Argus (monitoring software)

Argus is a systems and network monitoring application. It is designed to monitor the status of network services, servers, and other network hardware. It will send alerts when it detects problems.
It is open-source software written entirely in Perl, and provides a web based interface.
Overview

Can monitor most network services.
Supports both IPv4 and IPv6
Includes graphing.
Web based front end.
Can monitor tens-of-thousands of services on common PC hardware.
Supports distributed and redundant configurations.
Configured using simple text files.

Details

Monitoring of network services (SMTP, POP3, HTTP, NNTP, ICMP, SNMP, FTP, Telnet, SSH, Gopher, NFS, DNS, Radius, IAX2, SIP, SunRPC, Whois, Rwhois, LPD, NTP)
Monitoring of server resources: CPU load, network load, and disk usage, using an agent.
Monitoring of the results of any command or script.
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