You are installing Virtualmin with the correct commands but you must install Virtualmin on a newly created server. The error with this particular install is being triggered due to an earlier failed attempt at installing Virtualmin on this server.
Ref - Warning: Virtual may already be installed…
You must re-instantiate the vps or reinstall the OS, then install Virtualmin. That should rid you of this problem.
I have created the server successfully but during configuring Virtualmin, I got this error when I clicked “Recheck and refresh configuration”.
Error Details:
(2)No such file or directory: AH02291: Cannot access directory ‘/var/log/virtualmin/’ for error log of vhost defined at /etc/apache2/sites-enabled/mailSMTP-02.growthandmotivation.com.conf:1
AH00014: Configuration check failed
Action ‘configtest’ failed.
The Apache error log may have more information.