon) by use of a special lock file: the PID file.

This is a file in a predictable location, often ‘/var/run/foo.pid’. The program is supposed to check when it starts up whether the PID file exists and, if the file does exist, exit with an error. So it&#39;s a kind of advisory, collaborative locking mechanism.

The file contains a single line of text, being the numeric process ID (hence the name “PID file”) of the process that currently holds the lock; this allows an easy way to automate sending a signal to the process that holds the lock.

What I can&#39;t find is a good reference on expected or “best practice” behaviour for handling PID files. There are various nuances: how to actually lock the file (don&#39;t bother? use the kernel? what about platform incompatibilities?), handling stale locks (silently delete them? when to check?), when exactly to acquire and release the lock, and so forth.

Where can I find a **respected, most-authoritative reference** (ideally on the level of W. Richard Stevens) for this small topic?


Reference for proper handling of PID file on Unix

What&#39;s a simple way to get a Perl script to run as a daemon in linux?

Currently, this is on CentOS. I&#39;d want it to start up with the system and shutdown with the system, so some `/etc/rc.d/init.d` integration would also be nice, but I could always add a custom line to `/etc/rc.d/rc.local`.


How can I run a Perl script as a system daemon in linux?

How can I run a shell script and immediately *background* it, however keep the ability to inspect its output any time by tailing `/tmp/output.txt`.

It would be nice if I can *foreground* the process too later.

---
### P.S.  
It would be really cool if you can also show me how to &quot;send&quot; the backgrounded process in to a GNU screen that may or may not have been initialized.

Run a shell script and immediately background it, however keep the ability to inspect its output

I would like to run multi-container application using `docker-compose` on Mac OS X El Capitan (v10.11.2).

However, the command `$ docker-compose up` command complains that it can&#39;t connect to the Docker daemon.

&gt; ERROR: Couldn&#39;t connect to Docker daemon - you might need to run `docker-machine start default`.

Only after executing `$ eval &quot;$(docker-machine env default)&quot;` I do have access to the `docker-compose` command.

Why is this and how can I overcome this extra step?

Couldn&#39;t connect to Docker daemon on Mac OS X

I&#39;m facing the below error when I&#39;m trying to import a gradle project in Android Studio.
 
    Unable to start the daemon process.
    This problem might be caused by incorrect configuration of the daemon.
    For example, an unrecognized jvm option is used.
    Please refer to the user guide chapter on the daemon at http://gradle.org/docs/1.8/userguide/gradle_daemon.html
    Please read below process output to find out more: 

and this is the output I see:

    18:25:42.484 [main] DEBUG o.g.l.daemon.bootstrap.DaemonMain - Assuming the daemon was started with following jvm opts: [-XX:MaxPermSize=256m, -XX:+HeapDumpOnOutOfMemoryError, -Xmx1024m, -Dfile.encoding=windows-1252]
    18:25:43.254 [main] DEBUG o.g.l.daemon.server.DaemonServices - Creating daemon context with opts: [-XX:MaxPermSize=256m, -XX:+HeapDumpOnOutOfMemoryError, -Xmx1024m, -Dfile.encoding=windows-1252]
    18:25:43.306 [DEBUG] [org.gradle.logging.internal.DefaultLoggingConfigurer] Finished configuring with level: DEBUG, configurers: [org.gradle.logging.internal.OutputEventRenderer@47078ad, org.gradle.logging.internal.logback.LogbackLoggingConfigurer@7402a821, org.gradle.logging.internal.JavaUtilLoggingConfigurer@5a6c4a07]
    18:25:43.356 [INFO] [org.gradle.launcher.daemon.server.Daemon] start() called on daemon - DefaultDaemonContext[uid=e58252c1-7a49-4be4-a6cd-1bd3d6d0880d,javaHome=C:\Program Files\Java\jdk1.7.0_45,daemonRegistryDir=C:\Users\Sowmya\.gradle\daemon,pid=15432,idleTimeout=60000,daemonOpts=-XX:MaxPermSize=256m,-XX:+HeapDumpOnOutOfMemoryError,-Xmx1024m,-Dfile.encoding=windows-1252]
    18:25:43.362 [DEBUG] [org.gradle.launcher.daemon.server.DaemonStateCoordinator] updating lastActivityAt to 1386593743362
    18:25:43.702 [DEBUG] [org.gradle.messaging.remote.internal.inet.InetAddressFactory] Adding IP addresses for network interface lo
    18:25:43.705 [DEBUG] [org.gradle.messaging.remote.internal.inet.InetAddressFactory] Is this a loopback interface? true
    18:25:43.706 [DEBUG] [org.gradle.messaging.remote.internal.inet.InetAddressFactory] Adding loopback address /127.0.0.1
    18:25:43.707 [DEBUG] [org.gradle.messaging.remote.internal.inet.InetAddressFactory] Adding loopback address /0:0:0:0:0:0:0:1
    18:25:43.708 [DEBUG] [org.gradle.messaging.remote.internal.inet.InetAddressFactory] Adding IP addresses for network interface net0
    18:25:43.711 [DEBUG] [org.gradle.messaging.remote.internal.inet.InetAddressFactory] Is this a loopback interface? false
    DefaultDaemonContext[uid=e58252c1-7a49-4be4-a6cd-1bd3d6d0880d,javaHome=C:\Program Files\Java\jdk1.7.0_45,daemonRegistryDir=C:\Users\Sowmya\.gradle\daemon,pid=15432,idleTimeout=60000,daemonOpts=-XX:MaxPermSize=256m,-XX:+HeapDumpOnOutOfMemoryError,-Xmx1024m,-Dfile.encoding=windows-1252]
    18:25:43.951 [DEBUG] [org.gradle.cache.internal.DefaultFileLockManager] Waiting to acquire exclusive lock on daemon addresses registry.
    18:25:43.954 [DEBUG] [org.gradle.cache.internal.DefaultFileLockManager] Lock acquired.
    18:25:43.957 [DEBUG] [org.gradle.cache.internal.DefaultFileLockManager] Releasing lock on daemon addresses registry.
    18:25:43.962 [DEBUG] [org.gradle.cache.internal.DefaultFileLockManager] Waiting to acquire exclusive lock on daemon addresses registry.
    18:25:43.963 [DEBUG] [org.gradle.cache.internal.DefaultFileLockManager] Lock acquired.
    18:25:43.966 [DEBUG] [org.gradle.cache.internal.DefaultFileLockManager] Releasing lock on daemon addresses registry.
    18:25:43.976 [ERROR] [system.err] 
    18:25:43.977 [ERROR] [system.err] FAILURE: Build failed with an exception.
    18:25:43.977 [ERROR] [system.err] 
    18:25:43.978 [ERROR] [system.err] * What went wrong:
    18:25:43.979 [ERROR] [system.err] Could not write cache value to &#39;C:\Users\Sowmya\.gradle\daemon\1.8\registry.bin&#39;.
    18:25:43.979 [ERROR] [system.err] 
    18:25:43.980 [ERROR] [system.err] * Try:
    18:25:43.981 [ERROR] [system.err] Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
    18:25:44.009 [INFO] [org.gradle.launcher.daemon.bootstrap.DaemonMain] Daemon[pid = 15432] process has finished.
    18:25:44.010 [DEBUG] [org.gradle.launcher.daemon.registry.PersistentDaemonRegistry] Removing daemon address: [9ae053cd-4dc2-4cb8-8f60-bb3c5983eb67 port:55117, addresses:[/127.0.0.1, /0:0:0:0:0:0:0:1]]
    18:25:44.011 [DEBUG] [org.gradle.cache.internal.DefaultFileLockManager] Waiting to acquire exclusive lock on daemon addresses registry.
    18:25:44.012 [DEBUG] [org.gradle.cache.internal.DefaultFileLockManager] Lock acquired.
    18:25:44.013 [DEBUG] [org.gradle.cache.internal.DefaultFileLockManager] Releasing lock on daemon addresses registry.
    18:25:44.014 [DEBUG] [org.gradle.cache.internal.DefaultFileLockManager] Waiting to acquire exclusive lock on daemon addresses registry.
    18:25:44.015 [DEBUG] [org.gradle.cache.internal.DefaultFileLockManager] Lock acquired.
    18:25:44.016 [DEBUG] [org.gradle.cache.internal.DefaultFileLockManager] Releasing lock on daemon addresses registry.
    18:25:44.021 [DEBUG] [org.gradle.launcher.daemon.server.Daemon] VM shutdown hook was unable to remove the daemon address from the registry. It will be cleaned up later.
    org.gradle.api.GradleException: Could not write cache value to &#39;C:\Users\Sowmya\.gradle\daemon\1.8\registry.bin&#39;.
    	at org.gradle.cache.internal.SimpleStateCache.serialize(SimpleStateCache.java:74)
    	at org.gradle.cache.internal.SimpleStateCache.access$100(SimpleStateCache.java:28)
    	at org.gradle.cache.internal.SimpleStateCache$2.run(SimpleStateCache.java:50)
    	at org.gradle.cache.internal.DefaultFileLockManager$DefaultFileLock.doWriteAction(DefaultFileLockManager.java:198)
    	at org.gradle.cache.internal.DefaultFileLockManager$DefaultFileLock.writeFile(DefaultFileLockManager.java:187)
    	at org.gradle.cache.internal.OnDemandFileAccess.writeFile(OnDemandFileAccess.java:58)
    	at org.gradle.cache.internal.SimpleStateCache.set(SimpleStateCache.java:48)
    	at org.gradle.cache.internal.FileIntegrityViolationSuppressingPersistentStateCacheDecorator.set(FileIntegrityViolationSuppressingPersistentStateCacheDecorator.java:38)
    	at org.gradle.cache.internal.FileIntegrityViolationSuppressingPersistentStateCacheDecorator.update(FileIntegrityViolationSuppressingPersistentStateCacheDecorator.java:46)
    	at org.gradle.launcher.daemon.registry.PersistentDaemonRegistry.remove(PersistentDaemonRegistry.java:109)
    	at org.gradle.launcher.daemon.server.Daemon$1.run(Daemon.java:100)
    Caused by: java.io.FileNotFoundException: C:\Users\Sowmya\.gradle\daemon\1.8\registry.bin (Access is denied)
    	at java.io.FileOutputStream.open(Native Method)
    	at java.io.FileOutputStream.&lt;init&gt;(FileOutputStream.java:221)
    	at java.io.FileOutputStream.&lt;init&gt;(FileOutputStream.java:171)
    	at org.gradle.cache.internal.SimpleStateCache.serialize(SimpleStateCache.java:67)
    	... 10 more`

I&#39;ve turned off my anti-virus which was mentioned in a solution in SO. But nothing seems to work. 




Android Studio: Unable to start the daemon process

I wrote a small Python application that runs as a daemon. It utilizes threading and queues. 

I&#39;m looking for general approaches to altering this application so that I can communicate with it while it&#39;s running. Mostly I&#39;d like to be able to monitor its health.

In a nutshell, I&#39;d like to be able to do something like this:

    python application.py start  # launches the daemon

Later, I&#39;d like to be able to come along and do something like:

    python application.py check_queue_size  # return info from the daemonized process

To be clear, I don&#39;t have any problem implementing the Django-inspired syntax. What I don&#39;t have any idea how to do is to send signals to the daemonized process (start), or how to write the daemon to handle and respond to such signals.

Like I said above, I&#39;m looking for general approaches. The only one I can see right now is telling the daemon constantly log everything that might be needed to a file, but I hope there&#39;s a less messy way to go about it.

**UPDATE:** Wow, a lot of great answers. Thanks so much. I think I&#39;ll look at both Pyro and the web.py/Werkzeug approaches, since Twisted is a little more than I want to bite off at this point. The next conceptual challenge, I suppose, is how to go about talking to my worker threads without hanging them up.

Thanks again.

Communicating with a running python daemon

I&#39;m trying to write a Mono C# daemon for linux.

I&#39;d like to do a starts and stops of it when its done processing instead of just killing the process.

Does anyone have any examples of this?

Edit: I figured out how to use start-stop-daemon --background in debian, so I think I&#39;ll just use that for now.

Edit: I&#39;m implementing this in java as well and they have this nice addShutdownHook that catches terminating the app. I need to spend a little more time sorting out the dependencies for mono service, or find a way to catch app termination. 

There is the SessionEnd event, but thats only available for services and not console apps

**Answer:**
[using mono-service to wrap a windows service on linux][1]


  [1]: https://stackoverflow.com/questions/351971/using-mono-service-to-wrap-a-windows-service-on-linux

How do I code a Mono Daemon

I am writing a Linux daemon . I found two ways to do it.

1. Daemonize your process by calling `fork()` and setting `sid`.
2. Running your program with `&amp;`.

Which is the right way to do it?

Linux daemonize

I have recently completed the *Wiki web development tutorial* ([http://golang.org/doc/articles/wiki/][1]). I had tons of fun and I would like to experiment more with the net/http package.

However, I noticed that when I run the wiki from a console, the wiki takes over the console. If I close the console terminal or stop the process with &lt;kbd&gt;CTRL+Z&lt;/kbd&gt; then the server stops.

How can I get the server to run in the background? I think the term for that is running in a daemon.

I&#39;m running this on Ubuntu 12.04. Thanks for any help.


  [1]: http://golang.org/doc/articles/wiki/

All Daemon Solutions on Gang of Coders

Total of 36 Daemon Solutions