This portal gives a list of resources for monitoring hardwares and softwares.
Logging and activity indicators
bootchart - Graphic generator detailing the boot sequence of the system.
bootlogd - Recording boot messages
auth.log - Authentification logs
Monitoring Network Connections
netstat - Monitor active connections on your system
iftop - Observe the flows on your network interfaces
tcpdump - Capture communications transmitted over your network interfaces
wireshark - Capture and analyze network traffic
apachetop - Realtime Apache monitoring tool
ngrep - grep for network traffic
Monitoring disk I / O
iotop - Observe the disk I / O
Monitoring the system load
procps - /proc file system utilities - a "pseudo" file system that provides information about processes. Contains free, kill, pkill, pgrep, pmap, ps, pwdx, skill, slabtop, snice, sysctl, tload, top, uptime, vmstat, w, watch
saidar - Watch the burden simply and concisely (with network and disks)
atop - Similar to saidar in the available information (also generates stats for long periods if run in the background via /etc/init.d/atop)
Watching a set of systems
These tools are typically used to monitor the overall functioning of a network computer fleet. In addition to your Debian servers, these tools can control most of the time heterogeneous systems. They are sometimes provided with plugins to monitor a particular feature of the system.
Pandora FMS - Open source monitoring system
collectd - a small daemon which collects system information periodically
monit - a utility for monitoring and managing daemons or similar programs