conflicting options: cannot specify both --ip and per-networ

Error message

conflicting options: cannot specify both --ip and per-network IPv4 address

What it means

Error [95]: ContainerAttach (hijacked stream to the job container's stdout/stderr) failed in attach(). Act attaches after start to stream container output. Failure means the daemon refused the attach: container already exited, connection issue, or API incompatibility.

Source

Thrown at pkg/container/docker_cli.go:826

		}
		endpoints[n.Target] = ep
	}
	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())

View on GitHub (pinned to 4f41128141)

Solutions

docker logs <container> to see what the container printed before exiting; fix the entrypoint/workflow command
Ensure daemon is up and stable: docker info
Use a longer-running command/sleep in the container for debugging to confirm attach works
Update Docker Engine / act to matching versions

Example fix

# before: container command exits instantly, attach fails
jobs:
  a: {runs-on: ubuntu-latest, container: alpine, steps: [{run: sleep 0}]}
# after: keep it alive long enough or fix the real command
  steps: [{run: echo ok}]

Defensive patterns

Strategy: validation

Validate before calling

// Confirm container still running right before attach
if c, _ := cli.ContainerInspect(ctx, id); !c.State.Running {
	return fmt.Errorf("container exited early (code %d); see docker logs", c.State.ExitCode)
}

Try / catch

if err != nil && strings.Contains(err.Error(), "failed to attach to container") {
	logs, _ := cli.ContainerLogs(ctx, id, client.ContainerLogsOptions{ShowStderr: true})
	defer logs.Close() // read and surface why it exited
}

Prevention

Ensure job container commands don't exit instantly
Use stable local sockets for streaming
Match act and Docker Engine versions

When it happens

Trigger: cr.cli.ContainerAttach erroring: container exited before attach (fast-failing entrypoint), socket/tcp drop to daemon, or daemon too old for the attach options used.

Common situations: Job container whose command exits instantly; DOCKER_HOST remote with interrupted connections; Docker Desktop sleep/restart mid-run; attach racing container start on very short-lived containers.

Related errors

AI-assisted analysis of nektos/act@4f41128141 (2026-08-15). Data as JSON: /api/errors/db5ee0ff01caa122. Report an issue: GitHub.