• chmod 755 file Changes the permissions of file to be rwx for the owner, and rx forthe group and the world. (7 = rwx = 111 binary. 5 = r-x = 101 binary)
• chgrp user file Makes file belong to the group user.
• chown yourself/othersname file Makes yourself/othersname the owner of file.
• chown -R yourself/othersname dir Makes cliff the owner of dir and everything in its directory tree.

You must be the owner/suoder of the file/directory before changing the file permissions