Nixos-anywhere deployed server becomes unreachable after setup

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1

Hi everyone!

Using nixos-anywhere, i deployed Nixos to Ubuntu and Debian VPS’ hosted by contabo, seemingly successful. But after the server reboot, the system is completely unreachable (ssh times out, ping gets lost).
I followed nixos-anywhere’s quick-start guide without any major modifications. The setup runs without any errors and finally echoes “### Done! ###”

How do i even start to debug this?

output of:

nix run github:nix-community/nixos-anywhere -- \
      --generate-hardware-config nixos-generate-config ./hardware-configuration.nix \
      --flake ./#generic \
      --target-host root@212.90.120.119 \
      --debug \
      2>&1 > output.txt

Is here

Maybe related: i can access the vm’s terminal via vnc and it shows the login shell, but it won’t accept the root password (i temporarily tried very simple ones to rule out misstypes)

2

If i set a password with users.users.root.hashedPassword i can at least login via a VNC-viewer.
ip addr then shows, that the ip has changed, which would explain why icmp and ssh goes nowhere.

3

Do you have an ssh key set up in your configuration.nix ?

4

yes.
Contabo also uses netplan to configure the interfaces, which means i have a handy .yaml file as a template to define interface addr. and routes in my nix config.

bit of a headache, but let’s see if this works.

5

I think I forgot to read the log you posted, so you have your public ssh key set up.
I can only say that I use a vaguely similar deployment on hetzner and for logging on to the deployed vm I use a match block (HostName is the ip of the vm obviously) in my ssh_config whatsoever and ssh thefinevm to log onto it:

Host thefinevm
  User root
  HostName ip.ip.ip.ip
  IdentityFile ~/.ssh/id_ed25519
  IdentitiesOnly yes
  PubKeyAuthentication yes
  PasswordAuthentication no
  UserKnownHostsFile /dev/null
  StrictHostKeyChecking no
  LogLevel FATAL

It’s a fairly fresh vm and certainly has room for improvements but as a template it should do, other means of logging in can be explored when that is working.

6

ssh isn’t the problem here, when i can’t even ping the server!
As i mentioned in my second post, the servers ip has changed after nixos was installed. As a result the server isn’t reachable under it’s assigned (static) IP.

7

Try networking.useDHCP = false; ?

8

DHCP respects staticly set network configurations, Disabling it would mean i wouldn’t even get assigned a dynamic IP.
I’ve tested it and as expected the ethernet interface is down as a result.

as i’ve said, i have to carry over the static network configuration (originally handled by netplan on debian) and leave dhcp enabled, because dhcpd was also running on the host-provided images.

9

Someone wrote down what they did here: NixOS on Contabo (via)

1 Like
10

ah cool! thats exactly what i’m doing now.

i’ll post the gist, when i get it working

1 Like
11

here’s the gist of a working config. Nixos Networking on a contabo VPS · GitHub