# test on DEBIAN 7 and php 5.4 Installing PHP-pear sudo apt-get install -y php-pear then dependencies sudo apt-get install -y build-essential php5-dev (other lib???) After I checkout latest version (Now It's 4.0.7 beta) Installing the apcu. sudo pecl install apcu Find extension directory sudo find / -name 'apcue.so' Create config file for php nano /etc/php5/mods-available/apcu.ini' Add these stuff in file (check path apcu.so): extension=/usr/lib/php5/20100525..../apcu.so #apc.enabled=1 #apc.shm_size=32M #apc.ttl=3600 #apc.user_ttl=7200 #apc.gc_ttl=3600 #apc.max_file_size=1M Create a symlink for load this: sudo ln -s /etc/php5/mods-available/apcu.ini /etc/php5/conf.d/20-apcu.ini The end restart the apache or there is any php-fpm you must restart this too Then (optionally) finish by cleaning buil tools: sudo apt-get remove --purge build-essential php5-dev --------- check: php -i | grep apc --------