GNU Krell Monitors (GKrellM) is a computer program based on the GTK+ toolkit that creates a single process stack of system monitors. It can be used to monitor the status of CPUs, main memory, hard disks, network interfaces, local and remote mailboxes, and many other things. Plugins are available for a multitude of tasks, for example, controlling the XMMS media player or a SETI@home client from within the stacked monitor. GKrellM is popular among users of Linux and other Unix-like operating systems.