I am a relative newcomer to the world of Linux and have recently installed Ubuntu 18.04 in VMware on a win10 machine with BOINC 7.9.3. Initial installation went OK (after some hiccups with 32bit libraries) and have successfully run N144 models. Am now just over halfway through two N216 models but BOINC is no longer talking to the outside world. Neither is Mozilla!. As far as I know nothing changed on the setup appart from an unexpected computer shutdown - no work lost fortuntely. The problem is obviously that there is something odd about the network setup. VMware is using NAT and Win10 is talking quite happily to the outside world. I assume that Ubuntu should be using a VPN but I am not sure how to configure it - DHCP or manual. Can anyone offer me some advice please?

When logged in to Ubuntu terminal what is the output of:

sudo ip link
sudo ip addr
route

alan@ubuntu:~$ sudo ip link
[sudo] password for alan:
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: ens33: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ether 00:0c:29:32:08:85 brd ff:ff:ff:ff:ff:ff
alan@ubuntu:~$

alan@ubuntu:~$ sudo ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
link/ether 00:0c:29:32:08:85 brd ff:ff:ff:ff:ff:ff

alan@ubuntu:~$ route

Command 'route' not found, but can be installed with:

sudo apt install net-tools

alan@ubuntu:~$ sudo apt install net-tools
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed
net-tools
0 to upgrade, 1 to newly install, 0 to remove and 35 not to upgrade.
Need to get 194 kB of archives.
After this operation, 803 kB of additional disk space will be used.
Err:1 http://us.archive.ubuntu.com/ubuntu bionic/main amd64 net-tools amd64 1.60+git20161116.90da8a0-1ubuntu1
Could not resolve ‘us.archive.ubuntu.com’
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/n/net-tools/net-tools_1.60+git20161116.90da8a0-1ubuntu1_amd64.deb Could not resolve ‘us.archive.ubuntu.com’
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

Does this make sense?

Your virtual network adapter seems to have fallen down:

2: ens33: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ether 00:0c:29:32:08:85 brd ff:ff:ff:ff:ff:ff

Try:

sudo ip link set ens33 up && sudo dhclient ens33

That worked! Have just got 5 new N144 tasks!!! Thanks Lazlo. Have installed the net tools as well.

Your virtual network adapter seems to have fallen down:

Some network adaptors seem to drop out after a while on Ubuntu. Mine does on laptop. If I use a USB network adaptor I have it seems to stay up.

Some NIC chipsets have issues with Linux, ESXi, *BSD, and/or Windows. From my personal view it is 50% about the drivers used by the OS kernel and 50% about the driver model chosen for the virtual NIC when creating the VM. But I am just one data point.

I had that happen once on a laptop, I “cured” it by setting the power saving option off to prevent the os from disabling the network when not in use.