do create an entry I just touch a file, say, 192.168.0, to the appropriate directory AND chown this file to be consistent with the others that are already in place.
should I do it? this file will be forgotten by a greylist cleanup?
or should I simply create it with root permissions to not permit deletion?
To add an entry into the whilelist, I copy an existing file already there to the new file name then chown with permissions like the other files located in whilelist. The greylist cleanup will ignore these files. They will be there until you remove them.