Add support for overlay volume mounts in podman.

Add support -v for overlay volume mounts in podman.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

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

cmd/podman/common/specgen.go

@@ -531,12 +531,13 @@ func FillOutSpecGen(s *specgen.SpecGenerator, c *ContainerCLIOpts, args []string
 
 	// Only add read-only tmpfs mounts in case that we are read-only and the
 	// read-only tmpfs flag has been set.
-	mounts, volumes, err := parseVolumes(c.Volume, c.Mount, c.TmpFS, c.ReadOnlyTmpFS && c.ReadOnly)
+	mounts, volumes, overlayVolumes, err := parseVolumes(c.Volume, c.Mount, c.TmpFS, c.ReadOnlyTmpFS && c.ReadOnly)
 	if err != nil {
 		return err
 	}
 	s.Mounts = mounts
 	s.Volumes = volumes
+	s.OverlayVolumes = overlayVolumes
 
 	for _, dev := range c.Devices {
 		s.Devices = append(s.Devices, specs.LinuxDevice{Path: dev})

cmd/podman/common/volumes.go

@@ -34,43 +34,43 @@ var (
 // Does not handle image volumes, init, and --volumes-from flags.
 // Can also add tmpfs mounts from read-only tmpfs.
 // TODO: handle options parsing/processing via containers/storage/pkg/mount
-func parseVolumes(volumeFlag, mountFlag, tmpfsFlag []string, addReadOnlyTmpfs bool) ([]spec.Mount, []*specgen.NamedVolume, error) {
+func parseVolumes(volumeFlag, mountFlag, tmpfsFlag []string, addReadOnlyTmpfs bool) ([]spec.Mount, []*specgen.NamedVolume, []*specgen.OverlayVolume, error) {
 	// Get mounts from the --mounts flag.
 	unifiedMounts, unifiedVolumes, err := getMounts(mountFlag)
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, nil, err
 	}
 
 	// Next --volumes flag.
-	volumeMounts, volumeVolumes, err := getVolumeMounts(volumeFlag)
+	volumeMounts, volumeVolumes, overlayVolumes, err := getVolumeMounts(volumeFlag)
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, nil, err
 	}
 
 	// Next --tmpfs flag.
 	tmpfsMounts, err := getTmpfsMounts(tmpfsFlag)
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, nil, err
 	}
 
 	// Unify mounts from --mount, --volume, --tmpfs.
 	// Start with --volume.
 	for dest, mount := range volumeMounts {
 		if _, ok := unifiedMounts[dest]; ok {
-			return nil, nil, errors.Wrapf(errDuplicateDest, dest)
+			return nil, nil, nil, errors.Wrapf(errDuplicateDest, dest)
 		}
 		unifiedMounts[dest] = mount
 	}
 	for dest, volume := range volumeVolumes {
 		if _, ok := unifiedVolumes[dest]; ok {
-			return nil, nil, errors.Wrapf(errDuplicateDest, dest)
+			return nil, nil, nil, errors.Wrapf(errDuplicateDest, dest)
 		}
 		unifiedVolumes[dest] = volume
 	}
 	// Now --tmpfs
 	for dest, tmpfs := range tmpfsMounts {
 		if _, ok := unifiedMounts[dest]; ok {
-			return nil, nil, errors.Wrapf(errDuplicateDest, dest)
+			return nil, nil, nil, errors.Wrapf(errDuplicateDest, dest)
 		}
 		unifiedMounts[dest] = tmpfs
 	}
@@ -101,15 +101,29 @@ func parseVolumes(volumeFlag, mountFlag, tmpfsFlag []string, addReadOnlyTmpfs bo
 		}
 	}
 
-	// Check for conflicts between named volumes and mounts
+	// Check for conflicts between named volumes, overlay volumes, and mounts
 	for dest := range unifiedMounts {
 		if _, ok := unifiedVolumes[dest]; ok {
-			return nil, nil, errors.Wrapf(errDuplicateDest, "conflict at mount destination %v", dest)
+			return nil, nil, nil, errors.Wrapf(errDuplicateDest, "conflict at mount destination %v", dest)
+		}
+		if _, ok := overlayVolumes[dest]; ok {
+			return nil, nil, nil, errors.Wrapf(errDuplicateDest, "conflict at mount destination %v", dest)
 		}
 	}
 	for dest := range unifiedVolumes {
 		if _, ok := unifiedMounts[dest]; ok {
-			return nil, nil, errors.Wrapf(errDuplicateDest, "conflict at mount destination %v", dest)
+			return nil, nil, nil, errors.Wrapf(errDuplicateDest, "conflict at mount destination %v", dest)
+		}
+		if _, ok := overlayVolumes[dest]; ok {
+			return nil, nil, nil, errors.Wrapf(errDuplicateDest, "conflict at mount destination %v", dest)
+		}
+	}
+	for dest := range overlayVolumes {
+		if _, ok := unifiedMounts[dest]; ok {
+			return nil, nil, nil, errors.Wrapf(errDuplicateDest, "conflict at mount destination %v", dest)
+		}
+		if _, ok := unifiedVolumes[dest]; ok {
+			return nil, nil, nil, errors.Wrapf(errDuplicateDest, "conflict at mount destination %v", dest)
 		}
 	}
 
@@ -119,7 +133,7 @@ func parseVolumes(volumeFlag, mountFlag, tmpfsFlag []string, addReadOnlyTmpfs bo
 		if mount.Type == TypeBind {
 			absSrc, err := filepath.Abs(mount.Source)
 			if err != nil {
-				return nil, nil, errors.Wrapf(err, "error getting absolute path of %s", mount.Source)
+				return nil, nil, nil, errors.Wrapf(err, "error getting absolute path of %s", mount.Source)
 			}
 			mount.Source = absSrc
 		}
@@ -129,8 +143,12 @@ func parseVolumes(volumeFlag, mountFlag, tmpfsFlag []string, addReadOnlyTmpfs bo
 	for _, volume := range unifiedVolumes {
 		finalVolumes = append(finalVolumes, volume)
 	}
+	finalOverlayVolume := make([]*specgen.OverlayVolume, 0)
+	for _, volume := range overlayVolumes {
+		finalOverlayVolume = append(finalOverlayVolume, volume)
+	}
 
-	return finalMounts, finalVolumes, nil
+	return finalMounts, finalVolumes, finalOverlayVolume, nil
 }
 
 // getMounts takes user-provided input from the --mount flag and creates OCI
@@ -465,9 +483,10 @@ func getNamedVolume(args []string) (*specgen.NamedVolume, error) {
 	return newVolume, nil
 }
 
-func getVolumeMounts(volumeFlag []string) (map[string]spec.Mount, map[string]*specgen.NamedVolume, error) {
+func getVolumeMounts(volumeFlag []string) (map[string]spec.Mount, map[string]*specgen.NamedVolume, map[string]*specgen.OverlayVolume, error) {
 	mounts := make(map[string]spec.Mount)
 	volumes := make(map[string]*specgen.NamedVolume)
+	overlayVolumes := make(map[string]*specgen.OverlayVolume)
 
 	volumeFormatErr := errors.Errorf("incorrect volume format, should be [host-dir:]ctr-dir[:option]")
 
@@ -481,7 +500,7 @@ func getVolumeMounts(volumeFlag []string) (map[string]spec.Mount, map[string]*sp
 
 		splitVol := strings.Split(vol, ":")
 		if len(splitVol) > 3 {
-			return nil, nil, errors.Wrapf(volumeFormatErr, vol)
+			return nil, nil, nil, errors.Wrapf(volumeFormatErr, vol)
 		}
 
 		src = splitVol[0]
@@ -496,24 +515,43 @@ func getVolumeMounts(volumeFlag []string) (map[string]spec.Mount, map[string]*sp
 		}
 		if len(splitVol) > 2 {
 			if options, err = parse.ValidateVolumeOpts(strings.Split(splitVol[2], ",")); err != nil {
-				return nil, nil, err
+				return nil, nil, nil, err
 			}
 		}
 
 		// Do not check source dir for anonymous volumes
 		if len(splitVol) > 1 {
 			if err := parse.ValidateVolumeHostDir(src); err != nil {
-				return nil, nil, err
+				return nil, nil, nil, err
 			}
 		}
 		if err := parse.ValidateVolumeCtrDir(dest); err != nil {
-			return nil, nil, err
+			return nil, nil, nil, err
 		}
 
 		cleanDest := filepath.Clean(dest)
 
 		if strings.HasPrefix(src, "/") || strings.HasPrefix(src, ".") {
 			// This is not a named volume
+			overlayFlag := false
+			for _, o := range options {
+				if o == "O" {
+					overlayFlag = true
+					if len(options) > 1 {
+						return nil, nil, nil, errors.New("can't use 'O' with other options")
+					}
+				}
+			}
+			if overlayFlag {
+				// This is a overlay volume
+				newOverlayVol := new(specgen.OverlayVolume)
+				newOverlayVol.Destination = cleanDest
+				newOverlayVol.Source = src
+				if _, ok := overlayVolumes[newOverlayVol.Destination]; ok {
+					return nil, nil, nil, errors.Wrapf(errDuplicateDest, newOverlayVol.Destination)
+				}
+				overlayVolumes[newOverlayVol.Destination] = newOverlayVol
+			} else {
 				newMount := spec.Mount{
 					Destination: cleanDest,
 					Type:        string(TypeBind),
@@ -521,9 +559,10 @@ func getVolumeMounts(volumeFlag []string) (map[string]spec.Mount, map[string]*sp
 					Options:     options,
 				}
 				if _, ok := mounts[newMount.Destination]; ok {
-				return nil, nil, errors.Wrapf(errDuplicateDest, newMount.Destination)
+					return nil, nil, nil, errors.Wrapf(errDuplicateDest, newMount.Destination)
 				}
 				mounts[newMount.Destination] = newMount
+			}
 		} else {
 			// This is a named volume
 			newNamedVol := new(specgen.NamedVolume)
@@ -532,7 +571,7 @@ func getVolumeMounts(volumeFlag []string) (map[string]spec.Mount, map[string]*sp
 			newNamedVol.Options = options
 
 			if _, ok := volumes[newNamedVol.Dest]; ok {
-				return nil, nil, errors.Wrapf(errDuplicateDest, newNamedVol.Dest)
+				return nil, nil, nil, errors.Wrapf(errDuplicateDest, newNamedVol.Dest)
 			}
 			volumes[newNamedVol.Dest] = newNamedVol
 		}
@@ -540,7 +579,7 @@ func getVolumeMounts(volumeFlag []string) (map[string]spec.Mount, map[string]*sp
 		logrus.Debugf("User mount %s:%s options %v", src, dest, options)
 	}
 
-	return mounts, volumes, nil
+	return mounts, volumes, overlayVolumes, nil
 }
 
 // GetTmpfsMounts creates spec.Mount structs for user-requested tmpfs mounts

docs/source/markdown/podman-create.1.md

@@ -811,7 +811,7 @@ Create a tmpfs mount
 
 Mount a temporary filesystem (`tmpfs`) mount into a container, for example:
 
-$ podman run -d --tmpfs /tmp:rw,size=787448k,mode=1777 my_image
+$ podman create -d --tmpfs /tmp:rw,size=787448k,mode=1777 my_image
 
 This command mounts a `tmpfs` at `/tmp` within the container.  The supported mount
 options are the same as the Linux default `mount` flags. If you do not specify
@@ -887,15 +887,20 @@ Set the UTS mode for the container
 
 Create a bind mount. If you specify, ` -v /HOST-DIR:/CONTAINER-DIR`, podman
 bind mounts `/HOST-DIR` in the host to `/CONTAINER-DIR` in the podman
-container. The `OPTIONS` are a comma delimited list and can be: <sup>[[1]](#Footnote1)</sup>
+container.  Similarly, `-v SOURCE-VOLUME:/CONTAINER-DIR` will mount the volume
+in the host to the container. If no such named volume exists, Podman will
+create one. The `OPTIONS` are a comma delimited list and can be: <sup>[[1]](#Footnote1)</sup>
 
-* [rw|ro]
-* [z|Z]
-* [`[r]shared`|`[r]slave`|`[r]private`]
-* [`[r]bind`]
-* [`noexec`|`exec`]
-* [`nodev`|`dev`]
-* [`nosuid`|`suid`]
+The _options_ is a comma delimited list and can be:
+
+* **rw**|**ro**
+* **z**|**Z**
+* [**r**]**shared**|[**r**]**slave**|[**r**]**private**
+* [**r**]**bind**
+* [**no**]**exec**
+* [**no**]**dev**
+* [**no**]**suid**
+* [**O**]
 
 The `CONTAINER-DIR` must be an absolute path such as `/src/docs`. The volume
 will be mounted into the container at this directory.
@@ -908,18 +913,22 @@ the container is removed via the `--rm` flag or `podman rm --volumes`.
 If a volume source is specified, it must be a path on the host or the name of a
 named volume. Host paths are allowed to be absolute or relative; relative paths
 are resolved relative to the directory Podman is run in. Any source that does
-not begin with a `.` or `/` it will be treated as the name of a named volume.
+not begin with a `.` or `/` will be treated as the name of a named volume.
 If a volume with that name does not exist, it will be created. Volumes created
-with names are not anonymous and are not removed by `--rm` and
-`podman rm --volumes`.
+with names are not anonymous. They are not removed by the `--rm` option and the
+`podman rm --volumes` command.
 
 You can specify multiple  **-v** options to mount one or more volumes into a
 container.
 
+  `Write Protected Volume Mounts`
+
 You can add `:ro` or `:rw` suffix to a volume to mount it read-only or
 read-write mode, respectively. By default, the volumes are mounted read-write.
 See examples.
 
+  `Labeling Volume Mounts`
+
 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
@@ -933,6 +942,37 @@ content label. Shared volume labels allow all containers to read/write content.
 The `Z` option tells Podman to label the content with a private unshared label.
 Only the current container can use a private volume.
 
+  `Overlay Volume Mounts`
+
+   The `:O` flag tells Podman to mount the directory from the host as a
+temporary storage using the `overlay file system`. The container processes
+can modify content within the mountpoint which is stored in the
+container storage in a separate directory.  In overlay terms, the source
+directory will be the lower, and the container storage directory will be the
+upper. Modifications to the mount point are destroyed when the container
+finishes executing, similar to a tmpfs mount point being unmounted.
+
+  Subsequent executions of the container will see the original source directory
+content, any changes from previous container executions no longer exists.
+
+  One use case of the overlay mount is sharing the package cache from the
+host into the container to allow speeding up builds.
+
+  Note:
+
+     - The `O` flag conflicts with other options listed above.
+Content mounted into the container is labeled with the private label.
+       On SELinux systems, labels in the source directory must be readable
+by the container label. Usually containers can read/execute `container_share_t`
+and can read/write `container_file_t`. If you can not change the labels on a
+source volume, SELinux container separation must be disabled for the container
+to work.
+     - The source directory mounted into the container with an overlay mount
+should not be modified, it can cause unexpected failures.  It is recommended
+that you do not modify the directory until the container finishes running.
+
+  `Mounts propagation`
+
 By default bind mounted volumes are `private`. That means any mounts done
 inside container will not be visible on host and vice versa. One can change
 this behavior by specifying a volume mount propagation property. Making a
@@ -1110,7 +1150,7 @@ b
 NOTE: Use the environment variable `TMPDIR` to change the temporary storage location of downloaded container images. Podman defaults to use `/var/tmp`.
 
 ## SEE ALSO
-subgid(5), subuid(5), libpod.conf(5), systemd.unit(5), setsebool(8), slirp4netns(1), fuse-overlayfs(1)
+**subgid**(5), **subuid**(5), **libpod.conf**(5), **systemd.unit**(5), **setsebool**(8), **slirp4netns**(1), **fuse-overlayfs**(1).
 
 ## HISTORY
 October 2017, converted from Docker documentation to Podman by Dan Walsh for Podman <dwalsh@redhat.com>

docs/source/markdown/podman-run.1.md

@@ -936,6 +936,7 @@ The _options_ is a comma delimited list and can be: <sup>[[1]](#Footnote1)</sup>
 * [**no**]**exec**
 * [**no**]**dev**
 * [**no**]**suid**
+* [**O**]
 
 The _container-dir_ must be an absolute path.
 
@@ -947,7 +948,7 @@ the container is removed via the **--rm** flag or **podman rm --volumes**.
 If a volume source is specified, it must be a path on the host or the name of a
 named volume. Host paths are allowed to be absolute or relative; relative paths
 are resolved relative to the directory Podman is run in. Any source that does
-not begin with a **.** or **/** it will be treated as the name of a named volume.
+not begin with a **.** or **/** will be treated as the name of a named volume.
 If a volume with that name does not exist, it will be created. Volumes created
 with names are not anonymous and are not removed by **--rm** and
 **podman rm --volumes**.
@@ -958,6 +959,8 @@ container.
 You can add **:ro** or **:rw** option to mount a volume in read-only or
 read-write mode, respectively. By default, the volumes are mounted read-write.
 
+  `Labeling Volume Mounts`
+
 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
@@ -969,9 +972,41 @@ 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.
 The **Z** option tells Podman to label the content with a private unshared label.
+
+  `Overlay Volume Mounts`
+
+   The `:O` flag tells Podman to mount the directory from the host as a
+temporary storage using the `overlay file system`. The container processes
+can modify content within the mountpoint which is stored in the
+container storage in a separate directory.  In overlay terms, the source
+directory will be the lower, and the container storage directory will be the
+upper. Modifications to the mount point are destroyed when the container
+finishes executing, similar to a tmpfs mount point being unmounted.
+
+  Subsequent executions of the container will see the original source directory
+content, any changes from previous container executions no longer exists.
+
+  One use case of the overlay mount is sharing the package cache from the
+host into the container to allow speeding up builds.
+
+  Note:
+
+     - The `O` flag conflicts with other options listed above.
+Content mounted into the container is labeled with the private label.
+       On SELinux systems, labels in the source directory must be readable
+by the container label. Usually containers can read/execute `container_share_t`
+and can read/write `container_file_t`. If you can not change the labels on a
+source volume, SELinux container separation must be disabled for the container
+to work.
+     - The source directory mounted into the container with an overlay mount
+should not be modified, it can cause unexpected failures.  It is recommended
+that you do not modify the directory until the container finishes running.
+
 Only the current container can use a private volume.
 
-By default bind mounted volumes are **private**. That means any mounts done
+  `Mounts propagation`
+
+By default bind mounted volumes are `private`. That means any mounts done
 inside container will not be visible on host and vice versa. One can change
 this behavior by specifying a volume mount propagation property. Making a
 volume shared mounts done under that volume inside container will be
@@ -1228,6 +1263,8 @@ considered as an orphan and wiped if you execute **podman volume prune**:
 $ podman run -v /var/db:/data1 -i -t fedora bash
 
 $ podman run -v data:/data2 -i -t fedora bash
+
+$ podman run -v /var/cache/dnf:/var/cache/dnf:O -ti fedora dnf -y update
 ```
 
 Using **--mount** flags to mount a host directory as a container folder, specify
@@ -1398,8 +1435,6 @@ October 2017, converted from Docker documentation to Podman by Dan Walsh for Pod
 
 November 2015, updated by Sally O'Malley <somalley@redhat.com>
 
-July 2014, updated by Sven Dowideit <SvenDowideit@home.org.au>
-
 June 2014, updated by Sven Dowideit <SvenDowideit@home.org.au>
 
 April 2014, Originally compiled by William Henry <whenry@redhat.com> based on docker.com source material and internal work.

libpod/container.go

@@ -262,6 +262,8 @@ type ContainerConfig struct {
 	Mounts []string `json:"mounts,omitempty"`
 	// NamedVolumes lists the named volumes to mount into the container.
 	NamedVolumes []*ContainerNamedVolume `json:"namedVolumes,omitempty"`
+	// OverlayVolumes lists the overlay volumes to mount into the container.
+	OverlayVolumes []*ContainerOverlayVolume `json:"overlayVolumes,omitempty"`
 
 	// Security Config
 
@@ -449,6 +451,15 @@ type ContainerNamedVolume struct {
 	Options []string `json:"options,omitempty"`
 }
 
+// ContainerOverlayVolume is a overlay volume that will be mounted into the
+// container. Each volume is a libpod Volume present in the state.
+type ContainerOverlayVolume struct {
+	// Destination is the absolute path where the mount will be placed in the container.
+	Dest string `json:"dest"`
+	// Source specifies the source path of the mount.
+	Source string `json:"source,omitempty"`
+}
+
 // Config accessors
 // Unlocked
 

libpod/container_internal.go

@@ -1588,6 +1588,12 @@ func (c *Container) cleanupStorage() error {
 		}
 	}
 
+	if err := c.cleanupOverlayMounts(); err != nil {
+		// If the container can't remove content report the error
+		logrus.Errorf("Failed to cleanup overlay mounts for %s: %v", c.ID(), err)
+		cleanupErr = err
+	}
+
 	if c.config.Rootfs != "" {
 		return cleanupErr
 	}

libpod/container_internal_linux.go

@@ -20,6 +20,7 @@ import (
 
 	cnitypes "github.com/containernetworking/cni/pkg/types/current"
 	"github.com/containernetworking/plugins/pkg/ns"
+	"github.com/containers/buildah/pkg/overlay"
 	"github.com/containers/buildah/pkg/secrets"
 	"github.com/containers/common/pkg/apparmor"
 	"github.com/containers/common/pkg/config"
@@ -319,6 +320,19 @@ func (c *Container) generateSpec(ctx context.Context) (*spec.Spec, error) {
 		}
 	}
 
+	// Add overlay volumes
+	for _, overlayVol := range c.config.OverlayVolumes {
+		contentDir, err := overlay.TempDir(c.config.StaticDir, c.RootUID(), c.RootGID())
+		if err != nil {
+			return nil, errors.Wrapf(err, "failed to create TempDir in the %s directory", c.config.StaticDir)
+		}
+		overlayMount, err := overlay.Mount(contentDir, overlayVol.Source, overlayVol.Dest, c.RootUID(), c.RootGID(), c.runtime.store.GraphOptions())
+		if err != nil {
+			return nil, errors.Wrapf(err, "creating overlay failed %q", overlayVol.Source)
+		}
+		g.AddMount(overlayMount)
+	}
+
 	hasHomeSet := false
 	for _, s := range c.config.Spec.Process.Env {
 		if strings.HasPrefix(s, "HOME=") {
@@ -1642,3 +1656,7 @@ func (c *Container) copyTimezoneFile(zonePath string) (string, error) {
 	}
 	return localtimeCopy, err
 }
+
+func (c *Container) cleanupOverlayMounts() error {
+	return overlay.CleanupContent(c.config.StaticDir)
+}

libpod/container_internal_unsupported.go

@@ -46,6 +46,10 @@ func (c *Container) getOCICgroupPath() (string, error) {
 	return "", define.ErrNotImplemented
 }
 
+func (c *Container) cleanupOverlayMounts() error {
+	return nil
+}
+
 func (c *Container) getUserOverrides() *lookup.Overrides {
 	return nil
 }

libpod/container_validate.go

@@ -99,5 +99,24 @@ func (c *Container) validate() error {
 		return errors.Wrapf(define.ErrInvalidArg, "cannot add to /etc/hosts if using image's /etc/hosts")
 	}
 
+	// Check named volume and overlay volumes destination conflits
+	destinations := make(map[string]bool)
+	for _, vol := range c.config.NamedVolumes {
+		// Don't check if they already exist.
+		// If they don't we will automatically create them.
+		if _, ok := destinations[vol.Dest]; ok {
+			return errors.Wrapf(define.ErrInvalidArg, "two volumes found with destination %s", vol.Dest)
+		}
+		destinations[vol.Dest] = true
+	}
+	for _, vol := range c.config.OverlayVolumes {
+		// Don't check if they already exist.
+		// If they don't we will automatically create them.
+		if _, ok := destinations[vol.Dest]; ok {
+			return errors.Wrapf(define.ErrInvalidArg, "two volumes found with destination %s", vol.Dest)
+		}
+		destinations[vol.Dest] = true
+	}
+
 	return nil
 }

libpod/options.go

@@ -1380,17 +1380,7 @@ func WithNamedVolumes(volumes []*ContainerNamedVolume) CtrCreateOption {
 			return define.ErrCtrFinalized
 		}
 
-		destinations := make(map[string]bool)
-
 		for _, vol := range volumes {
-			// Don't check if they already exist.
-			// If they don't we will automatically create them.
-
-			if _, ok := destinations[vol.Dest]; ok {
-				return errors.Wrapf(define.ErrInvalidArg, "two volumes found with destination %s", vol.Dest)
-			}
-			destinations[vol.Dest] = true
-
 			mountOpts, err := util.ProcessOptions(vol.Options, false, "")
 			if err != nil {
 				return errors.Wrapf(err, "error processing options for named volume %q mounted at %q", vol.Name, vol.Dest)
@@ -1407,6 +1397,25 @@ func WithNamedVolumes(volumes []*ContainerNamedVolume) CtrCreateOption {
 	}
 }
 
+// WithOverlayVolumes adds the given overlay volumes to the container.
+func WithOverlayVolumes(volumes []*ContainerOverlayVolume) CtrCreateOption {
+	return func(ctr *Container) error {
+		if ctr.valid {
+			return define.ErrCtrFinalized
+		}
+
+		for _, vol := range volumes {
+
+			ctr.config.OverlayVolumes = append(ctr.config.OverlayVolumes, &ContainerOverlayVolume{
+				Dest:   vol.Dest,
+				Source: vol.Source,
+			})
+		}
+
+		return nil
+	}
+}
+
 // WithHealthCheck adds the healthcheck to the container config
 func WithHealthCheck(healthCheck *manifest.Schema2HealthConfig) CtrCreateOption {
 	return func(ctr *Container) error {

libpod/runtime.go

@@ -577,7 +577,7 @@ func (r *Runtime) Shutdown(force bool) error {
 	}
 
 	var lastError error
-	// If no store was requested, it can bew nil and there is no need to
+	// If no store was requested, it can be nil and there is no need to
 	// attempt to shut it down
 	if r.store != nil {
 		if _, err := r.store.Shutdown(force); err != nil {

pkg/specgen/generate/container_create.go

@@ -201,6 +201,9 @@ func createContainerOptions(ctx context.Context, rt *libpod.Runtime, s *specgen.
 	for _, volume := range volumes {
 		destinations = append(destinations, volume.Dest)
 	}
+	for _, overlayVolume := range s.OverlayVolumes {
+		destinations = append(destinations, overlayVolume.Destination)
+	}
 	options = append(options, libpod.WithUserVolumes(destinations))
 
 	if len(volumes) != 0 {
@@ -215,6 +218,17 @@ func createContainerOptions(ctx context.Context, rt *libpod.Runtime, s *specgen.
 		options = append(options, libpod.WithNamedVolumes(vols))
 	}
 
+	if len(s.OverlayVolumes) != 0 {
+		var vols []*libpod.ContainerOverlayVolume
+		for _, v := range s.OverlayVolumes {
+			vols = append(vols, &libpod.ContainerOverlayVolume{
+				Dest:   v.Destination,
+				Source: v.Source,
+			})
+		}
+		options = append(options, libpod.WithOverlayVolumes(vols))
+	}
+
 	if s.Command != nil {
 		options = append(options, libpod.WithCommand(s.Command))
 	}

pkg/specgen/specgen.go

@@ -198,6 +198,9 @@ type ContainerStorageConfig struct {
 	// there are conflicts.
 	// Optional.
 	Volumes []*NamedVolume `json:"volumes,omitempty"`
+	// Overlay volumes are named volumes that will be added to the container.
+	// Optional.
+	OverlayVolumes []*OverlayVolume `json:"overlay_volumes,omitempty"`
 	// Devices are devices that will be added to the container.
 	// Optional.
 	Devices []spec.LinuxDevice `json:"devices,omitempty"`
@@ -443,6 +446,15 @@ type NamedVolume struct {
 	Options []string
 }
 
+// OverlayVolume holds information about a overlay volume that will be mounted into
+// the container.
+type OverlayVolume struct {
+	// Destination is the absolute path where the mount will be placed in the container.
+	Destination string `json:"destination"`
+	// Source specifies the source path of the mount.
+	Source string `json:"source,omitempty"`
+}
+
 // PortMapping is one or more ports that will be mapped into the container.
 type PortMapping struct {
 	// HostIP is the IP that we will bind to on the host.

pkg/util/mountOpts.go

@@ -33,6 +33,10 @@ func ProcessOptions(options []string, isTmpfs bool, sourcePath string) ([]string
 		// Some options have parameters - size, mode
 		splitOpt := strings.SplitN(opt, "=", 2)
 		switch splitOpt[0] {
+		case "O":
+			if len(options) > 1 {
+				return nil, errors.Wrapf(ErrDupeMntOption, "'O' option can not be used with other options")
+			}
 		case "exec", "noexec":
 			if foundExec {
 				return nil, errors.Wrapf(ErrDupeMntOption, "only one of 'noexec' and 'exec' can be used")

test/e2e/run_volume_test.go

@@ -9,6 +9,7 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/containers/libpod/v2/pkg/rootless"
 	. "github.com/containers/libpod/v2/test/utils"
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
@@ -450,4 +451,92 @@ VOLUME /test/`
 		Expect(data[0].Mounts[0].Source).To(Equal("/tmp"))
 		Expect(data[0].Mounts[0].Destination).To(Equal("/test"))
 	})
+
+	It("podman run with overlay volume flag", func() {
+		if os.Getenv("container") != "" {
+			Skip("Overlay mounts not supported when running in a container")
+		}
+		if rootless.IsRootless() {
+			if _, err := exec.LookPath("fuse_overlay"); err != nil {
+				Skip("Fuse-Overlayfs required for rootless overlay mount test")
+			}
+		}
+		mountPath := filepath.Join(podmanTest.TempDir, "secrets")
+		os.Mkdir(mountPath, 0755)
+		testFile := filepath.Join(mountPath, "test1")
+		f, err := os.Create(testFile)
+		f.Close()
+
+		// Make sure host directory gets mounted in to container as overlay
+		session := podmanTest.Podman([]string{"run", "--rm", "-v", fmt.Sprintf("%s:/run/test:O", mountPath), ALPINE, "grep", "/run/test", "/proc/self/mountinfo"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		found, matches := session.GrepString("/run/test")
+		Expect(found).Should(BeTrue())
+		Expect(matches[0]).To(ContainSubstring("overlay"))
+
+		// Make sure host files show up in the container
+		session = podmanTest.Podman([]string{"run", "--rm", "-v", fmt.Sprintf("%s:/run/test:O", mountPath), ALPINE, "ls", "/run/test/test1"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+
+		// Make sure modifications in container do not show up on host
+		session = podmanTest.Podman([]string{"run", "--rm", "-v", fmt.Sprintf("%s:/run/test:O", mountPath), ALPINE, "touch", "/run/test/container"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		_, err = os.Stat(filepath.Join(mountPath, "container"))
+		Expect(err).To(Not(BeNil()))
+
+		// Make sure modifications in container disappear when container is stopped
+		session = podmanTest.Podman([]string{"create", "-d", "-v", fmt.Sprintf("%s:/run/test:O", mountPath), ALPINE, "top"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		session = podmanTest.Podman([]string{"start", "-l"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		session = podmanTest.Podman([]string{"exec", "-l", "touch", "/run/test/container"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		session = podmanTest.Podman([]string{"exec", "-l", "ls", "/run/test/container"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		session = podmanTest.Podman([]string{"stop", "-l"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		session = podmanTest.Podman([]string{"start", "-l"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+		session = podmanTest.Podman([]string{"exec", "-l", "ls", "/run/test/container"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Not(Equal(0)))
+	})
+
+	It("overlay volume conflicts with named volume and mounts", func() {
+		mountPath := filepath.Join(podmanTest.TempDir, "secrets")
+		os.Mkdir(mountPath, 0755)
+		testFile := filepath.Join(mountPath, "test1")
+		f, err := os.Create(testFile)
+		Expect(err).To(BeNil())
+		f.Close()
+		mountSrc := filepath.Join(podmanTest.TempDir, "vol-test1")
+		err = os.MkdirAll(mountSrc, 0755)
+		Expect(err).To(BeNil())
+		mountDest := "/run/test"
+		volName := "myvol"
+
+		session := podmanTest.Podman([]string{"volume", "create", volName})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+
+		// overlay and named volume destinations conflict
+		session = podmanTest.Podman([]string{"run", "--rm", "-v", fmt.Sprintf("%s:%s:O", mountPath, mountDest), "-v", fmt.Sprintf("%s:%s", volName, mountDest), ALPINE})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Not(Equal(0)))
+		// overlay and bind mount destinations conflict
+		session = podmanTest.Podman([]string{"run", "--rm", "-v", fmt.Sprintf("%s:%s:O", mountPath, mountDest), "--mount", fmt.Sprintf("type=bind,src=%s,target=%s", mountSrc, mountDest), ALPINE})
+		Expect(session.ExitCode()).To(Not(Equal(0)))
+		// overlay and tmpfs mount destinations conflict
+		session = podmanTest.Podman([]string{"run", "--rm", "-v", fmt.Sprintf("%s:%s:O", mountPath, mountDest), "--mount", fmt.Sprintf("type=tmpfs,target=%s", mountDest), ALPINE})
+		Expect(session.ExitCode()).To(Not(Equal(0)))
+	})
 })