system df to show podman disk usage

Signed-off-by: Qi Wang <qiwan@redhat.com>

1 files changed, 639 insertions, 0 deletions

diff --git a/cmd/podman/system_df.go b/cmd/podman/system_df.go
new file mode 100644
index 000000000..183c5a7dd
--- /dev/null
+++ b/cmd/podman/system_df.go
@@ -0,0 +1,639 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/containers/buildah/pkg/formats"
+	"github.com/containers/libpod/cmd/podman/cliconfig"
+	"github.com/containers/libpod/cmd/podman/libpodruntime"
+	"github.com/containers/libpod/libpod"
+	"github.com/containers/libpod/libpod/image"
+	units "github.com/docker/go-units"
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+)
+
+var (
+	dfSystemCommand     cliconfig.SystemDfValues
+	dfSystemDescription = `
+	podman system df
+
+	Show podman disk usage
+	`
+	_dfSystemCommand = &cobra.Command{
+		Use:   "df",
+		Short: "Show podman disk usage",
+		Long:  dfSystemDescription,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			dfSystemCommand.GlobalFlags = MainGlobalOpts
+			return dfSystemCmd(&dfSystemCommand)
+		},
+	}
+)
+
+type dfMetaData struct {
+	images                   []*image.Image
+	containers               []*libpod.Container
+	activeContainers         map[string]*libpod.Container
+	imagesUsedbyCtrMap       map[string][]*libpod.Container
+	imagesUsedbyActiveCtr    map[string][]*libpod.Container
+	volumes                  []*libpod.Volume
+	volumeUsedByContainerMap map[string][]*libpod.Container
+}
+
+type systemDfDiskUsage struct {
+	Type        string
+	Total       int
+	Active      int
+	Size        string
+	Reclaimable string
+}
+
+type imageVerboseDiskUsage struct {
+	Repository string
+	Tag        string
+	ImageID    string
+	Created    string
+	Size       string
+	SharedSize string
+	UniqueSize string
+	Containers int
+}
+
+type containerVerboseDiskUsage struct {
+	ContainerID  string
+	Image        string
+	Command      string
+	LocalVolumes int
+	Size         string
+	Created      string
+	Status       string
+	Names        string
+}
+
+type volumeVerboseDiskUsage struct {
+	VolumeName string
+	Links      int
+	Size       string
+}
+
+const systemDfDefaultFormat string = "table {{.Type}}\t{{.Total}}\t{{.Active}}\t{{.Size}}\t{{.Reclaimable}}"
+
+func init() {
+	dfSystemCommand.Command = _dfSystemCommand
+	dfSystemCommand.SetUsageTemplate(UsageTemplate())
+	flags := dfSystemCommand.Flags()
+	flags.BoolVarP(&dfSystemCommand.Verbose, "verbose", "v", false, "Show detailed information on space usage")
+	flags.StringVar(&dfSystemCommand.Format, "format", "", "Pretty-print images using a Go template")
+}
+
+func dfSystemCmd(c *cliconfig.SystemDfValues) error {
+	runtime, err := libpodruntime.GetRuntime(&c.PodmanCommand)
+	if err != nil {
+		return errors.Wrapf(err, "Could not get runtime")
+	}
+	defer runtime.Shutdown(false)
+
+	ctx := getContext()
+
+	metaData, err := getDfMetaData(ctx, runtime)
+	if err != nil {
+		return errors.Wrapf(err, "error getting disk usage data")
+	}
+
+	if c.Verbose {
+		err := verboseOutput(ctx, metaData)
+		if err != nil {
+			return err
+		}
+		return nil
+	}
+
+	systemDfDiskUsages, err := getDiskUsage(ctx, runtime, metaData)
+	if err != nil {
+		return errors.Wrapf(err, "error getting output of system df")
+	}
+	format := systemDfDefaultFormat
+	if c.Format != "" {
+		format = strings.Replace(c.Format, `\t`, "\t", -1)
+	}
+	generateSysDfOutput(systemDfDiskUsages, format)
+	return nil
+}
+
+func generateSysDfOutput(systemDfDiskUsages []systemDfDiskUsage, format string) {
+	var systemDfHeader = map[string]string{
+		"Type":        "TYPE",
+		"Total":       "TOTAL",
+		"Active":      "ACTIVE",
+		"Size":        "SIZE",
+		"Reclaimable": "RECLAIMABLE",
+	}
+	out := formats.StdoutTemplateArray{Output: systemDfDiskUsageToGeneric(systemDfDiskUsages), Template: format, Fields: systemDfHeader}
+	formats.Writer(out).Out()
+}
+
+func getDiskUsage(ctx context.Context, runtime *libpod.Runtime, metaData dfMetaData) ([]systemDfDiskUsage, error) {
+	imageDiskUsage, err := getImageDiskUsage(ctx, metaData.images, metaData.imagesUsedbyCtrMap, metaData.imagesUsedbyActiveCtr)
+	if err != nil {
+		return nil, errors.Wrapf(err, "error getting disk usage of images")
+	}
+	containerDiskUsage, err := getContainerDiskUsage(metaData.containers, metaData.activeContainers)
+	if err != nil {
+		return nil, errors.Wrapf(err, "error getting disk usage of containers")
+	}
+	volumeDiskUsage, err := getVolumeDiskUsage(metaData.volumes, metaData.volumeUsedByContainerMap)
+	if err != nil {
+		return nil, errors.Wrapf(err, "error getting disk usage of volumess")
+	}
+
+	systemDfDiskUsages := []systemDfDiskUsage{imageDiskUsage, containerDiskUsage, volumeDiskUsage}
+	return systemDfDiskUsages, nil
+}
+
+func getDfMetaData(ctx context.Context, runtime *libpod.Runtime) (dfMetaData, error) {
+	var metaData dfMetaData
+	images, err := runtime.ImageRuntime().GetImages()
+	if err != nil {
+		return metaData, errors.Wrapf(err, "unable to get images")
+	}
+	containers, err := runtime.GetAllContainers()
+	if err != nil {
+		return metaData, errors.Wrapf(err, "error getting all containers")
+	}
+	volumes, err := runtime.GetAllVolumes()
+	if err != nil {
+		return metaData, errors.Wrap(err, "error getting all volumes")
+	}
+	activeContainers, err := activeContainers(containers)
+	if err != nil {
+		return metaData, errors.Wrapf(err, "error getting active containers")
+	}
+	imagesUsedbyCtrMap, imagesUsedbyActiveCtr, err := imagesUsedbyCtr(containers, activeContainers)
+	if err != nil {
+		return metaData, errors.Wrapf(err, "error getting getting images used by containers")
+	}
+	metaData = dfMetaData{
+		images:                   images,
+		containers:               containers,
+		activeContainers:         activeContainers,
+		imagesUsedbyCtrMap:       imagesUsedbyCtrMap,
+		imagesUsedbyActiveCtr:    imagesUsedbyActiveCtr,
+		volumes:                  volumes,
+		volumeUsedByContainerMap: volumeUsedByContainer(containers),
+	}
+	return metaData, nil
+}
+
+func imageUniqueSize(ctx context.Context, images []*image.Image) (map[string]uint64, error) {
+	imgUniqueSizeMap := make(map[string]uint64)
+	for _, img := range images {
+		parentImg := img
+		for {
+			next, err := parentImg.GetParent()
+			if err != nil {
+				return nil, errors.Wrapf(err, "error getting parent of image %s", parentImg.ID())
+			}
+			if next == nil {
+				break
+			}
+			parentImg = next
+		}
+		imgSize, err := img.Size(ctx)
+		if err != nil {
+			return nil, err
+		}
+		if img.ID() == parentImg.ID() {
+			imgUniqueSizeMap[img.ID()] = *imgSize
+		} else {
+			parentImgSize, err := parentImg.Size(ctx)
+			if err != nil {
+				return nil, errors.Wrapf(err, "error getting size of parent image %s", parentImg.ID())
+			}
+			imgUniqueSizeMap[img.ID()] = *imgSize - *parentImgSize
+		}
+	}
+	return imgUniqueSizeMap, nil
+}
+
+func getImageDiskUsage(ctx context.Context, images []*image.Image, imageUsedbyCintainerMap map[string][]*libpod.Container, imageUsedbyActiveContainerMap map[string][]*libpod.Container) (systemDfDiskUsage, error) {
+	var (
+		numberOfImages       int
+		sumSize              uint64
+		numberOfActiveImages int
+		unreclaimableSize    uint64
+		imageDiskUsage       systemDfDiskUsage
+		reclaimableStr       string
+	)
+
+	imgUniqueSizeMap, err := imageUniqueSize(ctx, images)
+	if err != nil {
+		return imageDiskUsage, errors.Wrapf(err, "error getting unique size of images")
+	}
+
+	for _, img := range images {
+
+		unreclaimableSize += imageUsedSize(img, imgUniqueSizeMap, imageUsedbyCintainerMap, imageUsedbyActiveContainerMap)
+
+		isParent, err := img.IsParent()
+		if err != nil {
+			return imageDiskUsage, err
+		}
+		parent, err := img.GetParent()
+		if err != nil {
+			return imageDiskUsage, errors.Wrapf(err, "error getting parent of image %s", img.ID())
+		}
+		if isParent && parent != nil {
+			continue
+		}
+		numberOfImages++
+		if _, isActive := imageUsedbyCintainerMap[img.ID()]; isActive {
+			numberOfActiveImages++
+		}
+
+		if !isParent {
+			size, err := img.Size(ctx)
+			if err != nil {
+				return imageDiskUsage, errors.Wrapf(err, "error getting disk usage of image %s", img.ID())
+			}
+			sumSize += *size
+		}
+
+	}
+	sumSizeStr := units.HumanSizeWithPrecision(float64(sumSize), 3)
+	reclaimable := sumSize - unreclaimableSize
+	if sumSize != 0 {
+		reclaimableStr = fmt.Sprintf("%s (%v%%)", units.HumanSizeWithPrecision(float64(reclaimable), 3), 100*reclaimable/sumSize)
+	} else {
+		reclaimableStr = fmt.Sprintf("%s (%v%%)", units.HumanSizeWithPrecision(float64(reclaimable), 3), 0)
+	}
+	imageDiskUsage = systemDfDiskUsage{
+		Type:        "Images",
+		Total:       numberOfImages,
+		Active:      numberOfActiveImages,
+		Size:        sumSizeStr,
+		Reclaimable: reclaimableStr,
+	}
+	return imageDiskUsage, nil
+}
+
+func imageUsedSize(img *image.Image, imgUniqueSizeMap map[string]uint64, imageUsedbyCintainerMap map[string][]*libpod.Container, imageUsedbyActiveContainerMap map[string][]*libpod.Container) uint64 {
+	var usedSize uint64
+	imgUnique := imgUniqueSizeMap[img.ID()]
+	if _, isCtrActive := imageUsedbyActiveContainerMap[img.ID()]; isCtrActive {
+		return imgUnique
+	}
+	containers := imageUsedbyCintainerMap[img.ID()]
+	for _, ctr := range containers {
+		if len(ctr.UserVolumes()) > 0 {
+			usedSize += imgUnique
+			return usedSize
+		}
+	}
+	return usedSize
+}
+
+func imagesUsedbyCtr(containers []*libpod.Container, activeContainers map[string]*libpod.Container) (map[string][]*libpod.Container, map[string][]*libpod.Container, error) {
+	imgCtrMap := make(map[string][]*libpod.Container)
+	imgActiveCtrMap := make(map[string][]*libpod.Container)
+	for _, ctr := range containers {
+		imgID, _ := ctr.Image()
+		imgCtrMap[imgID] = append(imgCtrMap[imgID], ctr)
+		if _, isActive := activeContainers[ctr.ID()]; isActive {
+			imgActiveCtrMap[imgID] = append(imgActiveCtrMap[imgID], ctr)
+		}
+	}
+	return imgCtrMap, imgActiveCtrMap, nil
+}
+
+func getContainerDiskUsage(containers []*libpod.Container, activeContainers map[string]*libpod.Container) (systemDfDiskUsage, error) {
+	var (
+		sumSize           int64
+		unreclaimableSize int64
+		reclaimableStr    string
+	)
+	for _, ctr := range containers {
+		size, err := ctr.RWSize()
+		if err != nil {
+			return systemDfDiskUsage{}, errors.Wrapf(err, "error getting size of container %s", ctr.ID())
+		}
+		sumSize += size
+	}
+	for _, activeCtr := range activeContainers {
+		size, err := activeCtr.RWSize()
+		if err != nil {
+			return systemDfDiskUsage{}, errors.Wrapf(err, "error getting size of active container %s", activeCtr.ID())
+		}
+		unreclaimableSize += size
+	}
+	if sumSize == 0 {
+		reclaimableStr = fmt.Sprintf("%s (%v%%)", units.HumanSizeWithPrecision(0, 3), 0)
+	} else {
+		reclaimable := sumSize - unreclaimableSize
+		reclaimableStr = fmt.Sprintf("%s (%v%%)", units.HumanSizeWithPrecision(float64(reclaimable), 3), 100*reclaimable/sumSize)
+	}
+	containerDiskUsage := systemDfDiskUsage{
+		Type:        "Containers",
+		Total:       len(containers),
+		Active:      len(activeContainers),
+		Size:        units.HumanSizeWithPrecision(float64(sumSize), 3),
+		Reclaimable: reclaimableStr,
+	}
+	return containerDiskUsage, nil
+}
+
+func ctrIsActive(ctr *libpod.Container) (bool, error) {
+	state, err := ctr.State()
+	if err != nil {
+		return false, err
+	}
+	return state == libpod.ContainerStatePaused || state == libpod.ContainerStateRunning, nil
+}
+
+func activeContainers(containers []*libpod.Container) (map[string]*libpod.Container, error) {
+	activeContainers := make(map[string]*libpod.Container)
+	for _, aCtr := range containers {
+		isActive, err := ctrIsActive(aCtr)
+		if err != nil {
+			return nil, err
+		}
+		if isActive {
+			activeContainers[aCtr.ID()] = aCtr
+		}
+	}
+	return activeContainers, nil
+}
+
+func getVolumeDiskUsage(volumes []*libpod.Volume, volumeUsedByContainerMap map[string][]*libpod.Container) (systemDfDiskUsage, error) {
+	var (
+		sumSize           int64
+		unreclaimableSize int64
+		reclaimableStr    string
+	)
+	for _, volume := range volumes {
+		size, err := volumeSize(volume)
+		if err != nil {
+			return systemDfDiskUsage{}, errors.Wrapf(err, "error getting size of volime %s", volume.Name())
+		}
+		sumSize += size
+		if _, exist := volumeUsedByContainerMap[volume.Name()]; exist {
+			unreclaimableSize += size
+		}
+	}
+	reclaimable := sumSize - unreclaimableSize
+	if sumSize != 0 {
+		reclaimableStr = fmt.Sprintf("%s (%v%%)", units.HumanSizeWithPrecision(float64(reclaimable), 3), 100*reclaimable/sumSize)
+	} else {
+		reclaimableStr = fmt.Sprintf("%s (%v%%)", units.HumanSizeWithPrecision(float64(reclaimable), 3), 0)
+	}
+	volumesDiskUsage := systemDfDiskUsage{
+		Type:        "Local Volumes",
+		Total:       len(volumes),
+		Active:      len(volumeUsedByContainerMap),
+		Size:        units.HumanSizeWithPrecision(float64(sumSize), 3),
+		Reclaimable: reclaimableStr,
+	}
+	return volumesDiskUsage, nil
+}
+
+func volumeUsedByContainer(containers []*libpod.Container) map[string][]*libpod.Container {
+	volumeUsedByContainerMap := make(map[string][]*libpod.Container)
+	for _, ctr := range containers {
+
+		ctrVolumes := ctr.UserVolumes()
+		for _, ctrVolume := range ctrVolumes {
+			volumeUsedByContainerMap[ctrVolume] = append(volumeUsedByContainerMap[ctrVolume], ctr)
+		}
+	}
+	return volumeUsedByContainerMap
+}
+
+func volumeSize(volume *libpod.Volume) (int64, error) {
+	var size int64
+	err := filepath.Walk(volume.MountPoint(), func(path string, info os.FileInfo, err error) error {
+		if err == nil && !info.IsDir() {
+			size += info.Size()
+		}
+		return err
+	})
+	return size, err
+}
+
+func getImageVerboseDiskUsage(ctx context.Context, images []*image.Image, imagesUsedbyCtr map[string][]*libpod.Container) ([]imageVerboseDiskUsage, error) {
+	var imagesVerboseDiskUsage []imageVerboseDiskUsage
+	imgUniqueSizeMap, err := imageUniqueSize(ctx, images)
+	if err != nil {
+		return imagesVerboseDiskUsage, errors.Wrapf(err, "error getting unique size of images")
+	}
+	for _, img := range images {
+		isParent, err := img.IsParent()
+		if err != nil {
+			return imagesVerboseDiskUsage, errors.Wrapf(err, "error checking if %s is a parent images", img.ID())
+		}
+		parent, err := img.GetParent()
+		if err != nil {
+			return imagesVerboseDiskUsage, errors.Wrapf(err, "error getting parent of image %s", img.ID())
+		}
+		if isParent && parent != nil {
+			continue
+		}
+		size, err := img.Size(ctx)
+		if err != nil {
+			return imagesVerboseDiskUsage, errors.Wrapf(err, "error getting size of image %s", img.ID())
+		}
+		numberOfContainers := 0
+		if ctrs, exist := imagesUsedbyCtr[img.ID()]; exist {
+			numberOfContainers = len(ctrs)
+		}
+		var repo string
+		var tag string
+		if len(img.Names()) == 0 {
+			repo = "<none>"
+			tag = "<none>"
+		}
+		repopairs, err := image.ReposToMap([]string{img.Names()[0]})
+		if err != nil {
+			logrus.Errorf("error finding tag/digest for %s", img.ID())
+		}
+		for reponame, tags := range repopairs {
+			for _, tagname := range tags {
+				repo = reponame
+				tag = tagname
+			}
+		}
+
+		imageVerbosedf := imageVerboseDiskUsage{
+			Repository: repo,
+			Tag:        tag,
+			ImageID:    shortID(img.ID()),
+			Created:    units.HumanDuration(time.Since((img.Created().Local()))) + " ago",
+			Size:       units.HumanSizeWithPrecision(float64(*size), 3),
+			SharedSize: units.HumanSizeWithPrecision(float64(*size-imgUniqueSizeMap[img.ID()]), 3),
+			UniqueSize: units.HumanSizeWithPrecision(float64(imgUniqueSizeMap[img.ID()]), 3),
+			Containers: numberOfContainers,
+		}
+		imagesVerboseDiskUsage = append(imagesVerboseDiskUsage, imageVerbosedf)
+	}
+	return imagesVerboseDiskUsage, nil
+}
+
+func getContainerVerboseDiskUsage(containers []*libpod.Container) (containersVerboseDiskUsage []containerVerboseDiskUsage, err error) {
+	for _, ctr := range containers {
+		imgID, _ := ctr.Image()
+		size, err := ctr.RWSize()
+		if err != nil {
+			return containersVerboseDiskUsage, errors.Wrapf(err, "error getting size of container %s", ctr.ID())
+		}
+		state, err := ctr.State()
+		if err != nil {
+			return containersVerboseDiskUsage, errors.Wrapf(err, "error getting the state of container %s", ctr.ID())
+		}
+
+		ctrVerboseData := containerVerboseDiskUsage{
+			ContainerID:  shortID(ctr.ID()),
+			Image:        shortImageID(imgID),
+			Command:      strings.Join(ctr.Command(), " "),
+			LocalVolumes: len(ctr.UserVolumes()),
+			Size:         units.HumanSizeWithPrecision(float64(size), 3),
+			Created:      units.HumanDuration(time.Since(ctr.CreatedTime().Local())) + "ago",
+			Status:       state.String(),
+			Names:        ctr.Name(),
+		}
+		containersVerboseDiskUsage = append(containersVerboseDiskUsage, ctrVerboseData)
+
+	}
+	return containersVerboseDiskUsage, nil
+}
+
+func getVolumeVerboseDiskUsage(volumes []*libpod.Volume, volumeUsedByContainerMap map[string][]*libpod.Container) (volumesVerboseDiskUsage []volumeVerboseDiskUsage, err error) {
+	for _, vol := range volumes {
+		volSize, err := volumeSize(vol)
+		if err != nil {
+			return volumesVerboseDiskUsage, errors.Wrapf(err, "error getting size of volume %s", vol.Name())
+		}
+		links := 0
+		if linkCtr, exist := volumeUsedByContainerMap[vol.Name()]; exist {
+			links = len(linkCtr)
+		}
+		volumeVerboseData := volumeVerboseDiskUsage{
+			VolumeName: vol.Name(),
+			Links:      links,
+			Size:       units.HumanSizeWithPrecision(float64(volSize), 3),
+		}
+		volumesVerboseDiskUsage = append(volumesVerboseDiskUsage, volumeVerboseData)
+	}
+	return volumesVerboseDiskUsage, nil
+}
+
+func imagesVerboseOutput(ctx context.Context, metaData dfMetaData) error {
+	var imageVerboseHeader = map[string]string{
+		"Repository": "REPOSITORY",
+		"Tag":        "TAG",
+		"ImageID":    "IMAGE ID",
+		"Created":    "CREATED",
+		"Size":       "SIZE",
+		"SharedSize": "SHARED SIZE",
+		"UniqueSize": "UNQUE SIZE",
+		"Containers": "CONTAINERS",
+	}
+	imagesVerboseDiskUsage, err := getImageVerboseDiskUsage(ctx, metaData.images, metaData.imagesUsedbyCtrMap)
+	if err != nil {
+		return errors.Wrapf(err, "error getting verbose output of images")
+	}
+	os.Stderr.WriteString("Images space usage:\n\n")
+	out := formats.StdoutTemplateArray{Output: systemDfImageVerboseDiskUsageToGeneric(imagesVerboseDiskUsage), Template: "table {{.Repository}}\t{{.Tag}}\t{{.ImageID}}\t{{.Created}}\t{{.Size}}\t{{.SharedSize}}\t{{.UniqueSize}}\t{{.Containers}}", Fields: imageVerboseHeader}
+	formats.Writer(out).Out()
+	return nil
+}
+
+func containersVerboseOutput(ctx context.Context, metaData dfMetaData) error {
+	var containerVerboseHeader = map[string]string{
+		"ContainerID":  "CONTAINER ID ",
+		"Image":        "IMAGE",
+		"Command":      "COMMAND",
+		"LocalVolumes": "LOCAL VOLUMES",
+		"Size":         "SIZE",
+		"Created":      "CREATED",
+		"Status":       "STATUS",
+		"Names":        "NAMES",
+	}
+	containersVerboseDiskUsage, err := getContainerVerboseDiskUsage(metaData.containers)
+	if err != nil {
+		return errors.Wrapf(err, "error getting verbose output of containers")
+	}
+	os.Stderr.WriteString("\nContainers space usage:\n\n")
+	out := formats.StdoutTemplateArray{Output: systemDfContainerVerboseDiskUsageToGeneric(containersVerboseDiskUsage), Template: "table {{.ContainerID}}\t{{.Image}}\t{{.Command}}\t{{.LocalVolumes}}\t{{.Size}}\t{{.Created}}\t{{.Status}}\t{{.Names}}", Fields: containerVerboseHeader}
+	formats.Writer(out).Out()
+	return nil
+}
+
+func volumesVerboseOutput(ctx context.Context, metaData dfMetaData) error {
+	var volumeVerboseHeader = map[string]string{
+		"VolumeName": "VOLUME NAME",
+		"Links":      "LINKS",
+		"Size":       "SIZE",
+	}
+	volumesVerboseDiskUsage, err := getVolumeVerboseDiskUsage(metaData.volumes, metaData.volumeUsedByContainerMap)
+	if err != nil {
+		return errors.Wrapf(err, "error getting verbose ouput of volumes")
+	}
+	os.Stderr.WriteString("\nLocal Volumes space usage:\n\n")
+	out := formats.StdoutTemplateArray{Output: systemDfVolumeVerboseDiskUsageToGeneric(volumesVerboseDiskUsage), Template: "table {{.VolumeName}}\t{{.Links}}\t{{.Size}}", Fields: volumeVerboseHeader}
+	formats.Writer(out).Out()
+	return nil
+}
+
+func verboseOutput(ctx context.Context, metaData dfMetaData) error {
+	if err := imagesVerboseOutput(ctx, metaData); err != nil {
+		return err
+	}
+	if err := containersVerboseOutput(ctx, metaData); err != nil {
+		return err
+	}
+	if err := volumesVerboseOutput(ctx, metaData); err != nil {
+		return err
+	}
+	return nil
+}
+
+func systemDfDiskUsageToGeneric(diskUsages []systemDfDiskUsage) (out []interface{}) {
+	for _, usage := range diskUsages {
+		out = append(out, interface{}(usage))
+	}
+	return out
+}
+
+func systemDfImageVerboseDiskUsageToGeneric(diskUsages []imageVerboseDiskUsage) (out []interface{}) {
+	for _, usage := range diskUsages {
+		out = append(out, interface{}(usage))
+	}
+	return out
+}
+
+func systemDfContainerVerboseDiskUsageToGeneric(diskUsages []containerVerboseDiskUsage) (out []interface{}) {
+	for _, usage := range diskUsages {
+		out = append(out, interface{}(usage))
+	}
+	return out
+}
+
+func systemDfVolumeVerboseDiskUsageToGeneric(diskUsages []volumeVerboseDiskUsage) (out []interface{}) {
+	for _, usage := range diskUsages {
+		out = append(out, interface{}(usage))
+	}
+	return out
+}
+
+func shortImageID(id string) string {
+	const imageIDTruncLength int = 4
+	if len(id) > imageIDTruncLength {
+		return id[:imageIDTruncLength]
+	}
+	return id
+}