Setting Ownership and Permission: chown, chgrp, chmod

• chown root /path/to/file

• chgrp www-data /path/to/file

• chown root.www-data /path/to/file

• chmod 750 /path/to/file

• I'm root, and I still can't rm this file, wtf?

• Either you're messing with something you REALLY shouldn't, or you've been hacked – lsattr and chattr.