Disable checkpointing of containers started with --rm

Trying to checkpoint a container started with --rm works, but it makes
no sense as the container, including the checkpoint, will be deleted
after writing the checkpoint. This commit inhibits checkpointing
containers started with '--rm' unless '--export' is used. If the
checkpoint is exported it can easily be restored from the exported
checkpoint, even if '--rm' is used. To restore a container from a
checkpoint it is even necessary to manually run 'podman rm' if the
container is not started with '--rm'.

Signed-off-by: Adrian Reber <areber@redhat.com>

libpod/container_internal_linux.go

@@ -676,6 +676,10 @@ func (c *Container) checkpoint(ctx context.Context, options ContainerCheckpointO
 		return errors.Wrapf(define.ErrCtrStateInvalid, "%q is not running, cannot checkpoint", c.state.State)
 	}
 
+	if c.AutoRemove() && options.TargetFile == "" {
+		return errors.Errorf("Cannot checkpoint containers that have been started with '--rm' unless '--export' is used")
+	}
+
 	if err := c.checkpointRestoreLabelLog("dump.log"); err != nil {
 		return err
 	}

test/e2e/checkpoint_test.go

@@ -588,4 +588,47 @@ var _ = Describe("Podman checkpoint", func() {
 		// Remove exported checkpoint
 		os.Remove(fileName)
 	})
+
+	It("podman checkpoint a container started with --rm", func() {
+		// Start the container
+		localRunString := getRunString([]string{"--rm", ALPINE, "top"})
+		session := podmanTest.Podman(localRunString)
+		session.WaitWithDefaultTimeout()
+		cid := session.OutputToString()
+		Expect(podmanTest.NumberOfContainersRunning()).To(Equal(1))
+
+		// Checkpoint the container - this should fail as it was started with --rm
+		result := podmanTest.Podman([]string{"container", "checkpoint", "-l"})
+		result.WaitWithDefaultTimeout()
+		Expect(result).To(ExitWithError())
+		Expect(result.ErrorToString()).To(ContainSubstring("Cannot checkpoint containers that have been started with '--rm'"))
+
+		// Checkpointing with --export should still work
+		fileName := "/tmp/checkpoint-" + cid + ".tar.gz"
+
+		result = podmanTest.Podman([]string{"container", "checkpoint", "-l", "-e", fileName})
+		result.WaitWithDefaultTimeout()
+
+		// As the container has been started with '--rm' it will be completely
+		// cleaned up after checkpointing.
+		Expect(result.ExitCode()).To(Equal(0))
+		Expect(podmanTest.NumberOfContainersRunning()).To(Equal(0))
+		Expect(podmanTest.NumberOfContainers()).To(Equal(0))
+
+		result = podmanTest.Podman([]string{"container", "restore", "-i", fileName})
+		result.WaitWithDefaultTimeout()
+
+		Expect(result.ExitCode()).To(Equal(0))
+		Expect(podmanTest.NumberOfContainersRunning()).To(Equal(1))
+		Expect(podmanTest.GetContainerStatus()).To(ContainSubstring("Up"))
+
+		result = podmanTest.Podman([]string{"rm", "-fa"})
+		result.WaitWithDefaultTimeout()
+		Expect(result.ExitCode()).To(Equal(0))
+		Expect(podmanTest.NumberOfContainersRunning()).To(Equal(0))
+		Expect(podmanTest.NumberOfContainers()).To(Equal(0))
+
+		// Remove exported checkpoint
+		os.Remove(fileName)
+	})
 })