RANCID (Really Awesome New Cisco confIg Differ) collects a router's (or device's) configuration, including software and hardware (cards, serial numbers, etc.), and uses CVS to display differences from a previous collection. It supports Cisco routers, Juniper routers, Catalyst switches, Foundry switches, Redback NASs, and ADC EZT3 muxes. The Beta version currently includes support for Bay Networks (nortel) routers and Extreme switches. Rancid also includes a lookingglass and the device login scripts may be used to automate a number of tasks.
F-Watch is a kernel module that reports changes on files to /dev/fwatch. It hooks into the sys_calls and does not require a kernel patch. To activate watching for certain events, users need to run ioctl to register the wanted events; examples are in the src dir. Ioctl can be used during runtime to individually change the required events.