Subject: Detach (daemon)

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Esben Stien - 27 Aug 2006 15:21 GMT

Any examples how to detach and run as a daemon?.

I've seen some use System.out.close() and System.err.close(), but I
just can't get it to detach and run as a daemon.

I'm on GNU/Linux, using gcj/classpath.

Any pointers?

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Gordon Beaton - 27 Aug 2006 18:33 GMT

> Any examples how to detach and run as a daemon?.
>
> I've seen some use System.out.close() and System.err.close(), but I
> just can't get it to detach and run as a daemon.
>
> I'm on GNU/Linux, using gcj/classpath.

The application doesn't need to do anything special, but you need to
run it like this from the shell (actual syntax may vary, but this
example assumes bash):

$ nohup java MyApp > /dev/null 2>&1 &

/gordon

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Esben Stien - 28 Aug 2006 02:11 GMT

> $ nohup java MyApp > /dev/null 2>&1 &

No. This is not what I'm looking for. This is a hack. I want the
application to detach cleanly like a normal daemon.

Thank you for your help so far, but this is not the correct way;).

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Gordon Beaton - 28 Aug 2006 07:55 GMT

>> $ nohup java MyApp > /dev/null 2>&1 &
>
> No. This is not what I'm looking for. This is a hack. I want the
> application to detach cleanly like a normal daemon.
>
> Thank you for your help so far, but this is not the correct way;).

A daemon changes its working directory, forks, redirects output
streams to /dev/null, detaches from the controlling terminal by
calling setsid(), and forks again. You'll be hard pressed to
accomplish most of that in Java.

Perhaps what you want is this instead:

$ setsid java MyApp > /dev/null 2>&1 &

or

$ ( setsid java MyApp > /dev/null 2>&1 & ) &

to get the extra fork.

If that isn't "clean enough" for you, then you need to write your own
Java launcher in C.

/gordon

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Domagoj Klepac - 28 Aug 2006 21:44 GMT

>> No. This is not what I'm looking for. This is a hack. I want the
>> application to detach cleanly like a normal daemon.
[quoted text clipped - 5 lines]
>calling setsid(), and forks again. You'll be hard pressed to
>accomplish most of that in Java.

When it comes to Java daemons/services:
http://wrapper.tanukisoftware.org/

Domchi

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Subject: Detach (daemon)

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