docker/cli · error · invalidParameterErr

conflicting options: cannot specify both --link and…

Error message

conflicting options: cannot specify both --link and per-network links

What it means

Returned by applyContainerOptions when both the global --link flag (copts.links) and per-network links inside the advanced --network notation (n.Links) are specified for the first network (opts.go:815-817). Links are endpoint-scoped on user-defined networks, so specifying both sources is ambiguous and rejected as invalidParameter.

Solutions

Use only the advanced per-network link: --network=mynet:link=cache.
Or use only the global --link=cache and drop the link= from the --network value.
Modernize away from --link entirely using user-defined DNS where possible.

Example fix

// before
docker run --link=redis --network=mynet:link=cache myimage
// after
docker run --network=mynet:link=cache myimage

Defensive patterns

Strategy: validation

Validate before calling

if len(n.Links) > 0 && copts.links.Len() > 0 {
    return errors.New("cannot specify both --link and per-network links")
}

Prevention

Pick one link notation; prefer per-network link= in advanced form.
Where possible, replace --link with user-defined network DNS.
Audit migrated compose files for residual global --link flags.

When it happens

Trigger: Running `docker run --link=redis --network=mynet:link=cache ...` where the --network value carries a `link=` option and the global --link is also present. Applies to the first network only (i==0).

Common situations: Migrating legacy --link usage into advanced --network notation without removing the old flags; compose templates that emit both link forms; assuming both are additive.

Related errors

AI-assisted analysis of docker/cli@4f84911bfe (2026-08-07). Data as JSON: /api/errors/599beab51b945016. Report an issue: GitHub.

Appendix: source

Thrown at cli/command/container/opts.go:816

			if ep == nil || reflect.ValueOf(*ep).IsZero() {
				continue
			}
		}
		endpoints[n.Target] = ep
	}
	if hasUserDefined && hasNonUserDefined {
		return nil, invalidParameter(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 invalidParameter(errors.New("conflicting options: cannot specify both --network-alias and per-network alias"))
	}
	if len(n.Links) > 0 && copts.links.Len() > 0 {
		return invalidParameter(errors.New("conflicting options: cannot specify both --link and per-network links"))
	}
	if n.IPv4Address.IsValid() && copts.ipv4Address != nil {
		return invalidParameter(errors.New("conflicting options: cannot specify both --ip and per-network IPv4 address"))
	}
	if n.IPv6Address.IsValid() && copts.ipv6Address != nil {
		return invalidParameter(errors.New("conflicting options: cannot specify both --ip6 and per-network IPv6 address"))
	}
	if n.MacAddress != "" && copts.macAddress != "" {
		return invalidParameter(errors.New("conflicting options: cannot specify both --mac-address and per-network MAC address"))
	}
	if len(n.LinkLocalIPs) > 0 && copts.linkLocalIPs.Len() > 0 {
		return invalidParameter(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,

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