## 1 Introduction
The BT solution also has some extension protocols such as the Micro Transport Protocol (uTP) [20], a UDP-based protocol that implements a congestion-control algorithm in order to provide reliable data transportations while reducing congestion control issues and poor latencies that can be found in the typical BT over the TCP. Nowadays, P2P systems have widely been adopted in different areas, including file distribution [21; 22; 23; 24], audio and video streaming [25], voice over Internet protocol (VoIP) [26; 27], content distribution [28], and even digital cryptocurrencies [29; 30; 31]. The major advantages of the P2P protocol include their efficiency, reliability, and scalability. Thus, the P2P protocol can be used to fill the technology supply and demand gapin massive deployment via broadcast or multicast protocols. Many protocols are available for P2P file sharing, and the BT is one of the most popular file-sharing protocols with the highest adoption rate. However, when the BT protocol is used in bare-metal deployment, the problem stemming from insufficient temporary storage space to store the whole system image should be resolved. This temporary storage shortage issue happens because in bare-metal deployment, the whole local hard disk is the storage place where the OS and applications are to be deployed. Therefore, the hard disk cannot be used as a temporary storage space, as the local hard disk will be in the busy status when it is mounted to keep the image received from the sender. A single disk cannot be used for two purposes unless there are two or more disks in the computer. However, the availability of a second or more disks or partitions cannot be guaranteed. The random access memory (RAM) on the computer to be deployed is a possible candidate for serving as the temporary storage space. However, one cannot guarantee the availability of sufficiently large enough memory space to store the whole system image for both OS and applications. Open source or free software allows for the public availability of the software source code, thereby permitting modification. The copyright owner of open source or free software permits others to use, copy, modify, and distribute the source code [32; 33]. The open source or free software model empowers programmers to \"stand on the shoulders of giants\", so this model accelerates the use and improvement of existing software. Therefore, many high-quality programs have been developed and made available for the public. A lot of programs that use BT protocol to provide the P2P file-sharing ability are released under an open source, free software license. For example, BitTornado [34] was released under an Massachusetts Institute of Technology (MIT) license [35], while qBittorrent [36] was released under a General Public License (GPL) [33]. Although the BT protocol has been widely adopted in file sharing and many researchers have implemented the protocol for system deployment, to the best of the authors' knowledge, no BT-based deployment program in general can deploy OSs and applications absolutely without the availability of the temporary shortage issue. Hence, a novel efficient and reliable massive deployment system using the BT protocol that guarantees the system requiring no extra RAM or disk space is proposed. Furthermore, the system is backward compatible with older versions of mass deployment systems with the image format and procedure that the authors developed in the previous research [3]. The backward compatibility ensures interoperability with an older version of system deployment software. The backward compatibility support of the proposed BT-based mass deployment system is essential for existing users, because the novel system will not strand the users. Moreover, the diffusion and adoption of the novel system can be enhanced. When new features are added to an existing system, some functionalities might be removed or modified to prevent possible conflicts between the novel system and existing one(s). To support backward compatibility, some efforts are required.