O Ubuntu 17.04 é EOL: Fim da vida útil do Ubuntu
When an Ubuntu release reaches its “end of life” it receives no further maintenance updates, including critical security upgrades. We highly recommend that you upgrade to a recent version of Ubuntu at this point
Para continuar usando o Ubuntu 17.04, edite seu sources.list
da seguinte forma ( Gerador de lista de fontes do Ubuntu ):
sudo nano /etc/apt/sources.list
Depois das linhas:
###### Ubuntu Main Repos
deb http://us.archive.ubuntu.com/ubuntu/ zesty main restricted universe multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ zesty main restricted universe multiverse
###### Ubuntu Update Repos
deb http://us.archive.ubuntu.com/ubuntu/ zesty-security main restricted universe multiverse
deb http://us.archive.ubuntu.com/ubuntu/ zesty-updates main restricted universe multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ zesty-security main restricted universe multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ zesty-updates main restricted universe multiverse
Atualize seu sistema:
sudo apt update
sudo apt install openssh-server