Which command is used to create a hard link?

The command used to create a hard link in a Linux environment is "ln." This command allows users to create a link to a file that points directly to the inode of that file on disk, meaning both the original file and the hard link reference the same data. This setup enables any changes made to the file via one link to be reflected when accessing it through the other link, as they essentially point to the same physical file on the filesystem.

Other choices represent commands or functionalities that do not align with the creation of hard links in Linux. "link" is another command that could potentially create a hard link, but it is less commonly used and lacks the versatility that "ln" provides, such as its ability to create symbolic links with additional options. "hardlink" is not a standard command in Linux for creating hard links, and "mklink" is actually a command used in Windows to create symbolic and hard links, making it unsuitable for Linux environments. This context highlights why "ln" is the preferred and correct choice for creating hard links in Linux.