Add --volumes-from flag to podman run and create

podman now supports --volumes-from flag, which allows users
to add all the volumes an existing container has to a new one.

Signed-off-by: umohnani8 <umohnani@redhat.com>

Closes: #931
Approved by: mheon

cmd/podman/create.go

@@ -302,6 +302,10 @@ func parseCreateOpts(ctx context.Context, c *cli.Context, runtime *libpod.Runtim
 		return nil, err
 	}
 
+	if err = parseVolumesFrom(c.StringSlice("volumes-from")); err != nil {
+		return nil, err
+	}
+
 	tty := c.Bool("tty")
 
 	pidMode := container.PidMode(c.String("pid"))
@@ -596,6 +600,7 @@ func parseCreateOpts(ctx context.Context, c *cli.Context, runtime *libpod.Runtim
 		Volumes:     c.StringSlice("volume"),
 		WorkDir:     workDir,
 		Rootfs:      rootfs,
+		VolumesFrom: c.StringSlice("volumes-from"),
 	}
 
 	if !config.Privileged {

cmd/podman/create_cli.go

@@ -75,9 +75,6 @@ func addWarning(warnings []string, msg string) []string {
 }
 
 func parseVolumes(volumes []string) error {
-	if len(volumes) == 0 {
-		return nil
-	}
 	for _, volume := range volumes {
 		arr := strings.SplitN(volume, ":", 3)
 		if len(arr) < 2 {
@@ -98,6 +95,21 @@ func parseVolumes(volumes []string) error {
 	return nil
 }
 
+func parseVolumesFrom(volumesFrom []string) error {
+	for _, vol := range volumesFrom {
+		arr := strings.SplitN(vol, ":", 2)
+		if len(arr) == 2 {
+			if strings.Contains(arr[1], "Z") || strings.Contains(arr[1], "private") || strings.Contains(arr[1], "slave") || strings.Contains(arr[1], "shared") {
+				return errors.Errorf("invalid options %q, can only specify 'ro', 'rw', and 'z", arr[1])
+			}
+			if err := validateVolumeOpts(arr[1]); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
 func validateVolumeHostDir(hostDir string) error {
 	if !filepath.IsAbs(hostDir) {
 		return errors.Errorf("invalid host path, must be an absolute path %q", hostDir)
@@ -121,20 +133,20 @@ func validateVolumeOpts(option string) error {
 	for _, opt := range options {
 		switch opt {
 		case "rw", "ro":
+			foundRWRO++
 			if foundRWRO > 1 {
 				return errors.Errorf("invalid options %q, can only specify 1 'rw' or 'ro' option", option)
 			}
-			foundRWRO++
 		case "z", "Z":
+			foundLabelChange++
 			if foundLabelChange > 1 {
 				return errors.Errorf("invalid options %q, can only specify 1 'z' or 'Z' option", option)
 			}
-			foundLabelChange++
 		case "private", "rprivate", "shared", "rshared", "slave", "rslave":
+			foundRootPropagation++
 			if foundRootPropagation > 1 {
 				return errors.Errorf("invalid options %q, can only specify 1 '[r]shared', '[r]private' or '[r]slave' option", option)
 			}
-			foundRootPropagation++
 		default:
 			return errors.Errorf("invalid option type %q", option)
 		}

docs/podman-create.1.md

@@ -654,6 +654,40 @@ change propagation properties of source mount. Say `/` is source mount for
 To disable automatic copying of data from the container path to the volume, use
 the `nocopy` flag. The `nocopy` flag can be set on bind mounts and named volumes.
 
+**--volumes-from**[=*CONTAINER*[:*OPTIONS*]]
+
+Mount volumes from the specified container(s).
+*OPTIONS* is a comma delimited list with the following available elements:
+
+* [rw|ro]
+* z
+
+Mounts already mounted volumes from a source container onto another
+container. You must supply the source's container-id or container-name.
+To share a volume, use the --volumes-from option when running
+the target container. You can share volumes even if the source container
+is not running.
+
+By default, podman mounts the volumes in the same mode (read-write or
+read-only) as it is mounted in the source container. Optionally, you
+can change this by suffixing the container-id with either the `ro` or
+`rw` keyword.
+
+Labeling systems like SELinux require that proper labels are placed on volume
+content mounted into a container. Without a label, the security system might
+prevent the processes running inside the container from using the content. By
+default, podman does not change the labels set by the OS.
+
+To change a label in the container context, you can add `z` to the volume mount.
+This suffix tells podman to relabel file objects on the shared volumes. The `z`
+option tells podman that two containers share the volume content. As a result,
+podman labels the content with a shared content label. Shared volume labels allow
+all containers to read/write content.
+
+If the location of the volume from the source container overlaps with
+data residing on a target container, then the volume hides
+that data on the target.
+
 **-w**, **--workdir**=""
 
 Working directory inside the container

docs/podman-run.1.md

@@ -686,6 +686,40 @@ change propagation properties of source mount. Say `/` is source mount for
 To disable automatic copying of data from the container path to the volume, use
 the `nocopy` flag. The `nocopy` flag can be set on bind mounts and named volumes.
 
+**--volumes-from**[=*CONTAINER*[:*OPTIONS*]]
+
+Mount volumes from the specified container(s).
+*OPTIONS* is a comma delimited list with the following available elements:
+
+* [rw|ro]
+* z
+
+Mounts already mounted volumes from a source container onto another
+container. You must supply the source's container-id or container-name.
+To share a volume, use the --volumes-from option when running
+the target container. You can share volumes even if the source container
+is not running.
+
+By default, podman mounts the volumes in the same mode (read-write or
+read-only) as it is mounted in the source container. Optionally, you
+can change this by suffixing the container-id with either the `ro` or
+`rw` keyword.
+
+Labeling systems like SELinux require that proper labels are placed on volume
+content mounted into a container. Without a label, the security system might
+prevent the processes running inside the container from using the content. By
+default, podman does not change the labels set by the OS.
+
+To change a label in the container context, you can add `z` to the volume mount.
+This suffix tells podman to relabel file objects on the shared volumes. The `z`
+option tells podman that two containers share the volume content. As a result,
+podman labels the content with a shared content label. Shared volume labels allow
+all containers to read/write content.
+
+If the location of the volume from the source container overlaps with
+data residing on a target container, then the volume hides
+that data on the target.
+
 **-w**, **--workdir**=""
 
 Working directory inside the container

libpod/container.go

@@ -313,6 +313,9 @@ type ContainerConfig struct {
 	// ExitCommand is the container's exit command.
 	// This Command will be executed when the container exits
 	ExitCommand []string `json:"exitCommand,omitempty"`
+	// LocalVolumes are the built-in volumes we get from the --volumes-from flag
+	// It picks up the built-in volumes of the container used by --volumes-from
+	LocalVolumes []string
 }
 
 // ContainerStatus returns a string representation for users

libpod/container_internal.go

@@ -1108,7 +1108,7 @@ func (c *Container) generateHosts() (string, error) {
 	return c.writeStringToRundir("hosts", hosts)
 }
 
-func (c *Container) addImageVolumes(ctx context.Context, g *generate.Generator) error {
+func (c *Container) addLocalVolumes(ctx context.Context, g *generate.Generator) error {
 	mountPoint := c.state.Mountpoint
 	if !c.state.Mounted {
 		return errors.Wrapf(ErrInternal, "container is not mounted")
@@ -1121,6 +1121,17 @@ func (c *Container) addImageVolumes(ctx context.Context, g *generate.Generator)
 	if err != nil {
 		return err
 	}
+	// Add the built-in volumes of the container passed in to --volumes-from
+	for _, vol := range c.config.LocalVolumes {
+		if imageData.ContainerConfig.Volumes == nil {
+			imageData.ContainerConfig.Volumes = map[string]struct{}{
+				vol: {},
+			}
+		} else {
+			imageData.ContainerConfig.Volumes[vol] = struct{}{}
+		}
+	}
+
 	for k := range imageData.ContainerConfig.Volumes {
 		mount := spec.Mount{
 			Destination: k,

libpod/container_internal_linux.go

@@ -127,7 +127,7 @@ func (c *Container) generateSpec(ctx context.Context) (*spec.Spec, error) {
 
 	// Bind builtin image volumes
 	if c.config.Rootfs == "" && c.config.ImageVolumes {
-		if err := c.addImageVolumes(ctx, &g); err != nil {
+		if err := c.addLocalVolumes(ctx, &g); err != nil {
 			return nil, errors.Wrapf(err, "error mounting image volumes")
 		}
 	}

libpod/options.go

@@ -885,6 +885,24 @@ func WithUserVolumes(volumes []string) CtrCreateOption {
 	}
 }
 
+// WithLocalVolumes sets the built-in volumes of the container retrieved
+// from a container passed in to the --volumes-from flag.
+// This stores the built-in volume information in the ContainerConfig so we can
+// add them when creating the container.
+func WithLocalVolumes(volumes []string) CtrCreateOption {
+	return func(ctr *Container) error {
+		if ctr.valid {
+			return ErrCtrFinalized
+		}
+
+		if volumes != nil {
+			ctr.config.LocalVolumes = append(ctr.config.LocalVolumes, volumes...)
+		}
+
+		return nil
+	}
+}
+
 // WithEntrypoint sets the entrypoint of the container.
 // This is not used to change the container's spec, but will instead be used
 // during commit to populate the entrypoint of the new image.

pkg/spec/createconfig.go

@@ -1,6 +1,7 @@
 package createconfig
 
 import (
+	"encoding/json"
 	"os"
 	"strconv"
 	"strings"
@@ -123,6 +124,7 @@ type CreateConfig struct {
 	User               string               //user
 	UtsMode            container.UTSMode    //uts
 	Volumes            []string             //volume
+	VolumesFrom        []string
 	WorkDir            string //workdir
 	MountLabel         string //SecurityOpts
 	ProcessLabel       string //SecurityOpts
@@ -131,6 +133,7 @@ type CreateConfig struct {
 	SeccompProfilePath string //SecurityOpts
 	SecurityOpts       []string
 	Rootfs             string
+	LocalVolumes       []string //Keeps track of the built-in volumes of container used in the --volumes-from flag
 }
 
 func u32Ptr(i int64) *uint32     { u := uint32(i); return &u }
@@ -215,6 +218,52 @@ func (c *CreateConfig) GetVolumeMounts(specMounts []spec.Mount) ([]spec.Mount, e
 	return m, nil
 }
 
+// GetVolumesFrom reads the create-config artifact of the container to get volumes from
+// and adds it to c.Volumes of the curent container.
+func (c *CreateConfig) GetVolumesFrom() error {
+	var options string
+	for _, vol := range c.VolumesFrom {
+		splitVol := strings.SplitN(vol, ":", 2)
+		if len(splitVol) == 2 {
+			options = splitVol[1]
+		}
+		ctr, err := c.Runtime.LookupContainer(splitVol[0])
+		if err != nil {
+			return errors.Wrapf(err, "error looking up container %q", splitVol[0])
+		}
+		var createArtifact CreateConfig
+		artifact, err := ctr.GetArtifact("create-config")
+		if err != nil {
+			return errors.Wrapf(err, "error getting create-config artifact for %q", splitVol[0])
+		}
+		if err := json.Unmarshal(artifact, &createArtifact); err != nil {
+			return err
+		}
+
+		for key := range createArtifact.BuiltinImgVolumes {
+			c.LocalVolumes = append(c.LocalVolumes, key)
+		}
+
+		for _, i := range createArtifact.Volumes {
+			// Volumes format is host-dir:ctr-dir[:options], so get the host and ctr dir
+			// and add on the options given by the user to the flag.
+			spliti := strings.SplitN(i, ":", 3)
+			// Throw error if mounting volume from container with Z option (private label)
+			// Override this by adding 'z' to options.
+			if len(spliti) > 2 && strings.Contains(spliti[2], "Z") && !strings.Contains(options, "z") {
+				return errors.Errorf("volume mounted with private option 'Z' in %q. Use option 'z' to mount in current container", ctr.ID())
+			}
+			if options == "" {
+				// Mount the volumes with the default options
+				c.Volumes = append(c.Volumes, createArtifact.Volumes...)
+			} else {
+				c.Volumes = append(c.Volumes, spliti[0]+":"+spliti[1]+":"+options)
+			}
+		}
+	}
+	return nil
+}
+
 //GetTmpfsMounts takes user provided input for Tmpfs mounts and creates Mount structs
 func (c *CreateConfig) GetTmpfsMounts() []spec.Mount {
 	var m []spec.Mount
@@ -289,6 +338,10 @@ func (c *CreateConfig) GetContainerCreateOptions(runtime *libpod.Runtime) ([]lib
 		options = append(options, libpod.WithUserVolumes(volumes))
 	}
 
+	if len(c.LocalVolumes) != 0 {
+		options = append(options, libpod.WithLocalVolumes(c.LocalVolumes))
+	}
+
 	if len(c.Command) != 0 {
 		options = append(options, libpod.WithCommand(c.Command))
 	}

pkg/spec/spec.go

@@ -248,6 +248,9 @@ func CreateConfigToOCISpec(config *CreateConfig) (*spec.Spec, error) { //nolint
 	}
 
 	// BIND MOUNTS
+	if err := config.GetVolumesFrom(); err != nil {
+		return nil, errors.Wrap(err, "error getting volume mounts from --volumes-from flag")
+	}
 	mounts, err := config.GetVolumeMounts(configSpec.Mounts)
 	if err != nil {
 		return nil, errors.Wrapf(err, "error getting volume mounts")

test/e2e/run_test.go

@@ -510,4 +510,41 @@ USER mail`
 		session.WaitWithDefaultTimeout()
 		Expect(session.ExitCode()).To(Equal(0))
 	})
+
+	It("podman run --volumes-from flag", func() {
+		vol := filepath.Join(podmanTest.TempDir, "vol-test")
+		err := os.MkdirAll(vol, 0755)
+		Expect(err).To(BeNil())
+
+		volFile := filepath.Join(vol, "test.txt")
+		data := "Testing --volumes-from!!!"
+		err = ioutil.WriteFile(volFile, []byte(data), 0755)
+		Expect(err).To(BeNil())
+
+		session := podmanTest.Podman([]string{"create", "--volume", vol + ":/myvol", "docker.io/library/redis:alpine", "sh"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		ctrID := session.OutputToString()
+
+		session = podmanTest.Podman([]string{"run", "--volumes-from", ctrID, ALPINE, "echo", "'testing read-write!' >> myvol/test.txt"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+
+		session = podmanTest.Podman([]string{"run", "--volumes-from", ctrID + ":z", ALPINE, "ls"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+	})
+
+	It("podman run --volumes-from flag with built-in volumes", func() {
+		session := podmanTest.Podman([]string{"create", "docker.io/library/redis:alpine", "sh"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		ctrID := session.OutputToString()
+
+		session = podmanTest.Podman([]string{"run", "--volumes-from", ctrID, ALPINE, "ls"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		Expect(session.OutputToString()).To(ContainSubstring("data"))
+
+	})
 })