I don't know how this happened

[danielsender]

I had a Centos 7 guest running under an Ubuntu 16.04 host. Everything was working well until today when I started the VM. The NetworkManager of the guest is not running and if I try starting the the NetworkManager as:

sudo service NetworkManager start

I get:

Redirecting to /bin/systemctl start NetworkManager.service
Failed to start NetworkManager.service: Unit is masked.

so I did:

sudo systemctl unmask NetworkManager.service

that appeared to be OK, but when I attempted to start the service again I got the same message.

I couldn't re-install NetworkManager because I'm without network. I would really appreciate any help.

Thanks.