[Techtalk] sighup, kill -9, sigkill, and all those related things

Kai MacTane kmactane at gothpunk.com
Fri Apr 14 06:54:41 EST 2006

At 12:56 PM 4/13/2006 , Kathryn Hogg wrote:

>Now the tricky part is that what each of those signals mean can be
>application development.  As you mentioned, a somewhat common convention
>is to reread config files upon receipt of a SIGHUP (kill -HUP $pid).  Of
>course you need to read that applications documentation to find out if
>thats what it does.

And sometimes even reading the docs isn't enough. I forget which daemon it 
was that I had to deal with on a regular basis, but there was one whose 
docs claimed that giving it a SIGHUP would cause it to re-read its 

In reality, giving it a SIGHUP caused the daemon to silently terminate 

This is why people looking over my shoulder as I perform system 
administration tasks are sometimes exasperated at my tendency to make sure 
that things actually worked. Start daemon, run 'ps auxwww' or pstree, HUP 
daemon, ps again... stop daemon, run it yet *again*, because some daemons 
take a while to shut down completely...

                                                 --Kai MacTane
"I am the storm. My voice is the river.
  Take from me, I fade into you..."
                                                 --The Last Dance,
                                                  "Fairytale (the Storm)"

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