Added option to share kernel namespaces in libpod and podman

A pause container is added to the pod if the user opts in. The default pause image and command can be overridden. Pause containers are ignored in ps unless the -a option is present. Pod inspect and pod ps show shared namespaces and pause container. A pause container can't be removed with podman rm, and a pod can be removed if it only has a pause container.

Signed-off-by: haircommander <pehunt@redhat.com>

Closes: #1187
Approved by: mheon

1 files changed, 60 insertions, 0 deletions

diff --git a/libpod/runtime_pod_pause_linux.go b/libpod/runtime_pod_pause_linux.go
new file mode 100644
index 000000000..41bf8b041
--- /dev/null
+++ b/libpod/runtime_pod_pause_linux.go
@@ -0,0 +1,60 @@
+// +build linux
+
+package libpod
+
+import (
+	"context"
+
+	"github.com/containers/libpod/libpod/image"
+	"github.com/opencontainers/runtime-tools/generate"
+)
+
+const (
+	// IDTruncLength is the length of the pod's id that will be used to make the
+	// pause container name
+	IDTruncLength = 12
+)
+
+func (r *Runtime) makePauseContainer(ctx context.Context, p *Pod, imgName, imgID string) (*Container, error) {
+
+	// Set up generator for pause container defaults
+	g, err := generate.New("linux")
+	if err != nil {
+		return nil, err
+	}
+
+	g.SetRootReadonly(true)
+	g.SetProcessArgs([]string{r.config.PauseCommand})
+
+	containerName := p.ID()[:IDTruncLength] + "-infra"
+	var options []CtrCreateOption
+	options = append(options, r.WithPod(p))
+	options = append(options, WithRootFSFromImage(imgID, imgName, false))
+	options = append(options, WithName(containerName))
+	options = append(options, withIsPause())
+
+	return r.newContainer(ctx, g.Config, options...)
+}
+
+// createPauseContainer wrap creates a pause container for a pod.
+// A pause container becomes the basis for kernel namespace sharing between
+// containers in the pod.
+func (r *Runtime) createPauseContainer(ctx context.Context, p *Pod) (*Container, error) {
+	if !r.valid {
+		return nil, ErrRuntimeStopped
+	}
+
+	newImage, err := r.ImageRuntime().New(ctx, r.config.PauseImage, "", "", nil, nil, image.SigningOptions{}, false, false)
+	if err != nil {
+		return nil, err
+	}
+
+	data, err := newImage.Inspect(ctx)
+	if err != nil {
+		return nil, err
+	}
+	imageName := newImage.Names()[0]
+	imageID := data.ID
+
+	return r.makePauseContainer(ctx, p, imageName, imageID)
+}