In the context of file transfers, what does the flag -D in RSYNC do?

The flag -D in RSYNC serves to preserve device files and special files when performing file transfers. This can be particularly important when backing up or mirroring entire file systems that contain device nodes or other special file types which are not simply regular files. By including the -D flag, RSYNC ensures that these critical system files are replicated accurately, maintaining the integrity and functionality of the system when restored.

Understanding the importance of preserving device files is essential for system administrators, especially when working in environments where hardware interactions are necessary. This is key in scenarios such as migrations or backups where the accurate reproduction of the original environment is required for proper system operations.