Execute o sudo apt-get update && sudo apt-get dist-upgrade
em um terminal
NOTA: "dist-upgrade" NÃO atualiza o sistema para uma nova versão do Ubuntu.
Veja man apt-get para detalhes
dist-upgrade
dist-upgrade in addition to performing the function of upgrade,
also intelligently handles changing dependencies with new versions
of packages; apt-get has a "smart" conflict resolution system, and
it will attempt to upgrade the most important packages at the
expense of less important ones if necessary. The dist-upgrade
command may therefore remove some packages. The
/etc/apt/sources.list file contains a list of locations from which
to retrieve desired package files. See also apt_preferences(5) for
a mechanism for overriding the general settings for individual
packages.