container: allow clone to an existing pod

Closes: https://github.com/containers/podman/issues/3979

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

cmd/podman/common/create.go

@@ -394,14 +394,6 @@ func DefineCreateFlags(cmd *cobra.Command, cf *entities.ContainerCreateOptions,
 		)
 		_ = cmd.RegisterFlagCompletionFunc(platformFlagName, completion.AutocompleteNone)
 
-		podFlagName := "pod"
-		createFlags.StringVar(
-			&cf.Pod,
-			podFlagName, "",
-			"Run container in an existing pod",
-		)
-		_ = cmd.RegisterFlagCompletionFunc(podFlagName, AutocompletePods)
-
 		podIDFileFlagName := "pod-id-file"
 		createFlags.StringVar(
 			&cf.PodIDFile,
@@ -837,6 +829,14 @@ func DefineCreateFlags(cmd *cobra.Command, cf *entities.ContainerCreateOptions,
 		)
 		_ = cmd.RegisterFlagCompletionFunc(nameFlagName, completion.AutocompleteNone)
 
+		podFlagName := "pod"
+		createFlags.StringVar(
+			&cf.Pod,
+			podFlagName, "",
+			"Run container in an existing pod",
+		)
+		_ = cmd.RegisterFlagCompletionFunc(podFlagName, AutocompletePods)
+
 		cpuPeriodFlagName := "cpu-period"
 		createFlags.Uint64Var(
 			&cf.CPUPeriod,

docs/source/markdown/podman-container-clone.1.md

@@ -141,6 +141,12 @@ If no memory limits are specified, the original container's will be used.
 
 Set a custom name for the cloned container. The default if not specified is of the syntax: **<ORIGINAL_NAME>-clone**
 
+#### **--pod**=*name*
+
+Clone the container in an existing pod.  It is helpful to move a container to an
+existing pod.  The container will join the pod shared namespaces, losing its configuration
+that conflicts with the shared namespaces.
+
 #### **--run**
 
 When set to true, this flag runs the newly created container after the

pkg/domain/infra/abi/containers.go

@@ -1496,6 +1496,35 @@ func (ic *ContainerEngine) ContainerClone(ctx context.Context, ctrCloneOpts enti
 		return nil, err
 	}
 
+	if ctrCloneOpts.CreateOpts.Pod != "" {
+		pod, err := ic.Libpod.LookupPod(ctrCloneOpts.CreateOpts.Pod)
+		if err != nil {
+			return nil, err
+		}
+
+		allNamespaces := []struct {
+			isShared bool
+			value    *specgen.Namespace
+		}{
+			{pod.SharesPID(), &spec.PidNS},
+			{pod.SharesNet(), &spec.NetNS},
+			{pod.SharesCgroup(), &spec.CgroupNS},
+			{pod.SharesIPC(), &spec.IpcNS},
+			{pod.SharesUTS(), &spec.UtsNS},
+		}
+
+		printWarning := false
+		for _, n := range allNamespaces {
+			if n.isShared && !n.value.IsDefault() {
+				*n.value = specgen.Namespace{NSMode: specgen.Default}
+				printWarning = true
+			}
+		}
+		if printWarning {
+			logrus.Warning("At least one namespace was reset to the default configuration")
+		}
+	}
+
 	err = specgenutil.FillOutSpecGen(spec, &ctrCloneOpts.CreateOpts, []string{})
 	if err != nil {
 		return nil, err

test/e2e/container_clone_test.go

@@ -184,4 +184,41 @@ var _ = Describe("Podman container clone", func() {
 		Expect(ctrInspect.InspectContainerToJSON()[0].HostConfig.NetworkMode).Should(Equal(runInspect.InspectContainerToJSON()[0].HostConfig.NetworkMode))
 	})
 
+	It("podman container clone to a pod", func() {
+		createPod := podmanTest.Podman([]string{"pod", "create", "--share", "uts", "--name", "foo-pod"})
+		createPod.WaitWithDefaultTimeout()
+		Expect(createPod).To(Exit(0))
+
+		ctr := podmanTest.RunTopContainer("ctr")
+		ctr.WaitWithDefaultTimeout()
+		Expect(ctr).Should(Exit(0))
+
+		clone := podmanTest.Podman([]string{"container", "clone", "--name", "cloned", "--pod", "foo-pod", "ctr"})
+		clone.WaitWithDefaultTimeout()
+		Expect(clone).To(Exit(0))
+
+		ctrInspect := podmanTest.Podman([]string{"inspect", "cloned"})
+		ctrInspect.WaitWithDefaultTimeout()
+		Expect(ctrInspect).Should(Exit(0))
+
+		Expect(ctrInspect.InspectContainerToJSON()[0].Pod).Should(Equal(createPod.OutputToString()))
+
+		Expect(ctrInspect.InspectContainerToJSON()[0].HostConfig.NetworkMode).Should(Not(ContainSubstring("container:")))
+
+		createPod = podmanTest.Podman([]string{"pod", "create", "--share", "uts,net", "--name", "bar-pod"})
+		createPod.WaitWithDefaultTimeout()
+		Expect(createPod).To(Exit(0))
+
+		clone = podmanTest.Podman([]string{"container", "clone", "--name", "cloned2", "--pod", "bar-pod", "ctr"})
+		clone.WaitWithDefaultTimeout()
+		Expect(clone).To(Exit(0))
+
+		ctrInspect = podmanTest.Podman([]string{"inspect", "cloned2"})
+		ctrInspect.WaitWithDefaultTimeout()
+		Expect(ctrInspect).Should(Exit(0))
+
+		Expect(ctrInspect.InspectContainerToJSON()[0].Pod).Should(Equal(createPod.OutputToString()))
+
+		Expect(ctrInspect.InspectContainerToJSON()[0].HostConfig.NetworkMode).Should(ContainSubstring("container:"))
+	})
 })