Network interface name changed suddenly (ens18 -> enp6s18) - where to change back

Hi Folks,

I want to write down my findings to help anyone else searching for this topic.

I had a problem on my hypervisor an thus the univention-VM was not responsible any more. I invoked an clean reboot.

After the reboot the VM started to single-user mode (initramfs#) and mentioned me to do manual fsck so I did “fsck -y /dev/mapper/vg_ucs–root”. This repaired some stuff und so I rebooted.

Now the VM started to the normal console, but wasn’t reachable over the network. On the hypervisor display the IP of the Nextcloud container appeared instead of the external IP.

“ip addr show” displayed the nic ens18 down and so I took a look at /etc/network/interfaces. Instead of the nic ens18 there was enp6s18. I temporarily changed the name of the nic back to ens18 and restarted network “/etc/init.d/networking restart” and the system is reachable over the network again.

This ist not the final solution, because after the reboot there is enp6s18 again. But now the system is reachable and I can Access “Univention Configuration Registry”. I did a searching for “enp6”. Here I change “interfaces/primary” from enp6s18 to ens18.

This is not the end of the road, because there are some other UCR-Varibles with content “enp6s18”. Either I have to change these all (and maybe it is not working), or get the system back to recognise the nic as “ens18” as it did before.

I will work further to fix this issue and will tell back.



It because the predictable network interface names. Grrr, again. It hit me already sometimes in different places

The Problem is already known, like seen on: Kein Zugriff auf UCS Server nach upgrade auf 4.3

To repair the renamed network interface name, I did the following:

  1. Get Network running (its needed functionally for ucr commit)
  • nano /etc/network/interfaces
  • change enp6s18 to ens18
  • /etc/init.d/networking restart
  1. Change the name
  • nano /etc/univention/base.conf
  • you see interfaces/primary is ens18 or need to be set (The name, which the system names the nic at startup)
  • change all “enp6s18” to ens18 at “interfaces/enp6s18/” to “interfaces/ens18”
  1. Generate new Config files:
  • ucr commit

Like metioned in Step 1 the network has to be functional, because at ucr commit there is traffic to the ldap-server, etc. Your need to “be quick or be dead”, because the ucs system changes to the old/false config every few minutes.

Good luck,