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

NAME
voliod - Start, stop, and report on Logical Storage Manager kernel daemons SYNOPSIS
/sbin/voliod /sbin/voliod [-f] set count OPTIONS
The following option is used by voliod: Force the kill of the last I/O daemon. Without this option, the I/O daemons can only be reduced to one. DESCRIPTION
The voliod utility starts, stops, or reports on Logical Storage Manager I/O daemons. An I/O daemon is a process that provides a process context for processing any work that needs to be done to process Logical Storage Manager I/O. When invoked with no arguments, voliod prints the current number of volume I/O daemons on the standard output. When invoked with the set keyword, the number of daemons specified by count will be created. If more volume I/O daemons exist than are specified by count, then the excess processes will be terminated. If more than the maximum number are created (currently 64), the requested number will be silently truncated to that maximum. The number of daemons to create for general I/O handling depends on system load and usage. One daemon for each CPU on the system is gener- ally adequate, unless volume recovery seems unusually slow. Each I/O daemon starts in the background and creates an asynchronously-running kernel thread and becomes a volume I/O daemon. The voliod utility does not wait for these threads to complete. NOTES
LSM automatically sets the number of I/O daemons when the system starts, so it is usually not necessary to set or change the number of I/O daemons with this command. LSM I/O daemons cannot be killed directly through the use of signals. The number of Logical Storage Manager I/O daemons currently running can only be determined by running voliod; I/O daemons do not appear in the list of processes produced by the ps(1) command. EXIT CODES
The voliod utility prints a diagnostic on the standard error, and exits if an error is encountered. If an I/O error occurs within a spawned I/O daemon thread, then the I/O is not reflected in the exit status for voliod. Otherwise, voliod returns a nonzero exit status on errors. Usage errors result in an exit status of 1 and a usage message. If the requested number of daemons cannot be created, then the exit status is 2, and the number of daemons that were successfully started is reported. If any other error occurs, the exit status is 3. FILES
The device used to report on and start volume I/O daemon kernel threads. SEE ALSO
fork(2), volintro(8), vold(8), voldctl(8) ,pthread(8) voliod(8)
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