nektos/act · error

conflicting options: cannot specify both --ip6 and…

Error message

conflicting options: cannot specify both --ip6 and per-network IPv6 address

What it means

Error [96]: ContainerStart failed — the Docker daemon refused to start the created job container. The wrapped daemon error identifies the cause: conflicting port bindings, bad network, missing image entrypoint, OCI runtime errors (exec format wrong for host arch), or host config the daemon rejects at start time.

Solutions

1. Read the wrapped message verbatim — it is the daemon's diagnosis (port/network/OCI)
2. Fix or remove conflicting options: create the network (docker network create foo) or drop the port binds
3. For cross-arch: docker run --privileged --rm tonistiigi/binfmt --install all then re-run act If SELinux denies: adjust label options or host policy

Example fix

# before: missing network
act --container-options "--network=my-net"
# after
$ docker network create my-net && act --container-options "--network=my-net"

// Pre-flight the options that break start
// network exists?
if _, err := cli.NetworkInspect(ctx, netName, client.NetworkInspectOptions{}); err != nil { log.Fatal("network missing") }
// host ports free?
for _, p := range usedHostPorts { if !portFree(p) { log.Fatalf("port %s in use", p) } }

if err != nil && strings.Contains(err.Error(), "failed to start container") {
	// wrapped daemon text after the colon is authoritative: port/network/OCI; fix that specific cause
}

When it happens

Trigger: ContainerStart erroring: port already allocated (host port conflicts), network specified in options doesn't exist, image entrypoint missing executable, binary architecture mismatch without emulation (exec format error), SELinux/AppArmor denial.

Common situations: --container-options '--network=foo' where foo was deleted; two act jobs binding the same host port; running arm64 images on x86 without qemu binfmt; enterprise hardening (SELinux) blocking container start.

Related errors

• --health-interval cannot be negative
• --health-timeout cannot be negative
• --userns: invalid USER mode
• --uts: invalid UTS mode
• bad format for path

AI-assisted analysis of nektos/act@4f41128141 (2026-08-15). Data as JSON: /api/errors/b3b53a81ba33f6d3. Report an issue: GitHub.

Appendix: source

Thrown at pkg/container/docker_cli.go:829

	if hasUserDefined && hasNonUserDefined {
		return nil, errors.New("conflicting options: cannot attach both user-defined and non-user-defined network-modes")
	}
	return endpoints, nil
}

func applyContainerOptions(n *opts.NetworkAttachmentOpts, copts *containerOptions) error { //nolint:gocyclo
	// TODO should we error if _any_ advanced option is used? (i.e. forbid to combine advanced notation with the "old" flags (`--network-alias`, `--link`, `--ip`, `--ip6`)?
	if len(n.Aliases) > 0 && copts.aliases.Len() > 0 {
		return errors.New("conflicting options: cannot specify both --network-alias and per-network alias")
	}
	if len(n.Links) > 0 && copts.links.Len() > 0 {
		return errors.New("conflicting options: cannot specify both --link and per-network links")
	}
	if n.IPv4Address.IsValid() && copts.ipv4Address != nil {
		return errors.New("conflicting options: cannot specify both --ip and per-network IPv4 address")
	}
	if n.IPv6Address.IsValid() && copts.ipv6Address != nil {
		return errors.New("conflicting options: cannot specify both --ip6 and per-network IPv6 address")
	}
	if n.MacAddress != "" && copts.macAddress != "" {
		return errors.New("conflicting options: cannot specify both --mac-address and per-network MAC address")
	}
	if len(n.LinkLocalIPs) > 0 && copts.linkLocalIPs.Len() > 0 {
		return errors.New("conflicting options: cannot specify both --link-local-ip and per-network link-local IP addresses")
	}
	if copts.aliases.Len() > 0 {
		n.Aliases = make([]string, copts.aliases.Len())
		copy(n.Aliases, copts.aliases.GetSlice())
	}
	// For a user-defined network, "--link" is an endpoint option, it creates an alias. But,
	// for the default bridge it defines a legacy-link.
	if container.NetworkMode(n.Target).IsUserDefined() && copts.links.Len() > 0 {
		n.Links = make([]string, copts.links.Len())
		copy(n.Links, copts.links.GetSlice())
	}
	if copts.ipv4Address != nil {

View on GitHub (pinned to 4f41128141)