TYPO3 Core

Install Tool -> Important Actions -> Core Update

After downloading and extracting a new TYPO3 core package, the symlink is updated automatically, pointing to the new source directory.
For example (an update from 6.2.2 to 6.2.3):

lrwxrwxrwx typo3_src -> /home/ernie/www/htdocs/typo3_src-6.2.3
drwxr-sr-x typo3_src-6.2.2
drwxr-sr-x typo3_src-6.2.3

Using an absolute path to the target directory (here: /home/ernie/www/htdocs/typo3_src-6.2.3) makes it hard(er) to move instances around, e.g. from user "ernie" to user "bert" :-) Typically, you only need to move/copy directory "www" from /home/ernie/ to /home/bert/ (plus the adjustment of permissions), but in this case, this would not work.

Another example could be a change of the path, e.g. from /home/ernie/www/htdocs/ to /home/ernie/public_html/.

A more robust and admin-friendly solution would be to check (before the core update), if the symlink points to a relative directory and in this case, retain this option, rather than changing to an absolute path.

lrwxrwxrwx typo3_src -> typo3_src-6.2.3
drwxr-sr-x typo3_src-6.2.2
drwxr-sr-x typo3_src-6.2.3