How to solve the problem that Ubuntu 18.04 cannot start normally after switching from XEN to KVM

There are fewer and fewer businesses that still use the xen architecture. Some of those that used xen before have switched to the kvm architecture. Recently, a VPS was converted from xen to kvm. Unfortunately, I had installed ubuntu18.04 before, and found that I could not boot into the system normally after the conversion. I happened to have nothing to do and wanted to tinker with it, so I tried to find a solution myself. The main thing is to record it so that I can take it out and look at it next time I encounter it. Even if it is not exactly the same, it is good to learn from it. However, different businesses may use different system templates or related settings. It does not mean that the process in this article is applicable to all such problems.

Well, after the transfer, I was going to change the IP binding myself through the vnc console, but I found that the system did not start normally and entered the emergency mode. After entering the root password to log in, I ran the journalctl -xb command to check the system log. This section caught my attention, and it seemed to be a mounting problem.

I simply deleted the /dev/xvdb1 mount in /etc/fstab, and after deleting it, I rebooted the machine, and it finally entered the system normally. After logging into the system, I found that the same disk partition of kvm is now /dev/sdb1, which is different from the previous xen. After remounting and rebooting the test, I can enter the system normally.

However, after the machine directly modified the original network card configuration file IP, there was no network. Using the ip addr command to check, it turned out that the network card was eth0 when xen was used before, and the current network card is ens3. After changing the network card name and restarting the network, it was normal.