symlink posts

PHP-FPM / Apache caching symlinks

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.

Moving folder symlink and trailing slash

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.