Synnefo » snf-ganeti

import resource

def Daemonize(logfile):

  """Daemonize the current process.

  This detaches the current process from the controlling terminal and

  runs it in the background as a daemon.

  """

  UMASK = 077

  WORKDIR = "/"

  # Default maximum for the number of available file descriptors.

  if 'SC_OPEN_MAX' in os.sysconf_names:

    try:

      MAXFD = os.sysconf('SC_OPEN_MAX')

      if MAXFD < 0:

        MAXFD = 1024

    except OSError:

      MAXFD = 1024

  else:

    MAXFD = 1024

  # this might fail

  pid = os.fork()

  if (pid == 0):  # The first child.

    os.setsid()

    # this might fail

    pid = os.fork() # Fork a second child.

    if (pid == 0):  # The second child.

      os.chdir(WORKDIR)

      os.umask(UMASK)

    else:

      # exit() or _exit()?  See below.

      os._exit(0) # Exit parent (the first child) of the second child.

  else:

    os._exit(0) # Exit parent of the first child.

  maxfd = resource.getrlimit(resource.RLIMIT_NOFILE)[1]

  if (maxfd == resource.RLIM_INFINITY):

    maxfd = MAXFD

  # Iterate through and close all file descriptors.

  for fd in range(0, maxfd):

    try:

      os.close(fd)

    except OSError: # ERROR, fd wasn't open to begin with (ignored)

      pass

  os.open(logfile, os.O_RDWR|os.O_CREAT|os.O_APPEND, 0600)

  # Duplicate standard input to standard output and standard error.

  os.dup2(0, 1)     # standard output (1)

  os.dup2(0, 2)     # standard error (2)

  return 0