Quando você instalou o apache2, mod_ssl deve estar disponível em /usr/lib/apache2/modules/mod_ssl.so. Basta executar a2enmod ssl e, em seguida, service apache2 restart para ativá-lo.
Quando tento instalar o mod_ssl ele diz Não é possível localizar o pacote mod_ssl
$ sudo apt-get update Ign http://archive.ubuntu.com trusty InRelease Hit http://archive.ubuntu.com trusty-security InRelease Hit http://archive.ubuntu.com trusty-updates InRelease Hit http://archive.ubuntu.com trusty Release.gpg Hit http://archive.ubuntu.com trusty-security/main amd64 Packages Hit http://archive.ubuntu.com trusty-security/restricted amd64 Packages Hit http://archive.ubuntu.com trusty-security/universe amd64 Packages Hit http://archive.ubuntu.com trusty-security/multiverse amd64 Packages Hit http://archive.ubuntu.com trusty-security/main Translation-en Hit http://archive.ubuntu.com trusty-security/multiverse Translation-en Hit http://archive.ubuntu.com trusty-security/restricted Translation-en Hit http://archive.ubuntu.com trusty-security/universe Translation-en Hit http://archive.ubuntu.com trusty-updates/main amd64 Packages Hit http://archive.ubuntu.com trusty-updates/restricted amd64 Packages Hit http://archive.ubuntu.com trusty-updates/universe amd64 Packages Hit http://archive.ubuntu.com trusty-updates/multiverse amd64 Packages Hit http://archive.ubuntu.com trusty-updates/main Translation-en Hit http://archive.ubuntu.com trusty-updates/multiverse Translation-en Hit http://archive.ubuntu.com trusty-updates/restricted Translation-en Hit http://archive.ubuntu.com trusty-updates/universe Translation-en Hit http://archive.ubuntu.com trusty Release Hit http://archive.ubuntu.com trusty/main amd64 Packages Hit http://archive.ubuntu.com trusty/restricted amd64 Packages Hit http://archive.ubuntu.com trusty/universe amd64 Packages Hit http://archive.ubuntu.com trusty/multiverse amd64 Packages Hit http://archive.ubuntu.com trusty/main Translation-en Hit http://archive.ubuntu.com trusty/multiverse Translation-en Hit http://archive.ubuntu.com trusty/restricted Translation-en Hit http://archive.ubuntu.com trusty/universe Translation-en Ign http://archive.ubuntu.com trusty/main Translation-en_US Ign http://archive.ubuntu.com trusty/multiverse Translation-en_US Ign http://archive.ubuntu.com trusty/restricted Translation-en_US Ign http://archive.ubuntu.com trusty/universe Translation-en_US Reading package lists... Done $ sudo apt-get install mod_ssl Reading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package mod_ssl
Quando você instalou o apache2, mod_ssl deve estar disponível em /usr/lib/apache2/modules/mod_ssl.so. Basta executar a2enmod ssl e, em seguida, service apache2 restart para ativá-lo.