implement init containers in podman

this is the first pass at implementing init containers for podman pods.
init containersare made popular by k8s as a way to run setup for pods
before the pods standard containers run.

unlike k8s, we support two styles of init containers: always and
oneshot.  always means the container stays in the pod and starts
whenever a pod is started.  this does not apply to pods restarting.
oneshot means the container runs onetime when the pod starts and then is
removed.

Signed-off-by: Brent Baude <bbaude@redhat.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/libpod/define/container.go b/libpod/define/container.go
index f3125afa9..f0aca92aa 100644
--- a/libpod/define/container.go
+++ b/libpod/define/container.go
@@ -26,3 +26,13 @@ var RestartPolicyMap = map[string]string{
 	RestartPolicyOnFailure:     RestartPolicyOnFailure,
 	RestartPolicyUnlessStopped: RestartPolicyUnlessStopped,
 }
+
+// InitContainerTypes
+const (
+	// AlwaysInitContainer is an init container than runs on each
+	// pod start (including restart)
+	AlwaysInitContainer = "always"
+	// OneShotInitContainer is a container that only runs as init once
+	// and is then deleted.
+	OneShotInitContainer = "oneshot"
+)