Static IP for VM

Without any settings, Multipass's VM will be reallocated with a new IP address when VM is restarted or the host computer is rebooted. This may result in host kubectl being unable to access its VM environment. Also if you have configured multi-node cluster, the connection between the nodes might be disconnected due to a change in the IP address.

If you do not configure a static IP, you may need to change or re-configure the settings on each VM restart. If you're unable to maintain VM online all the time, it's better to assign a static IP.

Multipass provides an official guide related to static IP.
To simply explain this process:

1. Create a switch or bridge for static IP.
   Because the method varies depending on the OS, so we'll not discuss about it.

2. Connect the created switch/bridge to the VM, and run it.

   info

   In Windows, it is difficult to find information related to step 1~2, but there is a some nice post about it including this link, so I think you can refer to it.

3. Connect to the Multipass VM Shell.
   You can check the newly created MAC address by ip a command.
   In the following case, it was created under eth1.

   

4. Type the following command.

   sudo vi /etc/netplan/50-cloud-init.yaml

   Or you can create a new yaml file in the /etc/netplan folder as well.
   Please refer to the Multipass guide to write it down.
   For here we'll modify the existing file.

   /etc/netplan/50-cloud-init.yaml

   # This file is generated from information provided by the datasource.  Changes
   # to it will not persist across an instance reboot.  To disable cloud-init's
   # network configuration capabilities, write a file
   # /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
   # network: {config: disabled}
   network:
     ethernets:
       eth0:
         dhcp4: true
         match:
           macaddress: 52:54:00:18:36:d5
         set-name: eth0
       eth1:
         dhcp4: no
         match:
           macaddress: "00:15:5d:db:11:09"
         addresses: [192.168.0.4/24]
     version: 2

5. Apply the settings with the following command in the host.

   multipass exec -n <vm-name> -- sudo netplan apply

6. Afterwards, use commands such as ping to test the IP address.

7. Repeat steps 2 through 6 for extra VM.

C:\Users\HU>multipass list
Name                    State             IPv4             Image
k3s-master              Running           172.29.147.34    Ubuntu 22.04 LTS
                                          192.168.0.2
k3s-worker-1            Running           172.29.146.255   Ubuntu 22.04 LTS
                                          192.168.0.4
k3s-worker-2            Running           172.29.154.49    Ubuntu 22.04 LTS
                                          192.168.0.8

The configured static IP does not change even if you restart the VM.

caution

In the multi-node cluster, to communicate between nodes using a static IP, all nodes must be configured with static IP with same bridge/switch.

info

After static IP is set, certificate error can be occured when you try to control the VM's K8S on host.

couldn't get current server API group list: Get "https://<your-ip>:6443/api?timeout=32s":
tls: failed to verify certificate: x509: certificate is valid for ..., not <your-ip>

In this case, reinstall K3S by using following command.¹

curl -sfL https://get.k3s.io | INSTALL_K3S_EXEC="--tls-san <your-ip>" sh -s -

Footnotes

1. https://github.com/k3s-io/k3s/issues/1381 ↩