volume options are incompatible with type tmpfs

Error message

volume options are incompatible with type tmpfs

What it means

Returned by handleTmpfsToMount (cli/compose/convert/volume.go:155-156). nocopy/subpath are named-volume options and have no analogue for an in-memory tmpfs filesystem, so the converter rejects a `volume:` block on a tmpfs entry.

Solutions

Remove the `volume:` options block from the tmpfs entry.
If nocopy/subpath was required, restore `type: volume` and reference a named source.

Example fix

# before
volumes:
  - type: tmpfs
    target: /cache
    volume:
      nocopy: true

# after
volumes:
  - type: tmpfs
    target: /cache

Defensive patterns

Strategy: validation

Validate before calling

for i, v := range serviceVolumes {
    if v.Type == "tmpfs" && v.Volume != nil {
        return fmt.Errorf("service volume[%d] target=%q: type tmpfs must not declare a volume block", i, v.Target)
    }
}

Try / catch

mounts, err := convert.Volumes(serviceVolumes, stackVolumes, namespace)
if err != nil && strings.Contains(err.Error(), "volume options are incompatible with type tmpfs") {
    return fmt.Errorf("compose config error: %w (remove the volume: block from the tmpfs entry)", err)
}

Prevention

Do not derive a tmpfs entry from a named-volume template without deleting the volume block.
Run `docker compose config` to surface cross-type option conflicts.

When it happens

Trigger: ServiceVolumeConfig with Type=="tmpfs" and Volume!=nil passed to convertVolumeToMount().

Common situations: Reusing a named-volume entry and flipping its type to tmpfs; copy-paste between volume definitions.

Related errors

AI-assisted analysis of docker/cli@4f84911bfe (2026-08-07). Data as JSON: /api/errors/058b060842230a99. Report an issue: GitHub.

Appendix: source

Thrown at cli/compose/convert/volume.go:156

	if volume.Bind != nil {
		result.BindOptions = &mount.BindOptions{
			Propagation: mount.Propagation(volume.Bind.Propagation),
		}
	}
	return result, nil
}

func handleTmpfsToMount(volume composetypes.ServiceVolumeConfig) (mount.Mount, error) {
	result := createMountFromVolume(volume)

	if volume.Source != "" {
		return mount.Mount{}, errors.New("invalid tmpfs source, source must be empty")
	}
	if volume.Bind != nil {
		return mount.Mount{}, errors.New("bind options are incompatible with type tmpfs")
	}
	if volume.Volume != nil {
		return mount.Mount{}, errors.New("volume options are incompatible with type tmpfs")
	}
	if volume.Image != nil {
		return mount.Mount{}, errors.New("image options are incompatible with type tmpfs")
	}
	if volume.Cluster != nil {
		return mount.Mount{}, errors.New("cluster options are incompatible with type tmpfs")
	}
	if volume.Tmpfs != nil {
		result.TmpfsOptions = &mount.TmpfsOptions{
			SizeBytes: volume.Tmpfs.Size,
		}
	}
	return result, nil
}

func handleNpipeToMount(volume composetypes.ServiceVolumeConfig) (mount.Mount, error) {
	result := createMountFromVolume(volume)

View on GitHub (pinned to 4f84911bfe)