Home / ubuntu / Questions / 1036266
In Process
kartik_subbarao
Asked: 2018-05-15 12:20:33 +0800 CST

What is the most authoritative file/process for managing IP addresses on an 18.04 server?

  • 772

The 18.04 server installation process creates /etc/cloud/cloud.cfg.d/50-curtin-networking.cfg, which, in turn, seems to generate /etc/netplan/50-cloud-init.yaml. I can't seem to find exactly how 50-cloud-init.yaml gets generated from 50-curtin-networking.cfg though.

What is the recommended way to manage IP addresses on an 18.04 server? Edit 50-curtin-networking.cfg, and then run some command (?) to update 50-cloud-init.yaml? Or some other process?

networking ip-address 18.04 netplan cloud-init

4 Answers

  1. Make your networking changes to the /etc/cloud/cloud.cfg.d/50-curtin-networking.cfg file as if you were putting them in the yaml file.

    Then do the following:

    sudo cloud-init clean
sudo cloud-init init
sudo netplan apply

    This will process your 50-curtin-networking.cfg file, generate the 50-cloud-init.yaml file and apply the yaml file netplan configuration.

    In this way, you can write your networking config in the 50-curtin-networking.cfg file as the comments imply you should do.

    A lot of the confusion between setting networking up in the 50-cloud-init.yaml file vs the 01-netcfg.yaml found in the /etc/netplan directory comes down to the installer used for Ubuntu 18.04 LTS.

    The live installer uses cloud-init, whereas the alternate installer does not.

    So for networking your installer choice changes how you will set up networking.

    ubuntu-18.04.1-server-amd64.iso -> 01-netcfg.yaml ubuntu-18.04.1-live-server-amd64.iso -> 50-curtin-networking.cfg

    • 4

  2. I assume this is an ordinary server, behind a router or switch that then connects to the internet. I'd rename the 50-cloud-init.yaml file:

    sudo mv /etc/netplan/50-cloud-init.yaml  /etc/netplan/01-netcfg.yaml

    Then find out the relevant interface name:

    ifconfig

    Assuming, for an example, that your relevant interface is enp0s25, edit the file:

    sudo nano /etc/netplan/01-netcfg.yaml

    Amend the file to read:

    network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s25:
      addresses: [192.168.100.40/22]
      gateway4: 192.168.100.1
      nameservers:
        addresses: [8.8.8.8,8.8.4.4]

    Of course, substitute your exact details here. Spacing, indentation, etc. are crucial. Proofread carefully. Save (Ctrl+O followed by Enter) and close (Ctrl+X) the text editor.

    Next:

    sudo netplan apply
sudo ip link set enp0s25 down
sudo ip link set enp0s25 up

    Did you get the requested IP address?

    ip addr show

    Can you ping?

    ping -c3 8.8.8.8
ping -c3 www.ubuntu.com

    If you get ping returns, you are all set.

    • 2

  3. I ended up editing the /etc/systemd/resolved.conf file and removed the comment on the DNS= line and added my preferred DNS entries with a space separating entries I.E.: DNS = 8.8.8.8 8.8.4.4

    • 0

  4. For me in Ubuntu 19.04 cloud-init init doesn't write 50-curtin-networking.cfg to 50-cloud-init.yaml unless you ask systemctl to restart the cloud-init-local service ...

    cloud-init clean
systemctl restart cloud-init-local.service
netplan apply
    • 0