multi-named instance exist?

[Kevin Darcy]

If named is invoked successfully on startup, then the contents of the 
PID file will be overwritten with the new PID value.

If named *isn't* invoked successfully on startup, then that's a separate 
error condition that should be detected and dealt with, within the whole 
startup subsystem.

The problems with using "ps" to find the named process include:
-- you can get false matches if you don't tailor your string matching 
_just_right_,
-- unexpectedly "missed" matches if the command-line arguments change, 
even a little bit (e.g. if someone bypasses the wrapper script on an 
emergency basis to start the process manually, with the arguments given 
perhaps in a different order), and
-- since "ps" operates on a constantly-changing data source, it can 
"miss" legitimate processes in the process table. I've seen that happen 
many many times with "ps" on Solaris, not sure if Linux or other flavors 
of Unix have some sort of concurrency-control mechanism to prevent that 
phenomenon.

                                                                         
                                 - Kevin

dev_null at zoho.com wrote:
> I don't agree so much.
>
> some time when a system is reboot unnormally, named doesn't have the chance to remove its pid file.
> (when OS is shutdown normally, OS sends SIGTERM to named, named can exit and remove its own pid file.)
> after system is started, the pid number in name's pid file is maybe another process's.
> so kill -0 `cat named.pid` is successful, but named is not running at this time. 
> Am I right?
>
>
>  > Standard methodology would be to read the contents of the PID file and 
>  > see if that process is running (traditionally kill -0 $pid can be used 
>  > to non-intrusively check whether a given process is running). 
>  >  
>