Umount: 0506-349 Cannot unmount /dev/hd10opt: The requested resource is busy

Check the process which are utilizing the filesystem which you are trying to 
unmount. 
try this out 
fuser -cux /abc 

This will give the list of process ids which are accessing this filesystem 
you can grep them and check for what its been used for 

Hope this helps...

In addition to fuser/lsof, check to make sure you don't have another filesystem mounted within /opt. Not long ago I spent a good amount of time battling with fuser trying to figure out what was causing that and it was simply another mounted filesystem that I had forgotten to unmount first. 

Caffeine helps during long overnights! 

-Dennis

Thanks to all....their is some system user like application team and root is using the /opt due to that I am unable to unmount the /opt. 

thanks 

Prakash

Check the inittab and the list of processes with the srcmaster as parent. The application that is keeping the fs busy is probably being re-spawned by one or the other.