By default ln makes hard links. A hard link to a file is indistinguishable from the original directory entry; any changes to a file are effective independent of the name used to reference the file. Hard links may not refer to directories (unless the proper incantations are supplied) and may not span file systems.
The -s option causes ln to create symbolic links. A symbolic link contains the name of the file to which it is linked. The referenced file is used when an open(2) operation is performed on the link. A stat(2) on a symbolic link will return the linked-to file; an lstat(2) must be done to obtain information about the link. The readlink(2) call may be used to read the contents of a symbolic link. Symbolic links may span file systems and may refer to directories.
Given one or two arguments, ln creates a link to an existing file sourcename. If targetname is given, the link has that name; targetname may also be a directory in which to place the link; otherwise it is placed in the current directory. If only the directory is specified, the link will be made to the last component of sourcename.
Given more than two arguments, ln makes links in targetdirectory to all the named source files. The links made will have the same name as the files being linked to.
The -r option causes ln to create remote links at the given location. Remote links are special files that identify places in Sprite where file system domains are attached to their parent domains. The source of a remote link must be an absolute path. In the normal case the source and target should be the same, ie. "ln -r /foo /foo".