Changing Owner / Changing Group in Linux

Changing Username and Group for a particular file

chown <username>:<groupname> <filename>

Changing Username and Group for directory and contents

chown -R <username>:<group> <directoryname>

Changing Username for a file

chown <username> <filename>

Changing Username for a directory

chown -R <username> <directoryname>

Changing Groupname for a file

chgrp <group> <filename>
chgrp -R <username> <directory>
chown :<group> <filename>
chown -R :<group> <directory>