Symbolic Links

UNIX filesystems have a feature called symbolic links, which are files that point to another file, called the target. They're similar to shortcuts in Windows.

There are two kinds of symbolic links: hard links and soft links.

Hard Links

Hard links create a file which points to the same space on the hard drive as the file which is being linked to, rather than to that file itself.

/home/me/file      /home/you/file
    |                    |
 hard link           hard link
    |                   ,'
    V               _.-`
HARD DRIVE <....--``

A file won't be deleted until every hard link to it is deleted.

To create a hard link, you use the ln command with the source file, and the target hard linked file:

ln arrayDat.txt arrayHard.txt

ls

Notice that any changes you make to arrayDat.txt will be reflected in arrayHard.txt.

Soft Links

Soft links create a file which points to the original file or directory.

/home/me/file <---Soft link--- /home/you/file
     |
     |
     V
HARD DRIVE

Soft links break if the original file is deleted.

To create a soft link, you use the ln command with the -s flag.

ln -s arrayDat.txt arraySoft.txt

ls -l

Notice that any changes you make to arrayDat.txt will be reflected in arraySoft.txt. The ls command will show that arraySoft.txt points to the file arrayDat.txt.

Your Luria home folder has a couple of soft links automatically set up pointing to storage servers so that common programs don't take up too much space on the head node.

Luria Cluster #Home Directory