Questions[virtualbox-networking](ubuntu)

I have Ubuntu 18.04 installed in a VirtualBox guest. The VM is configured with two adapters to provide internet access and connectivity to other VMs, which are:

Adapter 1: NAT (enp0s3)

Adapter 2: Internal Network (enp0s8)

When only the NAT adapter is enabled, internet access works fine.

When both adapters are enabled, I am still able to ping to the outside world by IP address, such as 8.8.8.8, but not by hostname, or web page, indicating a DNS issue.

enp0s3 is set to automatically receive an IP by DHCP and gets the usual 10.0.2.15 IP and is working fine when it is the only adapter enabled.

enp0s8 is set with a static IP (192.168.1.1), with the DNS and gateway options left blank. I am struggling to find the issue of why enabling the internal network adapter is causing this problem?

Host is Ubuntu 18.4, gnome 3.28.2.

Using Virtualbox 5.2.10_Ubuntu r121806, the guest is running PureOS release 8 and gnome 3.25.92. For this guest I am using a bridged adapter that allows VMs and is cable connected.

In the PureOS guest I enabled personal file sharing. I did NOT require a password. When I did that, it provided a message that to access the share I should use the URI dav://VBPOS.local. However, when I open Nautilus on the host, and in the field for "Connect to Server" I enter that URI, I get this error message: "Unable to access location / HTTP Error: Could not connect: Connection refused".

I spent hours searching online to figure this out, I didn't find anything that was helpful.

How do I fix this problem?

(tl;dr) My USB 3.0 ethernet adapter is found (lsusb), but the Ethernet interface is disabled after every reboot in Ubuntu 18.04 beta 2, even if I enable it with ip or ifconfig command (funny: it's found during installation and even connects, via dhcp, but is disabled after first reboot).

Long version: I am trying to get a DELOCK 62966 USB 3.0 > 4x Ethernet Adapter to work in a Ubuntu machine. Important: Ubuntu runs as VM in the latest Virtualbox, with a USB filter allowing access from the VM. It works well in a parallel running Windows VM. I also tried a different adapter (Lenovo Thinkpad USB 3.0 Ethernet adapter).

sudo lshw -C network gives the following result:

*-network DISABLED
description: Ethernet interface
physical id: 1
logical name: enx00e04c6801e1
[...]

I tried solutions from multiple forums from the past 10 years, e.g.:

sudo ip link set enx00e04c6801e1 up
sudo ip l s dev enx00e04c6801e1 up

This resulted in sudo lshw -C network not showing "DISABLED" anymore, but ifconfig shows that the interface does not have a valid IP. So I used sudo dhclient enx00e04c6801e1. Then, finally it showed a valid IP address.

Fyi, my /etc/network/interfaces was completely empty. I tried adding the following lines but they did not make any difference (I tried/rebooted multiple times)

auto lo
iface lo inet loopback
auto enx00e04c6801e1
iface enx00e04c6801e1 inet dhcp

Do I have to add all these steps in a script which starts at boot (if so how?) or is there a simple solution to tell ubuntu to use the adapter every time I boot?

Thank you for your help!!

UPDATE 1: Here's the result of cat /etc/netplan/*.yaml:

# This file is generated from information provided by
# the datasource.  Changes to it will not persist across an instance.
# To disable cloud-init's network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}
network:
    ethernets:
        enp0s3:
            addresses: []
            dhcp4: true
    version: 2

-> means I need to add the enx... as well?

I am using Virtual Box and if i lose internet connection or anything happens with my network adapter on host machine i will lose the internet connection on my Virtual Machine.

Even if i connect again, the host is fine but my Virtual Machine can't connect, i need to restart it in order to get internet.

Is there a way to restart networking on the Virtual Machine somehow without rebooting the whole Virtual Machine?

update:

i have tried this command:

sudo /etc/init.d/networking restart

but it just hangs and nothing happens.

How can i disable lxcbr0 from network? After ifconfig there exist a lxcbr0. I have checked list of lxc by enter lxc-ls and there was no lxc's. I remove lxc by apt-get remove. But still have lxcbr0.