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Top Forums Programming How to find if a process a daemon ? Post 302218737 by Perderabo on Saturday 26th of July 2008 08:15:11 AM
Old 07-26-2008
Quote:
Originally Posted by matrixmadhan
Any process guarded from SIGHUP signal as nohup process and detached from controlling terminal will have a ppid of 1
Not true. Any time any daemon which happens to be ignoring sighup forks, it creates a counterexample to this statement. (init could fork without creating a counterexample, but it never ignores hup)
Quote:
Originally Posted by matrixmadhan
but they are not daemonized.
Actually any process that happens to meet these criteria are daemons. No controlling terminal means the process is a daemon. Whether or not a process is a daemon has nothing to do with the ppid or what signals it is ignoring.

With most versions of unix when you log in on the system console, the ppid of your login shell will be 1. Before the rise of tcp/ip the ppid of every login shell was 1. None of these login shells are daemons, they all have controlling terminals. You still may have other getty lines in /etc/inittab. Each such line is a potential interactive shell with a ppid of 1. But most other children spawned by init do not open ttys and remain daemons.

When a process exits, its children become owned by init. This does not impact whether of not those children are daemons. Some are. Some aren't.

cron will not have a pid of 1. Every time cron spawns a process, that new process is a daemon. Each of these daemons will not have a ppid of 1... their ppid will be pointing to cron.

When you need to determine if a process is a daemon or not, the ppid is completely irrelevant. Daemons and non-daemons can have a ppid of 1. Daemons and non-daemons can have a ppid other than one.

Daemons sometimes choose to not ignore sighup. Both inetd and init itself are examples of daemons that are listening for a HUP. When they get one, they reconfigure themselves. But it is more common for a daemon to be ignoring HUP.

It really it very simple.
Daemons have no controlling terminal.
Non-daemons have a controlling terminal.

Examples of stuff that have no bearing on a process' daemon status...
pid
ppid
signal mask
 

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HALD(8) 						      System Manager's Manual							   HALD(8)

NAME
hald - HAL daemon SYNOPSIS
hald [options] DESCRIPTION
hald is a daemon that maintains a database of the devices connected to the system system in real-time. The daemon connects to the D-Bus system message bus to provide an API that applications can use to discover, monitor and invoke operations on devices. For more information about both the big picture and specific API details, refer to the HAL spec which can be found in /usr/share/doc/packages/hal/spec/hal- spec.html depending on the distribution. OPTIONS
The following options are supported: --daemon=yes|no Specify whether to run in the foreground or the background. --verbose=yes|no Enable verbose debug output. --use-syslog Enable logging of debug output to the syslog instead of stderr. Use this option only together with --verbose. --help Print out usage. --version Print the version of the daemon and exit. BUGS AND DEBUGGING
Please send bug reports to either the distribution or the HAL mailing list, see http://lists.freedesktop.org/mailman/listinfo/hal on how to subscribe. First, to obtain useful debug traces you will need to have debuginfo packages installed. On a Fedora system this is in the hal-debuginfo package and can be installed via the yum update program. Second, shut down the existing hald daemon instance; on a Fedora system this is achieved by /etc/init.d/haldaemon stop After having shut down the daemon, you might want to run pkill hald to ensure that all the helper processe of hald are killed too. To start the HAL daemon, use /usr/sbin/hald --daemon=no --verbose=yes If the daemon crashes, you can start it under a debugger via gdb /usr/sbin/hald and then typing run --daemon=no --verbose=yes at the (gdb) prompt. To capture a back trace, use the bt command and attach this to the bug report. Please also attach the output of lshal(1) in the bug report if possible (it's not possible if the hald daemon crashed). If the nature of the bug has to do with hotplugging, attach two outputs of lshal(1) - one before the device hotplug event and one after. SEE ALSO
udev(7), dbus-daemon(1), lshal(1), hal-set-property(1), hal-get-property(1), hal-find-by-property(1), hal-find-by-capability(1), hal-is- caller-locked-out(1) AUTHOR
Written by David Zeuthen <david@fubar.dk> with a lot of help from many others. HALD(8)
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