Web server - 6. Symbolic Links, Limitation of Hard Links we
6. Symbolic Links, Limitation of Hard Links we first explain what symbolic links ( soft links, or even more often symlinks ) are. Symbolic links are files of a particular type whose sole content is an arbitrary string, which may or may not point to an existing file. When you mention a symbolic link on the command line or in a program, in fact, you access the file it points to, if it exists. For example: $ echo Hello >myfile $ ln -s myfile mylink $ ls -il total 4 169 -rw-rw-r–1 queen queen 6 Dec 10 21:30 myfile 416 lrwxrwxrwx 1 queen queen 6 Dec 10 21:30 mylink -> myfile $ cat myfile Hello $ cat mylink Hello You can see that the file type for mylink is l, for symbolic Link. The access rights for a symbolic link are not significant: they will always be rwxrwxrwx. You can also see that it is a different file from myfile, as its inode number is different. But it refers to it symbolically, therefore when you type cat mylink, you will in fact print the contents of the myfile file. To demonstrate that a symbolic link contains an arbitrary string, we can do the following: $ ln -s “I’m no existing file” anotherlink $ ls -il anotherlink 418 lrwxrwxrwx 1 queen queen 20 Dec 10 21:43 anotherlink -> I’m no existing file $ cat anotherlink cat: anotherlink: No such file or directory $ But symbolic links exist because they overcome several limitations encountered by normal ( hard ) links: You cannot create a link to an inode in a directory which is on a different file system to the said inode. The reason is simple: the link counter is stored in the inode itself, and inodes cannot be shared between file systems. Symlinks allow do this;