docker-in-docker feature not working on Ubuntu 26.04

[SrzStephen]

As indicated in #1235 this also appears to be broken on ubuntu 26.04 (New LTS release) due to the docker daemon being unable to start.

time="2026-05-02T09:11:20.106285682Z" level=info msg="Daemon shutdown complete" error="failed to start daemon: Error initializing network controller: error obtaining controller instance: failed to register \"bridge\" driver: failed to create NAT chain DOCKER: iptables failed: iptables --wait -t nat -N DOCKER: iptables v1.8.11 (legacy): can't initialize iptables table `nat': Table does not exist (do you need to insmod?)\nPerhaps iptables or your kernel needs to be upgraded.\n (exit status 3)"
failed to start daemon: Error initializing network controller: error obtaining controller instance: failed to register "bridge" driver: failed to create NAT chain DOCKER: iptables failed: iptables --wait -t nat -N DOCKER: iptables v1.8.11 (legacy): can't initialize iptables table `nat': Table does not exist (do you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.
 (exit status 3)

Testing

devcontainer features test --features docker-in-docker --filter docker_build --project-folder .

🔄 Testing 'docker-ps'

Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?


❌ docker-ps check failed.

🔄 Testing 'docker-build'

ERROR: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?


❌ docker-build check failed.