Ubuntu has Lynis in its own repository, but it's fairly far behind what's current. If you're okay with using an older version, the command to install it is as follows:
sudo apt install lynis
If you want the newest version for Ubuntu or if you want to use Lynis on operating systems that don't have it in their repositories, you can
You can download Lynis from https://cisofy.com/downloads/lynis/.
The cool thing about this is that once you download it, you can use it on any Linux, Unix, or Unix-like operating system (this even includes macOS, which I've just confirmed by running it on my old Mac Pro that's running with macOS High Sierra.)
The cool thing about this is that once you download it, you can use it on any Linux, Unix, or Unix-like operating system (this even includes macOS, which I've just confirmed by running it on my old Mac Pro that's running with macOS High Sierra.)
Since the executable file is nothing but a common shell script, there's no need to perform an actual installation. All you need to do is extract the archive file, cd, into the resultant directory, and run Lynis from there:
tar xzvf lynis-2.7.5.tar.gz
cd lynis
sudo ./lynis -h
The lynis -h command shows you the help screen, along with all of the Lynis commands that you need to know about.