These are two commands to help us change the ownership of files, but we must be in the root or su mode first.
> chown <username> <file/folder> : used to change the owner of a file or folder
> chgrp <group> <file/folder> : used to change the group of a file or folder
> chown <username>.<group> <file/folder> : used to change the owner and the group in one step
> chown -R <username>.<group> <folder> : used to change the owner and the group of ALL files and directories under the parent <folder> (a very useful command !!)