@User: Putting a file on the command line is a quick way to load that one file. But any DEF file has references to other things, including components which may be in GDS or LEF format, and vias which would only be defined in the technology LEF file. So you should read, in order (1) the technology LEF file, (2) any LEF macro files, and finally (3) the DEF file. In your example, you will see the standard cells because the open_pdks installer creates .mag files for all the standard cells and then adds their location to magic's standard search path, where it will find them. But it will not find the technology LEF file or the standard cells unless you load them explicitly.