At Cogneato, we use symlinks to point the web server to different versions of our software for websites. Sometimes, especially on our Ubuntu server, which uses PHP-FPM to serve PHP files through Apache, I was noticing problems caused by scripts being loaded from the previous symlink destination when I changed to the new one. There seems to be some sort of caching going on. The solution was to restart PHP-FPM and Apache after switching the symlinks. On Ubuntu, this looks like:
ln -s /path/to/new-version /path/to/software-link \
&& sudo service php7.2-fpm restart \
&& sudo service apache2 graceful
where the 7.2 is the version of PHP being used. Haven’t noticed the problem since.
It caught me by surprise that if you use mv on a symlink to a folder and have a trailing slash on the path, it will move the entire original folder rather than the symlink. As a simple example, if you have a symlink ‘symlink’ pointing to the folder ‘original’ and run mv symlink/ new-symlink, you will end up with ‘original’ now being named ‘new-symlink’ and a symlink ‘symlink’ still pointing to the now non-existant ‘original’. Luckily, merely reversing the arguments will move the folder back to its original location: mv new-symlink symlink/. The symlink becomes like a magic portal. I probably wouldn’t have run into this if it weren’t for the ‘fish’ shell adding trailing slashes when doing tab completions on folder paths or symlinks to them.