I have used PRTG for quite some time to monitor my different virtual machines (locally and in the internet). While PRTG itself is super easy to install and administrate it is only working on top of windows. It is also limited to 100 sensors in the free version and is not open source.
I use a HP microserver Gen 10 to host my VMs which also could run windows but to run the resource-hungry OS for just the plain duty of monitoring my other machines in silence my RAM and Harddrivespace is too precious.
Overmore, as you might have noticed, I am a fan of free and open source software, so running windows was always bugging me.
Friends from the RaumzeitLabor in Mannheim introduced me to ZABBIX. Its easy to install on Linux, Nginx, PHP and MariaDB, very powerful and open source. Check out the website of zabbix to get installation instructions.
Use following codelines to install the Zabbix-Agent, the server connector, on the machines you want to monitor on Debian 10 / Buster:
wget https://repo.zabbix.com/zabbix/4.0/debian/pool/main/z/zabbix-release/zabbix-release_4.0-3+buster_all.deb dpkg -i zabbix-release_4.0-3+buster_all.deb apt-get update apt-get install zabbix-agent
After installing the agent make sure you fill in the IP-address of your Zabbix-Server:
For machines located outside of your firewall open Port 10050.
Finally enable and start the agent:
systemctl enable zabbix-agent systemctl start zabbix-agent