Quando vou para Configurações do sistema e clico em Fontes de software, nada acontece. Quando eu tento
sudo apt-get dist-upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Failed
The following packages have unmet dependencies:
gnome-shell : Depends: libcogl5 (>= 1.7.4) but it is not going to be installed
Depends: gnome-shell-common (= 3.2.2.1-0ubuntu0.1) but 3.4.0+git20120401.c16dbd76-0ubuntu1~11.10~ricotz0 is to be installed
gnome-shell-common : Breaks: gnome-tweak-tool (< 3.3) but 3.2.0-2ubuntu1~oneiric is to be installed
libmutter0 : Breaks: gnome-shell (< 3.3.92~) but 3.2.2.1-0ubuntu0.1 is to be installed
mutter-common : Breaks: gnome-shell (< 3.3.92~) but 3.2.2.1-0ubuntu0.1 is to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.
Responder1
Parece que o Gnome-shell trava a atualização. Você deve tentar desinstalar o pacote e reinstalá-lo quando a atualização for concluída (o gnome-shell está disponível no repositório em onírico).