You need to run "ulimit -c unlimited" with the user and at the session where you start the process. "ulimit" settings are inherited by processes started by that session, it's not like a system setting or something like that.
You must also make sure that the user that is running the process has write permissions to the current directory of the process, otherwise it won't be able to write the corefile.
If you give more information on which process is crashing and how it is started (/etc/init.d script?) we could help you more on where to put the "ulimit" settings for that process.
Filipe
the process is not a centos process. It is my program. I am logged in as root and I am running the process as root and I did run the "ulimit -c unlimited" as root.
I dont see the core file in the current directory, in /tmp or anyplace else? Very strange.
Jerry