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Bugus on fork processing

Browse Source 
http://linux.die.net/man/1/daemonize

Need only 1 fork

Close all standard descriptor in main process  
Change directory on main process
Reset umask  on main process

Fork 
exit main process
detach and attache init
This commit is contained in:
perl5577 2015-12-11 21:15:04 +01:00
parent e175205e6e
commit b7f7c640c4
1 changed files with 34 additions and 40 deletions
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74
src/daemonizer/posix_fork.cpp
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@ -26,6 +26,39 @@ namespace {
void fork()
{
// Close the standard streams. This decouples the daemon from the terminal
// that started it.
close(0);
close(1);
close(2);
// We don't want the daemon to have any standard input.
if (open("/dev/null", O_RDONLY) < 0)
{
quit("Unable to open /dev/null");
}
// A process inherits its working directory from its parent. This could be
// on a mounted filesystem, which means that the running daemon would
// prevent this filesystem from being unmounted. Changing to the root
// directory avoids this problem.
if (chdir("/") < 0)
{
quit("Unable to change working directory to root");
}
// The file mode creation mask is also inherited from the parent process.
// We don't want to restrict the permissions on files created by the
// daemon, so the mask is cleared.
umask(0);
// Fork the process and have the parent exit. If the process was started
// from a shell, this returns control to the user. Forking a new process is
// also a prerequisite for the subsequent call to setsid().
@ -50,46 +83,7 @@ void fork()
// terminal.
setsid();
// A process inherits its working directory from its parent. This could be
// on a mounted filesystem, which means that the running daemon would
// prevent this filesystem from being unmounted. Changing to the root
// directory avoids this problem.
if (chdir("/") < 0)
{
quit("Unable to change working directory to root");
}
// The file mode creation mask is also inherited from the parent process.
// We don't want to restrict the permissions on files created by the
// daemon, so the mask is cleared.
umask(0);
// A second fork ensures the process cannot acquire a controlling terminal.
if (pid_t pid = ::fork())
{
if (pid > 0)
{
exit(0);
}
else
{
quit("Second fork failed");
}
}
// Close the standard streams. This decouples the daemon from the terminal
// that started it.
close(0);
close(1);
close(2);
// We don't want the daemon to have any standard input.
if (open("/dev/null", O_RDONLY) < 0)
{
quit("Unable to open /dev/null");
}
// Send standard output to a log file.
// Send standard output to a log file.
const char* output = "/tmp/bitmonero.daemon.stdout.stderr";
const int flags = O_WRONLY | O_CREAT | O_APPEND;
const mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;