You need to use the ln command. It is a standard Unix / Linux / BSD command to create links to files. There are two types of links under UNIX, hard and soft link:
Hard link vs. Soft link in Linux or UNIX
[a] Hard links cannot links directories ( cannot link /tmp with /home/you/tmp)[b] Hard links cannot cross file system boundaries ( cannot link /tmp mounted on/tmp to 2nd hard disk mounted on /harddisk2)
[c] Symbolic links refer to a symbolic path indicating the abstract location of another file
[d] Hard links, refer to the specific location of physical data.
UNIX create a symbolic link command
To create a symbolic link, enter:$ ln -s {/path/to/file-name} {link-name}
$ ln -s /shared/sales/data/file.txt sales.data.txt
$ vi sales.data.txt
$ ls -l sales.data.txt
How do I delete a symbolic link?
To delete a link, enter:$ rm {link-name}
$ rm sales.data.txt
$ ls -l
$ ls -l /shared/sales/data/file.txt
If you delete the soft link itself (sales.data.txt) , the data file would still be there ( /shared/sales/data/file.txt ). However, if you delete /shared/sales/data/file.txt, sales.data.txt becomes a broken link and data is lost.
UNIX create a hardlink command
To create hard link, enter (without the -s option):$ ln {file.txt} {hard-link}
$ ln /tmp/file link-here
How do I delete a hard link?
You can delete hard link with the rm command itself:$ rm {hard-link}
$ rm link-here
If you delete a hard link, your data would be there. If you delete /tmp/file your data still be accessible via link-here hard link file.
Source : http://www.cyberciti.biz/faq/unix-creating-symbolic-link-ln-command/