[systemd-devel] removing daemon(0,0)

[Colin Guthrie]

'Twas brillig, and Michael D. Berger at 05/11/11 00:19 did gyre and gimble:
> 
>> -----Original Message-----
>> From: Michal Schmidt [mailto:mschmidt at redhat.com] 
>> Sent: Friday, November 04, 2011 17:45
>> To: Michael D. Berger
>> Cc: systemd-devel at lists.freedesktop.org
>> Subject: Re: [systemd-devel] FW: pthread_create() fails SysV 
>> in myDaemon on boot
>>
>> On Fri, 04 Nov 2011 14:36:05 -0400 Michael D. Berger wrote:
>>> Your assumption is correct.  In the code I have:
>>>       if (argc == 2)
>>>       {
>>>          string   arg = argv[1];
>>>          if (arg != "--daemon")
>>>             throw ...
>>>          ::daemon(0,0);
>>>          isDaemon = true;
>>>       }
>>
>> Not related to your problem with the cpu cgroup controller, but ...
>> daemon(3) is not the best way to daemonize a process. I 
>> suggest you to take a look at 
>> http://0pointer.de/public/systemd-man/daemon.html
>>
>> Michal
> 
> As you see, I made a new thread of this.
> 
> Looking at the recommended document, I concluded, perhaps
> incorrectly, that I should remove my
>    daemon(0,0);
> and add:
>    const char* const    state = "OK";
>    sd_notify(1/*unset_environment*/,state);
> 
> "man sd_notify" says the include file is
>    #include "sd-daemon.h"
> but the only one like this is:
>    #include </usr/share/doc/systemd/sd-daemon.h>
> I suuppose that I should have expected that ld can't find
> "sd-daemon", but I see:
>    /usr/share/doc/systemd/sd-daemon.c
> 
> Should I get it and compile it, or am I up the wrong tree?
> This is looking a little odd.

See man sd-notify:

       These APIs are implemented in the reference implementation's
       sd-daemon.c and sd-daemon.h files. These interfaces are available as
       shared library, which can be compiled and linked to with the
       libsystemd-daemon pkg-config(1) file. Alternatively, applications
       consuming these APIs may copy the implementation into their source
       tree, either verbatim or in excerpts.



> I tried just removing "daemon(0,0)", but
>    systemctl start myDaemon.service
> does not return, so it looked like sd_notify() might be 
> a good thing.

If you're app doesn't daemonise itself, then you can use a different
Type= in the unit file so systemd does this for you. In this case
Type=simple will do the job (or just leave Type out completely as this
is the default value).

Col




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Colin Guthrie
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