What command is typically used to copy a very large file quickly?

Using the 'rsync' command is often ideal for copying large files efficiently, especially over networked environments. It is designed to transfer files and directories while minimizing data transfer by only copying the differences between the source and target files. This capability makes it particularly useful for large files where a complete recopy would not only be time-consuming but also unnecessarily burdensome on resources.

Additionally, 'rsync' supports features like compression (which can significantly speed up the transfer of large files) and can resume interrupted transfers, making it more reliable for large file operations compared to other commands. It can also provide detailed progress information during the copy process, which is beneficial when dealing with extensive files.

The other options, while they serve useful purposes, do not match 'rsync' in this context for large file transfers. For example, 'cp' is a basic copy command that does not have the advanced features needed for efficiency with large files, particularly over the network. 'scp' is secure for copying files between systems but lacks the delta-transfer algorithm that makes 'rsync' faster in scenarios where files are partially transferred or updated. Meanwhile, 'tar' is primarily used for archiving multiple files into a single file; it isn't typically used for direct file transfers