According to one embodiment, a computer machine includes a client virtual machine and a file server virtual machine configured to simultaneously run, a virtual machine manager configured to control booting of the client and file server virtual machines, a monitoring module configured to monitor whether a communication with an external file server is possible, an access control module configured to access to a duplicate file which is a duplicate of the file and is stored in a part of a local disk or a part of a memory which are managed by the monitoring module when the monitoring module determines that the communication is impossible after determining that the communication is possible, and a file deletion module configured to delete the duplicate file when the monitoring module detects the communication is impossible in a preset time.