Zabbix - Track, record, alert and visualize performance and availability of IT resources
htop - htop - an interactive process viewer for Unix. This is htop, an interactive process viewer for Unix systems. It is a text-mode application (for console or X terminals) and requires ncurses. Latest release: htop 2.
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
gtop - System monitoring dashboard for terminal
Prometheus - An open-source systems monitoring and alerting toolkit.
nmon - This systems administrator, tuner, benchmark tool gives you a huge amount of important performance...