Sentinel is a monitoring system which checks hosts and services you specify, notifying you when things go wrong and when they recover. It runs on multiple Linux distributions (including Fedora, Ubuntu, and openSuSE) as well as several Unix platforms (including Solaris and HP). The systems to be monitored can be nearly anything connected to a network. Some of the many features of Sentinel includes: Monitoring of network services (SMTP, POP3, HTTP, NNTP,PING, etc). Monitoring of host resources (CPU load, disk usage, etc). Simple plugin design that allows users to easily develop their own service checks. Parallel service checks. Ability to define network host hierarchy using ‘parent’ hosts, allowing detection of and distinction between hosts that are down and those that are unreachable. Contact notifications when service or host problems occur and get resolved (via email, pager, or a user-defined method), including detailed reporting of current and historical monitoring data. Ability to define event handlers to be run during service or host events for proactive problem resolution. Support for implementing redundant monitoring hosts. Optional classic web interface for viewing current network status, notification and problem history, log file, etc.