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nerdctl rootless networking enables IPv6 in the RootlessKit namespace

Introduced 2026-09-20 · score 0.97

HOW TO USE IT

When testing IPv6 for a rootless container, set `CONTAINERD_ROOTLESS_ROOTLESSKIT_IPV6=true` and restart rootless containerd, then create an IPv6-capable CNI network with `nerdctl network create --ipv6 --subnet <v6-subnet> <network>`. IPv6 mainly affects outgoing connections with `slirp4netns` and `pasta`; `gvisor-tap-vsock` does not support IPv6, and the built-in port driver does not forward IPv6 ports.

Environment=CONTAINERD_ROOTLESS_ROOTLESSKIT_IPV6="true"
systemctl --user daemon-reload && systemctl --user restart containerd
nerdctl network create --ipv6 --subnet <v6-subnet> <network>

WHY THIS HELPS

Test a rootless container's IPv6 networking in a development environment.

BEFORE THIS CHANGE

Use the rootless network namespace without IPv6 enabled.

REQUIREMENTS AND LIMITATIONS

  • Version: v2.4.0
  • CONTAINERD_ROOTLESS_ROOTLESSKIT_IPV6: Boolean setting for IPv6 inside the RootlessKit network namespace; defaults to false. Set to true to enable.
  • --ipv6: Enables IPv6 on the network; use with a valid subnet.
  • --subnet <v6-subnet>: Specifies a subnet in CIDR format; use a valid IPv6 subnet for this task.
  • <network> (required): Network name positional argument for `nerdctl network create`.
  • Prerequisite: Rootless containerd must be set up; the docs direct users to `containerd-rootless-setuptool.sh install`.
  • Prerequisite: CNI plugins v1.1.0 or later are required to isolate the CNI bridge.
  • The setting defaults to false.
  • The setting mainly affects outgoing connections with `slirp4netns` and `pasta` network drivers.
  • It does not affect port forwarding in the built-in port driver.
  • The `gvisor-tap-vsock` network driver does not currently support IPv6.
  • The change covers `--port-driver=builtin` (the default); `--port-driver=slirp4netns` does not yet support IPv6 port forwarding upstream.

FIRST-PARTY EVIDENCE

Check the installed version and the source before using it. Entry JSON

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