reference:
https://superuser.com/questions/645842/how-to-overwrite-a-symbolic-link-of-a-directory
The referenced article has made it very clear, I will add a little bit, citing the example of the original post
The proper way to do this is to use the -n, --no-dereference option like so.
$ ln -snf foo2 bar
This causes ln to treat the existing symlink as a file. Otherwise, it dereferences bar to foo1, descends into foo1 and uses the original TARGET name as the LINK_NAME and that's why you end up with a symlink to foo2 being created inside the foo1 directory. The manpage on ln states the following...
-n, --no-dereference
treat LINK_NAME as a normal file if it is a symbolic link to a
directory
Below is the shell output on my Arch Linux desktop with version 8.21 of ln with and without the --no-dereference option, I got the same results you did without the --no-dereference option, but using the --no-dereference option it worked as expected.
$ mkdir foo1 foo2
$ ln -s foo1 bar
$ ls -l bar
lrwxrwxrwx 1 drew users 4 Sep 17 12:51 bar -> foo1
$ ln -sf foo2 bar
$ ls -l bar
lrwxrwxrwx 1 drew users 4 Sep 17 12:51 bar -> foo1
$ ls -l foo1
total 0
lrwxrwxrwx 1 drew users 4 Sep 17 12:51 foo2 -> foo2
$ ln -snf foo2 bar
$ ls -l bar
lrwxrwxrwx 1 drew users 4 Sep 17 12:52 bar -> foo2To put it simply -n is to let the existing symbolic link (ie soft link) not be escaped and parsed, which is equivalent to outputting $ var as it is instead of taking the value it is assigned.
man ln shows four ways to create links
NAME
ln - make links between files
SYNOPSIS
ln [OPTION]... [-T] TARGET LINK_NAME (1st form)
ln [OPTION]... TARGET (2nd form)
ln [OPTION]... TARGET... DIRECTORY (3rd form)
ln [OPTION]... -t DIRECTORY TARGET... (4th form)
DESCRIPTION
In the 1st form, create a link to TARGET with the name LINK_NAME. In the 2nd
form, create a link to TARGET in the current directory. In the 3rd and 4th forms,
create links to each TARGET in DIRECTORY. Create hard links by default, symbolic
links with --symbolic. By default, each destination (name of new link) should not
already exist. When creating hard links, each TARGET must exist. Symbolic links
can hold arbitrary text; if later resolved, a relative link is interpreted in
relation to its parent directory.
Mandatory arguments to long options are mandatory for short options too.
If the soft link that happens to be overwritten points to a directory, without the -n parameter, it is equivalent to the second creation method, which is to create a soft link file in a directory.
