Infrastructure & Engineering

Connecting Incus Instances to the Host Network: Successor to LXD

Otama
3 min read
Modified
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Table of Contents

This time, I introduce a method to connect an instance created with Incus directly to the Host side network, not the cluster internal network. I am using Netplan, but basic procedure is same even if not Netplan, so it should be applicable.

Preparation: Configure bridge network

First, configure a bridge network on the Host side.

Disable cloud-init

If using Ubuntu, a file called 50-cloud-init.yaml might interfere with network settings. Disable this. If not using Netplan, you can skip.

Terminal window
sudo touch /etc/cloud/cloud-init.disabled
sudo rm /etc/netplan/50-cloud-init.yaml

Write settings for bridge

Next, write config file for bridge network. Here I create a bridge network called br0 and use physical network device enp3s0 as its interface. Configure static IP address etc. on br0 side.

/etc/netplan/01-config.yaml
network:
  version: 2
  ethernets:
    enp3s0:
      dhcp4: false
      dhcp6: false
  bridges:
    br0:
      dhcp4: false
      dhcp6: false
      interfaces: [enp3s0]
      addresses: [192.168.100.101/24]
      routes:
        - to: default
          via: 192.168.100.1
      nameservers:
        addresses: [192.168.100.1]
      parameters:
        stp: false
        forward-delay: 0

Apply settings

Once done up to here, apply settings. After command execution, check if br0 network device is properly configured using ip a or ifconfig. It’s perfect if you also confirm that IP address is not assigned to physical device.

Note: If you mistake settings, remote connection might become impossible. I recommend working in an environment where you can connect a display to the physical machine just in case.

Terminal window
sudo chmod 600 /etc/netplan/01-config.yaml # If yaml wasn't made with root user
sudo netplan generate # Might be unnecessary
sudo netplan apply

Apply to servers in Cluster

If configuring Incus in cluster, creating br0 on servers other than Bootstrap Server is also necessary. Follow same steps on all servers in cluster. Adjust static IP addresses etc. appropriately.

Set Network to Profile

Finally Incus side settings. Inherit the bridge network (br0) created earlier and configure so Incus instance can connect to Host network. Since it seems impossible from network settings currently, write settings directly to Profile.

Pasting some reference threads.

Ref 1: https://discuss.linuxcontainers.org/t/incus-cluster-network-issue/18650 Ref 2: https://discuss.linuxcontainers.org/t/attaching-instances-from-the-managed-bridge-network-to-the-host-bridge-network/21530/3 Ref 3: https://discuss.linuxcontainers.org/t/how-to-use-my-local-lan-instead-of-incus-network-ipv4-and-ipv6/21564/4 Ref 4: https://discuss.linuxcontainers.org/t/incus-container-bridge-issues/22128/3

If setting via CLI

Profile is arbitrary, but applying to default profile here.

Terminal window
incus profile device remove default eth0
incus profile device add default eth0 nic nictype=bridged parent=br0 name=eth0

If setting via GUI

If using Incus GUI, you can move to YAML setting screen from following toggle in profile edit screen.

GUI Setting Screen
GUI Setting Screen

Change eth0 part as follows here.

Set Network to Profile 1
Set Network to Profile 1

Create Instance

Finally time to create an instance! Let’s create a new instance using the profile configured earlier.

Once instance starts, check if IP address is coming down properly with ip a etc. If acquired from the IP address range of host network you set, it’s almost success! While rejoicing, let’s try pinging too.

Supplement: Assign Static IP with Cloud-Init

As an example, if using Ubuntu 24.04 image, you can fix IPv4 address by describing Network Config in Cloud-Init settings as follows.

version: 2
ethernets:
  enp5s0:
    dhcp4: false
    dhcp6: true
    addresses:
      - 192.168.100.123/24 # Address you want to use
    routes:
      - to: default
        via: 192.168.0.1
    nameservers:
      addresses:
        - 192.168.0.1

Conclusion

This time I introduced the method to connect Incus instance to Host side network. It’s a useful setting when you want to join instance directly to host network separately from cluster network.

It required several steps like bridge network setting, disabling cloud-init, and changing Incus profile, but I’m glad it went well.

If it doesn’t work, comment and I’ll answer within my knowledge.

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