[systemd-devel] How to run forking daemon with systemd in correct way, without errors?

[Reindl Harald]

Am 23.11.2017 um 10:32 schrieb Gena Makhomed:
> On 23.11.2017 7:45, Mantas Mikulėnas wrote:
> 
>>> This is bug in nginx code? And this bug should be fixed in nginx?
>>>
>>> But "daemon(); write_pidfile();" is common pattern
>>> used by many services and even in library functions.
> 
>> It may be common, but not necessarily correct. The parent process should
>> only exit *after* finishing all the preparations (i.e. something like
>> "fork(); write_pidfile(); exit()"), since systemd uses the exit as a 
>> signal
>> that the daemon is now "ready".
> 
> You are joking? Why you think that this pattern is not correct?

common sense

> Is any systemd documentations exists, which requires from daemons
> write pidfile of daemon process before exiting the parent process?
> 
> Does you see daemon() function from The GNU C Library (glibc)?
> It exits from parent process immediately, without writing pid file.
> Probably you should first fix function daemon() from glibc to meet 
> systemd requirements? And after this - rewrite all existing daemons?

well, if you want to tell the main-pid to systemd it's logical that 
there must be a defined point when that file exists, in most cases you 
don't need the PID stuff at all as i have explained multiple times

if you want so the daemon needs to write the pid file before telling 
systemd "i am ready"