Wikipedia
LibreCAD
LibreCAD is a free Computer-aided design (CAD) application for 2D design. It works on Linux, OS X, Unix and Windows operating systems.
LibreCAD was developed as a fork of QCad Community Edition. The GUI of LibreCAD is based on Qt4 libraries, so it runs on several platforms in the same way.
Most of the interface and handle concepts are analogous to AutoCAD, making it easier to use for users with experience of this type of commercial CAD application.
LibreCAD uses the AutoCAD DXF file format internally for import and save files, as well as allowing export to many other file formats.