Linux links with "ln" command [closed]

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I'm writing a shell script in bash where I'm making some links between files, but I'm not sure what kind of link to use (physical or symbolic). Doing some research, I've noticed that it's more common to use symbolic links instead of physical ones. My question is why to use symbolic links when they require an indirection (it creates an extra I-node to safe the information about the real I-node of the file) instead of using hard links that point directly to the file?

In other words:

Why

ln -s ...

instead of

ln -P ...

Answer 1

The main reason for symlinks is that a 'soft' symlink can cross filesystem boundaries. The file representing the symlink will contain a string that is the actual path of the file being pointed at. As long as the end-user representations of that path remain the same, the symlink will work. If you move the file at the end of the symlink, the symlink will now be stale (aka "dangling"), because the resource it pointed at no longer exists.

A hard (aka physical) symlink works at the inode layer. Since inodes are only unique within a single file system, you cannot hardlink ACROSS file systems. You could quite easily run into a duplicate inode situation if this were allowed. The benefit is that no matter where you move the target of a hardlink, the links pointing at the resource will "follow", because they're pointing at the inode itself, and don't care what the actual path/resource name is.

Answer 2

Off the top of my head:

1. symbol links work across filesystems. If you don't want to keep track of what filesystem the source file and destination link are on, or if you sometimes move files across filesystems, it is less of a hassle to use symbolic links.

2. $@&#$& emacs backup files. When you edit, say file.txt and make a change to it in emacs, emacs renames the original file to file.txt~ and saves your changes under the original file name. If there was a hard link to file.txt, it is now linked to file.txt~, which is probably not what you want. A symbolic link to file.txt will still point to the updated inode.

Answer 3

A hardlink can only work on the same filesystem, renames the inode. A file can only be deleted when the last link to its inode is gone. Hardlinks usually are for files instead of directories.

A symlink is an actual file containing a path to another file. Symlinks can work across file systems as well. They can point to different file types as well. A symlink can also point to either files or directories.

Answer 4

• Hard links don't make sense across filesystems, since they're basically pointers to inodes on the local FS. Symlinks don't care; since they're just names, they can live anywhere.

• If you look at the directory listing and see a symlink, you know it's to a particular other location. Hard links, on the other hand, offer no such clue. You might not know you were playing around in some important file til you stat both its names.