Let’s imagine a simple scenario: you have just installed Debian 9 but you have forgotten to select a network options within VirtualBox. Most likely your linux system won’t be able to use a network because it didn’t set up default network setting due installation.
As a result you will be facing with with the similar error when trying execute
sudo apt-get update command
chip@chip:~$ sudo apt-get update [sudo] password for chip: Err http://ftp.us.debian.org jessie InRelease Err http://security.debian.org jessie/updates InRelease Err http://http.debian.net jessie-backports InRelease Err http://opensource.nextthing.co jessie InRelease Err http://security.debian.org jessie/updates Release.gpg Could not resolve 'security.debian.org' Err http://http.debian.net jessie-backports Release.gpg Could not resolve 'http.debian.net' Err http://opensource.nextthing.co jessie Release.gpg Could not resolve 'opensource.nextthing.co' Err http://ftp.us.debian.org jessie Release.gpg Could not resolve 'ftp.us.debian.org' Reading package lists... Done W: Failed to fetch http://ftp.us.debian.org/debian/dists/jessie/InRelease W: Failed to fetch http://security.debian.org/dists/jessie/updates/InRelease W: Failed to fetch http://http.debian.net/debian/dists/jessie-backports/InRelease W: Failed to fetch http://opensource.nextthing.co/chip/debian/repo/dists/jessie/InRelease
Don’t worry, it is not a trouble at all! It means that linux doesn’t know about your networks adapters yet. You just need to configure default network uses. To confirm this type
ping 220.127.116.11 and you should see some error message.
The steps you need to fix error will be these:
Turn on the NAT network adapter option inside the VirtualBox settings menu
ip addr and choose network interface which you want to activate. In my case it is
dhclient [your interface name] and default network will be changed.
To keep network setting activated when you has been restarting the system you need also add some config settings. Type
nano /etc/network/interfaces and add lines highlighted on the picture below: