containerfile: add support for Docker

In some build environments Docker is already installed - and adding
podman is not an option.  Add a new variable to toggle this, and
rename the now incorrectly titled DIB_CONTAINERFILE_PODMAN_ROOT to
just ...RUNTIME_ROOT to match.

Change-Id: I677e4f491b40360dceabdf4f2a9e64c7cb493dc7

diskimage_builder/elements/containerfile/README.rst

@@ -8,11 +8,14 @@ Dockerfiles).
 Usually this element will be called via a more specific distro element
 which provides an environment for building a full image.  This element
 will search active elements for a container file located in
-`containerfiles/${DIB_RELEASE}`.
+``containerfiles/${DIB_RELEASE}``.
 
 Alternatively, to use this element directly supply the path to a
 container file in the environment variable
-`DIB_CONTAINERFILE_DOCKERFILE`.
+``DIB_CONTAINERFILE_DOCKERFILE``.
 
-Set ``DIB_CONTAINERFILE_PODMAN_ROOT`` to ``1`` to run `podman` as
-`root`.
+Set ``DIB_CONTAINERFILE_RUNTIME`` to ``docker`` to use Docker for building
+images (default is ``podman``).
+
+Set ``DIB_CONTAINERFILE_RUNTIME_ROOT`` to ``1`` to run the runtime
+(Docker or ``podman``, per above) as ``root``.

diskimage_builder/elements/containerfile/root.d/08-containerfile

@@ -21,6 +21,13 @@ fi
 set -eu
 set -o pipefail
 
+: "${DIB_CONTAINERFILE_RUNTIME:=podman}"
+
+# Convert the old value which was podman specific
+if [[ "${DIB_CONTAINERFILE_PODMAN_ROOT:-0}" != '0' ]]; then
+    DIB_CONTAINERFILE_RUNTIME_ROOT=1
+fi
+
 if [ -f ${TARGET_ROOT}/.extra_settings ] ; then
     . ${TARGET_ROOT}/.extra_settings
 fi
@@ -52,7 +59,7 @@ DIB_CONTAINER_CONTEXT=${DIB_CONTAINER_CONTEXT:-${DIB_IMAGE_CACHE}/containerfile}
 
 mkdir -p $DIB_CONTAINER_CONTEXT
 
-if [[ ${DIB_CONTAINERFILE_PODMAN_ROOT:-0} -gt 0 ]]; then
+if [[ ${DIB_CONTAINERFILE_RUNTIME_ROOT:-0} -gt 0 ]]; then
     _sudo="sudo"
 else
     _sudo=""
@@ -63,17 +70,17 @@ _podman_export_container="dib-tmp-export-$RANDOM"
 
 function podman_cleanup() {
     echo "Cleaning up container ${_podman_export_container}"
-    ${_sudo} podman rm ${_podman_export_container} || true
+    ${_sudo} ${DIB_CONTAINERFILE_RUNTIME} rm ${_podman_export_container} || true
     echo "Cleaning up build image ${_podman_build_image}"
-    ${_sudo} podman rmi ${_podman_build_image} || true
+    ${_sudo} ${DIB_CONTAINERFILE_RUNTIME} rmi ${_podman_build_image} || true
 }
 
 trap "podman_cleanup" EXIT
 
-${_sudo} podman build -t ${_podman_build_image} -f $DIB_CONTAINERFILE_DOCKERFILE $DIB_CONTAINER_CONTEXT
-${_sudo} podman run --name ${_podman_export_container} -d ${_podman_build_image} /bin/sh
+${_sudo} ${DIB_CONTAINERFILE_RUNTIME} build -t ${_podman_build_image} -f $DIB_CONTAINERFILE_DOCKERFILE $DIB_CONTAINER_CONTEXT
+${_sudo} ${DIB_CONTAINERFILE_RUNTIME} run --name ${_podman_export_container} -d ${_podman_build_image} /bin/sh
 # NOTE(ianw) 2021-11-10 the tar must always be sudo to write out the chroot files
 # as other uids
-${_sudo} podman export ${_podman_export_container} | sudo tar -C $TARGET_ROOT --numeric-owner -xf -
+${_sudo} ${DIB_CONTAINERFILE_RUNTIME} export ${_podman_export_container} | sudo tar -C $TARGET_ROOT --numeric-owner -xf -
 
 sudo rm -f ${TARGET_ROOT}/.extra_settings

roles/dib-functests/tasks/main.yaml

@@ -66,4 +66,4 @@
     DIB_OS_CI_YUM_REPOS: "{{ dib_gate_mirror_repos|default(omit) }}"
     # NOTE(ianw) 2021-10-15 : this might be our bullseye images
     # having issues with non-root podman.  This works for now.
-    DIB_CONTAINERFILE_PODMAN_ROOT: 1
+    DIB_CONTAINERFILE_RUNTIME_ROOT: 1