Implement podman run option --cgroup-parent

Example:

sudo /usr/local/bin/podman run --cgroup-parent=/zzz fedora cat /proc/self/cgroup

Signed-off-by: Jhon Honce <jhonce@redhat.com>

Closes: #370
Approved by: rhatdan

3 files changed, 4 insertions, 3 deletions

diff --git a/libpod/container.go b/libpod/container.go
index d3a58d904..469b4180d 100644
--- a/libpod/container.go
+++ b/libpod/container.go
@@ -38,7 +38,7 @@ const (
 )
 
 // CgroupParent is the default prefix to a cgroup path in libpod
-var CgroupParent = "/libpod_parent"
+var DefaultCgroupParent = "/libpod_parent"
 
 // LinuxNS represents a Linux namespace
 type LinuxNS int
diff --git a/libpod/container_internal.go b/libpod/container_internal.go
index 858cf3cbe..6e9852d1e 100644
--- a/libpod/container_internal.go
+++ b/libpod/container_internal.go
@@ -146,7 +146,7 @@ func newContainer(rspec *spec.Spec, lockDir string) (*Container, error) {
 	ctr.config.CreatedTime = time.Now()
 
 	ctr.config.ShmSize = DefaultShmSize
-	ctr.config.CgroupParent = CgroupParent
+	ctr.config.CgroupParent = DefaultCgroupParent
 
 	// Path our lock file will reside at
 	lockPath := filepath.Join(lockDir, ctr.config.ID)
diff --git a/libpod/options.go b/libpod/options.go
index 56e8fa203..6d3091378 100644
--- a/libpod/options.go
+++ b/libpod/options.go
@@ -656,6 +656,7 @@ func WithLogPath(path string) CtrCreateOption {
 }
 
 // WithCgroupParent sets the Cgroup Parent of the new container
+// Default used if not overridden on command line
 func WithCgroupParent(parent string) CtrCreateOption {
 	return func(ctr *Container) error {
 		if ctr.valid {
@@ -663,7 +664,7 @@ func WithCgroupParent(parent string) CtrCreateOption {
 		}
 
 		if parent == "" {
-			return errors.Wrapf(ErrInvalidArg, "cgroup parent cannot be empty")
+			return nil
 		}
 
 		ctr.config.CgroupParent = parent