Wednesday, August 26, 2009

Unix Create a Symbolic Link

SkyHi @ Wednesday, August 26, 2009
Q. How do I create links under UNIX / Linux operating systems?

A. You need to use ln command, which is a standard Unix / Linux / BSD command, used 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 Symboliclink Command

To create a symbolic link, enter
$ ln -s {/path/to/file-name} {link-name}
$ ln -s /shared/sales/data/file.txt
$ vi
$ ls -l
To delete a link, enter
$ rm {link-name}
$ rm
$ ls -l
$ ls -l /shared/sales/data/file.txt
If you delete the soft link itself ( , the data file would still be there ( /shared/sales/data/file.txt ). However, if you delete /shared/sales/data/file.txt, becomes a broken link and data is lost.
UNIX Create Hardlink Command

To create hard link, enter (without the -s option):
$ ln {file.txt} {hard-link}
$ ln /tmp/file link-here
You can delete hard link with 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.