Question

What would be the simplest way to daemonize a python script in Linux ? I need that this works with every flavor of Linux, so it should only use python based tools.

Answer 1

See Stevens and also this lengthy thread on activestate which I found personally to be both mostly incorrect and much to verbose, and I came up with this:

from os import fork, setsid, umask, dup2 from sys import stdin, stdout, stderr  if fork(): exit(0) umask(0)  setsid()  if fork(): exit(0)  stdout.flush() stderr.flush() si = file('/dev/null', 'r') so = file('/dev/null', 'a+') se = file('/dev/null', 'a+', 0) dup2(si.fileno(), stdin.fileno()) dup2(so.fileno(), stdout.fileno()) dup2(se.fileno(), stderr.fileno()) 

If you need to stop that process again, it is required to know the pid, the usual solution to this is pidfiles. Do this if you need one

from os import getpid outfile = open(pid_file, 'w') outfile.write('%i' % getpid()) outfile.close() 

For security reasons you might consider any of these after demonizing

from os import setuid, setgid, chdir from pwd import getpwnam from grp import getgrnam setuid(getpwnam('someuser').pw_uid) setgid(getgrnam('somegroup').gr_gid) chdir('/')  

You could also use nohup but that does not work well with python’s subprocess module