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Full Discussion: when a process fails to write to /dev/log
Top Forums UNIX for Advanced & Expert Users when a process fails to write to /dev/log Post 302436540 by malcolmpdx on Monday 12th of July 2010 09:52:11 AM
Old 07-12-2010
Assuming you mean "when does a process fail to write to /dev/log?"

/dev/log is a semi-standard convention for syslog - syslog listens on this UNIX socket, and writes what is written there according to the rules in it's configuration file.

Given that, you've got three reasons why a process might not be able to log:
  1. The process in question isn't set up to do syslog. Using syslog is optional, and needs to be part of the process code.
  2. syslogd isn't running, so there's nothing reading from that socket.
  3. There is a syslogd running, and the process is set up to log to syslog, but it fails before it reaches the part of it's code when it does.

To check for the first, if you have the source code for the process, check it for calls to openlog(), syslog(), and closelog(), or if it's a shell script, check for calls to the logger program. Perl scripts will usually use Sys::Syslog or something similar.

To check for the second, do:
Code:
 $ ps -efawww | egrep syslog

or even better

Code:
 # lsof /dev/log

and see what has /dev/log open

To check for the third, well, you might try running the process under a debugger, and see if you can catch any writes to /dev/log or calls to syslog. Or, you could run the process via "strace" (truss on some Unixes) and look for writes that way.
 

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LEARN ABOUT REDHAT

tty

TTY(4)							     Linux Programmer's Manual							    TTY(4)

NAME

       tty - controlling terminal

DESCRIPTION

       The  file /dev/tty is a character file with major number 5 and minor number 0, usually of mode 0666 and owner.group root.tty.  It is a syn-
       onym for the controlling terminal of a process, if any.

       In addition to the ioctl() requests supported by the device that tty refers to, the following ioctl() request is supported:

       TIOCNOTTY
	      Detach the current process from its controlling terminal, and remove it from its current process group, without attaching  it  to  a
	      new  process  group  (that  is,  set  its  process group ID to zero).  This ioctl() call only works on file descriptors connected to
	      /dev/tty; this is used by daemon processes when they are invoked by a user at a terminal.  The process attempts to open /dev/tty; if
	      the open succeeds, it detaches itself from the terminal by using TIOCNOTTY, while if the open fails, it is obviously not attached to
	      a terminal and does not need to detach itself.

FILES

       /dev/tty

SEE ALSO

       mknod(1), chown(1), getty(1), termios(3), console(4), ttys(4)

Linux								    1992-01-21								    TTY(4)
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