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thesharp / daemonize

daemonize is a library for writing system daemons in Python.
MIT License
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Why this lib doesnt fork twice? #63

Open coldfire-x opened 7 years ago

coldfire-x commented 7 years ago

Readed lots of posts, all mention we should fork twice for daemonize a py process, why this lib dont?

@penpen

Spectrik commented 6 years ago

I am wondering the same...

andy0130tw commented 5 years ago

Double fork is a technique meant to re-parent the daemon process to init. Some investigations show that it does not change its parent, as opposed to what we usually imagine a "daemon" would do.

For example, if you run the usage section of the doc, you may see:

$ ps j $(cat /tmp/test.pid)
 PPID   PID  PGID   SID TTY      TPGID STAT   UID   TIME COMMAND
 2091 21109 21109 21109 ?           -1 Ss    1000   0:00 python3 daemon.py

The number under PPID is the pid of the parent process. On my computer this is the pid of systemd daemon, not init:

$ ps 2091
  PID TTY      STAT   TIME COMMAND
 2091 ?        Ss     0:00 /lib/systemd/systemd --user

Strictly saying, I don't say the package is "daemonizing" the process. But thinking that it makes my script running in background is acceptable to me.