Symlink not updating as expected when using an absolute with relative path

Using -f with ln will overwrite any link that was already there, so as long as you have the correct permissions, it should work... It's always worked for me. What operating system are you using?

Ok, I found where my error is: one should not put the first / in path.

In other words, the commands in my questions should be:

Creation -> ln -s {path/to/file-name} {link-name}
Update -> ln -sfn {path/to/file-name} {link-name}

instead of

Creation -> ln -s {/path/to/file-name} {link-name}
Update -> ln -sfn {/path/to/file-name} {link-name}

considering my case.

First issue:

Quoting you:

Creations and deletions work fine. But updates do not work. After performing this command, the symlink becomes invalid.

The problem With the given directory structure:

~/scripts/test/ ~/scripts/test/remote_loc/ ~/scripts/test/remote_loc/site1/ ~/scripts/test/remote_loc/site1/stuff1.txt ~/scripts/test/remote_loc/site2/ ~/scripts/test/remote_loc/site2/stuff2.txt ~/scripts/test/remote_loc/site2/ ~/scripts/test/remote_loc/site3/stuff3.txt

and using the command:

ln -s /remote_loc/site1 test_link

Is that it creates a symbolic link in your $PWD, or present working directory, that points to a non-existing file off the /, or root, at /remote_loc/site1

If your PWD is in ~/scripts/ then you should have used this:

ln -s remote_loc/site1 test_link

else you could have used the full absolute path like:

ln -s /home/yourusername/remote_loc/site1 test_link

Second issue:

Quoting you:

I have read here and there that it is not possible to update/override a symlink. So there is contradictory information on the net. Who is right? If a symlink can be updated/overridden, how can I achieve this?

To answering your question "Who is right", I am not sure what exactly you read, or how it was understood. But, the following should help clear up:

1. What can be updated, and
2. What can not be updated without using appropriate switches.

Updating symbolic links with targets that are not directories.

ln -sf:
The -f or --force remove existing destination files, This is used to update a link's target or destination.

Example:

 ln -sf /tmp/test /tmp/test.link; ls -go /tmp |grep test
 -rw-r--r-- 1    0 Jun  8 17:19 test
 lrwxrwxrwx 1    9 Jun  8 17:27 test.link -> /tmp/test

But, as you can see, it will give the absolute path if absolute paths are in ln's arguments. Giving a full path is necessary when the present working directory is different than the link's parent directory.

Relative Paths:

ln -sfr:
The -r or --relative creates symbolic links relative to the link's location.

Example:

ln -sfr /tmp/test  /tmp/test.link  ; ls -go /tmp| grep test
-rw-r--r-- 1    0 Jun  8 17:19 test
lrwxrwxrwx 1    4 Jun  8 17:27 test.link -> test

But, updating a link to a directory will not work if the target is a directory.

Example:

ln -sf /tmp/testdir  /tmp/testdir.link  ; ls -go /tmp  |grep testdir
drwxr-xr-x 2 4096 Jun  8 17:48 testdir
lrwxrwxrwx 1    7 Jun  8 17:47 testdir.link -> testdir

As you can see, despite using absolute path names given in ln's argument above without the -r option, the symbolic link is still relative to the link.

Update Links to Directories:

ln -sfrn:
The -n or --no-dereference treats LINK_NAME as a normal file if it is a symbolic link to a directory.

Example:

ln -sfn /tmp/testdir /tmp/testdir.link; ls -go /tmp| grep testdir
drwxr-xr-x 2 4096 Jun  8 17:48 testdir
lrwxrwxrwx 1   12 Jun  8 17:48 testdir.link -> /tmp/testdir

As contrasted with:

ln -sfnr /tmp/testdir /tmp/testdir.link; ls -go /tmp| grep testdir
drwxr-xr-x 2 4096 Jun  8 17:48 testdir
lrwxrwxrwx 1    7 Jun  8 17:48 testdir.link -> testdir

$ touch test1 test2
$ ln -sf test2 test1
$ ls -l test[12]
lrwxrwxrwx 1 user01 user01 5 2012-05-17 14:41 test1 -> test2
-rw-r--r-- 1 user01 user01 0 2012-05-17 14:41 test2