kicbase: fix deterministic machine-id breaking MAC addresses in multi-node Podman rootless clusters

[RobinMcCorkell]

Problem

/var/lib/dbus/machine-id is baked into the kicbase container image at build time. When the entrypoint's fix_machine_id runs systemd-machine-id-setup, it finds that file and derives /etc/machine-id from it — producing the same machine ID in every container.

This breaks anything that depends on the machine ID being unique per node. The most visible symptom is in multi-node minikube clusters using Podman rootless mode: a veth interface is placed into each Podman container, and systemd configures it according to MACAddressPolicy=persistent. That policy selects a MAC address based on the machine ID (via systemd-machine-id-setup, which reads from the D-Bus machine ID: https://www.freedesktop.org/software/systemd/man/latest/systemd-machine-id-setup.html). Because all containers share the same machine ID derived from the baked-in D-Bus ID, all nodes get identical MAC addresses on eth0, causing network failures.

Fix

Per https://systemd.io/CONTAINER_INTERFACE/, add a RUN step to the Dockerfile (before the final squash) that:

• Truncates /etc/machine-id to an empty file — the spec requires the file to be present but uninitialized so systemd can fill it on boot.
• Deletes /var/lib/dbus/machine-id — removes the baked-in D-Bus ID that was the source of the deterministic machine ID.

With these changes, systemd generates a fresh random machine ID on every container boot without any entrypoint assistance. This makes the existing fix_machine_id function in the entrypoint redundant — it has been removed.

Testing

Tested against the real kicbase image (gcr.io/k8s-minikube/kicbase-builds:v0.0.50-1772266598-22719) with Podman rootless.

Reproducing the bug

Both files contain the same baked-in value in the current image:

$ KICBASE=gcr.io/k8s-minikube/kicbase-builds:v0.0.50-1772266598-22719
$ podman run --rm --entrypoint bash $KICBASE -c '
    echo "/etc/machine-id:          $(cat /etc/machine-id)"
    echo "/var/lib/dbus/machine-id: $(cat /var/lib/dbus/machine-id)"
  '
/etc/machine-id:          636135c8833b3f1430bfc1ec69a2a4d1
/var/lib/dbus/machine-id: 636135c8833b3f1430bfc1ec69a2a4d1

Running systemd-machine-id-setup (as fix_machine_id does) produces the same ID every time:

$ for i in 1 2 3; do
    podman run --rm --entrypoint bash $KICBASE -c '
      rm -f /etc/machine-id; systemd-machine-id-setup 2>/dev/null; cat /etc/machine-id'
  done
636135c8833b3f1430bfc1ec69a2a4d1
636135c8833b3f1430bfc1ec69a2a4d1
636135c8833b3f1430bfc1ec69a2a4d1

Verifying the fix

Build a patched image applying the fix on top of the current kicbase:

$ podman build -t kicbase-patched - <<EOF
FROM $KICBASE
RUN truncate -s 0 /etc/machine-id && rm -f /var/lib/dbus/machine-id
EOF

Confirm the image state:

$ podman run --rm --entrypoint bash kicbase-patched -c '
    echo "/etc/machine-id size: $(wc -c < /etc/machine-id) bytes"
    ls /var/lib/dbus/machine-id 2>/dev/null || echo "/var/lib/dbus/machine-id: (removed)"
  '
/etc/machine-id size: 0 bytes
/var/lib/dbus/machine-id: (removed)

Each container now gets a unique machine ID:

$ for i in 1 2 3; do
    podman run --rm --entrypoint bash kicbase-patched -c '
      systemd-machine-id-setup 2>/dev/null; cat /etc/machine-id'
  done
4c971ecb6dc34159ad1da13a867a51c3
2d717cadb4804b1b9863f7b8b2da998d
b25726fead9246f691e97b3a63834de2

[k8s-ci-robot]

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This pull-request has been approved by: RobinMcCorkell
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[linux-foundation-easycla]

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[k8s-ci-robot]

Hi @RobinMcCorkell. Thanks for your PR.

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[minikube-bot]

Can one of the admins verify this patch?

[RobinMcCorkell]

The CLA signing page (and the support link) take me to a blank page on https://sso.linuxfoundation.org/login, looks like there's some CORS issues preventing the page from loading. I can't sign the CLA without that.

Also I don't think I can sign the CLA on behalf of Copilot 🙈