Eu estava tentando atualizar de 16.04.1 a 16.04.3, atualmente o sistema é da versão 16.04.1
menghan@menghan:~$ uname -ra
Linux menghan 4.10.0-42-generic #46~16.04.1-Ubuntu SMP Mon Dec 4 15:57:59 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
Então, eu tentei o sudo apt-get update
No final, recebi
menghan@menghan:~$ sudo apt-get update
.........
.........
........
........
Reading package lists... Done
W: http://archive.canonical.com/dists/precise/Release.gpg: Signature by key 630239CC130E1A7FD81A27B140976EAF437D05B5 uses weak digest algorithm (SHA1)
W: The repository 'http://ppa.launchpad.net/bumblebee/stable/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: The repository 'http://ppa.launchpad.net/texlive-backports/ppa/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://ppa.launchpad.net/bumblebee/stable/ubuntu/dists/xenial/main/binary-amd64/Packages 404 Not Found
E: Failed to fetch http://ppa.launchpad.net/texlive-backports/ppa/ubuntu/dists/xenial/main/binary-amd64/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
Nesse sentido, nada é atualizado:
menghan@menghan:~$ sudo apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
bumblebee bumblebee-nvidia
0 to upgrade, 0 to newly install, 0 to remove and 2 not to upgrade.
Estou ciente de que tenho um laptop relativamente resistente para fazer o Ubuntu funcionar corretamente, pois ele tem bbswitch, nividia driver, bumbble-bee (da memória, uma dessas coisas estava quebrada quando eu estava tentando instalá-las, então eu tive que usar uma versão mais antiga) ....
Meu instinto é que uma dessas coisas não pode ser devidamente atualizada, fazendo com que nada seja atualizado no final ...