Azure 的自定义映像 VM 上没有 Internet

Question

I launched an Ubuntu 18.04 VM with Azure. I installed a bunch of stuff that I need. Then, I used the dashboard to create a custom image from this machine. After that, I checked that the image was okay by launching some machines with that image. Everything seemed to be working fine.

Today, I launched a new instance with my custom image. Then I tried to install a few things with apt-get install and I get the following error (eg for unzip):

sudo: unable to resolve host ABCDEFG: Resource temporarily unavailable
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package unzip is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'unzip' has no installation candidate

This same thing happens for any package I try to install. After testing some basic things with my repositories, I checked the internet connection with ping. Eg ping www.google.com which is also not working. I launched a vanilla Ubuntu 18.04 instance and I am not having these problems with that machine.

I have also tried sudo reboot but no luck with that. I did notice that when the system booted it shows the following error, also indicating that something is wrong with the internet:

Failed to connect to https://changelogs.ubuntu.com/meta-release-lts. Check your Internet connection or proxy settings

Any help is greatly appreciated.

Answer 1

So, after some digging around, I found this answer to something similar: https://askubuntu.com/questions/1045278/ubuntu-server-18-04-temporary-failure-in-name-resolution .

I used the following command and the internet started working again:

sudo ln -s ../run/systemd/resolve/stub-resolv.conf /etc/resolv.conf

This is a little different than the answer on askubuntu because this is on an Azure image. First, I noticed that my image was missing resolv.conf in /etc . Using ls -la /etc/resolv.conf on a different azure image, I saw that it was a symbolic link to ../run/systemd/resolve/stub-resolve.conf , so I created a link that matched this format on my machine and that fixed things.

** EDIT ** It's worth noting that when you deprovision the VM to create the custom image, it does say:

WARNING! The waagent service will be stopped.

WARNING! Cached DHCP leases will be deleted.

WARNING! root password will be disabled. You will not be able to login as root.

WARNING! /etc/resolv.conf will be deleted.

WARNING! xxxx account and entire home directory will be deleted.

Answer 2

When you create the custom image follow the step Deprovision the VM in the Azure VM, it will remove the file /etc/resolv.conf , so when you create a new Azure VM from the custom image, it cannot resolve the Domain name.

Hope this will help you to understand it.