instalação do laravel no ubuntu

Galera estou tentando instalar o laravel no ubuntu, mas estou tendo o seguinte problema

file_put_contents(/home/cintia/.composer/cache/repo/https---packagist.org/p-provider-2015-07.json): failed to open stream: Permission denied
http://packagist.org could not be fully loaded, package information was loaded from the local cache and may be out of date

Quem pode me ajudar?