auto updates

Add support to auto-update containers running in systemd units as
generated with `podman generate systemd --new`.

`podman auto-update` looks up containers with a specified
"io.containers.autoupdate" label (i.e., the auto-update policy).

If the label is present and set to "image", Podman reaches out to the
corresponding registry to check if the image has been updated.  We
consider an image to be updated if the digest in the local storage is
different than the one of the remote image.  If an image must be
updated, Podman pulls it down and restarts the container.  Note that the
restarting sequence relies on systemd.

At container-creation time, Podman looks up the "PODMAN_SYSTEMD_UNIT"
environment variables and stores it verbatim in the container's label.
This variable is now set by all systemd units generated by
`podman-generate-systemd` and is set to `%n` (i.e., the name of systemd
unit starting the container).  This data is then being used in the
auto-update sequence to instruct systemd (via DBUS) to restart the unit
and hence to restart the container.

Note that this implementation of auto-updates relies on systemd and
requires a fully-qualified image reference to be used to create the
container.  This enforcement is necessary to know which image to
actually check and pull.  If we used an image ID, we would not know
which image to check/pull anymore.

Fixes: #3575
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

2 files changed, 5 insertions, 1 deletions

diff --git a/pkg/specgen/create.go b/pkg/specgen/create.go
index 99a99083b..aefbe7405 100644
--- a/pkg/specgen/create.go
+++ b/pkg/specgen/create.go
@@ -36,7 +36,7 @@ func (s *SpecGenerator) MakeContainer(rt *libpod.Runtime) (*libpod.Container, er
 		return nil, err
 	}
 
-	options = append(options, libpod.WithRootFSFromImage(newImage.ID(), s.Image))
+	options = append(options, libpod.WithRootFSFromImage(newImage.ID(), s.Image, s.RawImageName))
 
 	runtimeSpec, err := s.toOCISpec(rt, newImage)
 	if err != nil {
diff --git a/pkg/specgen/specgen.go b/pkg/specgen/specgen.go
index e1dfe4dc5..7a430652a 100644
--- a/pkg/specgen/specgen.go
+++ b/pkg/specgen/specgen.go
@@ -143,6 +143,10 @@ type ContainerStorageConfig struct {
 	// Conflicts with Rootfs.
 	// At least one of Image or Rootfs must be specified.
 	Image string `json:"image"`
+	// RawImageName is the unprocessed and not-normalized user-specified image
+	// name.  One use case for having this data at hand are auto-updates where
+	// the _exact_ user input is needed in order to look-up the correct image.
+	RawImageName string `json:"raw_image_name,omitempty"`
 	// Rootfs is the path to a directory that will be used as the
 	// container's root filesystem. No modification will be made to the
 	// directory, it will be directly mounted into the container as root.