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rpmrebuild is the fast way to create an customized rpm. This rpm can include modification in file like configuration file to will be used directly on the future or include some new files to improve the application.
To install rpmrebuild :
#yum install rpmrebuild
After modification of your application you can launch this command to create your rpm :
Others service is the possibility to modify the spec so you can add files, add commands on installation or others steps and more without recompile your application.