Vzwatchd is an OpenVZ monitoring daemon that informs the server administrator by email when a limit of the container is reached. OpenVZ is a Linux Kernel virtualisation technology that is often used by Web Hosting services, it is the free core of the commercial virtuozzo virtualisation application. OpenVZ is a lightweight virtualisation which has less overhead then KVM or XEN, it is more like a Linux LXC jail but with advanced limit options to define how many ressources a virtual machine may use and it has support for filesystem quota.
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