After installation of new version of application such as a program that manages virtualization host is completed; virtual machine status information of a currently running first process of the application is imported to a second process of the application. The second process is initialized to establish a connection between the second process and a process of a machine emulator such as QEMU and the first process exits. Compared with the conventional techniques, since installation of the new version of the application has been completed after the new second process is initialized, the second process already runs based on the new version of software codes. Meanwhile, the virtual machine status information of the second process has been updated to conform to the first process before initiation, so that application-related functions are realized through the correct second process and thus interruption of the application-related functions is avoided during an upgrading process.