LibreCAD is an open-source, multi-platform, free 2D CAD software available for the most popular desktop platforms: Linux, Windows and Mac OS X. It is available in over 20 languages, has support for DWG files, it is capable of writing DXF files and has support for exporting SVG, JPG, PNG, PDF files, among others.
Also, it has layers, blocks, splines, polylines, ellipse tools, advanced tangent line & circle tools, transformation tools, an advanced snapping system and more. Because LibreCAD focuses on 2D geometry it is fast and lightweight, with an installer of less than 30mb.
The latest version available is LibreCAD 2.1.3, which has been released a while ago, coming with changes and new features.
Installation instructions:
The latest version of LibreCAD is available via the default repositories of Ubuntu 18.10 Cosmic Cuttlefish and Ubuntu 18.04 Bionic Beaver so installing it on your system should not be to difficult. All you need to do is update the local repository index and install the librecad package:
$ sudo apt update
$ sudo apt install librecad
If you want to test the unstable version of LibreCAD, you need to add the needed PPA to your system, update the local repo index and install the librecad package. Like this:
$ sudo add-apt-repository ppa:librecad-dev/librecad-daily
$ sudo apt update
$ sudo apt install librecad
Optional, to remove librecad, do:
$ sudo apt remove librecad