Changes
tyop
CPT is an extension to the OpenVZ kernel which can save the full state of a running VE and to restore it later on the same or on a different host in a way transparent to running applications and network connections. This technique has several applications, the most important being live (zero-downtime) migration of VEs and taking an instant snapshot of a running VE for later resume, i.e. CheckPoinTingCheckPointing.
Before CPT, it was only possible to migrate a VE through a shutdown and subsequent reboot. The procedure not only introduces quite a long downtime for network services, it is not transparent for clients using the VE, making migration impossible when clients run some tasks which are not tolerant to shutdowns.