journal-to-console: element to send systemd journal to console

This element configures systemd to send its journal to the console,
which can then be retreived by server commands.  In the case of
nodepool, if the image failed to boot the console will be dumped into
the logs when nodepool decides the node is not responding.  Having
this can be very helpful diagnosing early boot errors.

Needed-By: https://review.opendev.org/#/c/669787/
Change-Id: I6b6df7023acb6b2f967b84840bc4b542ebc03727

diskimage_builder/elements/journal-to-console/README.rst

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+==================
+journal-to-console
+==================
+
+Configure systemd's journal to send all logs to console.  Useful for
+debugging issues before you can log into a host, such as network or
+authentication issues.
+
+The console can be retrieved from an OpenStack cloud with a command
+such as ``openstack console log show <server>``.

diskimage_builder/elements/journal-to-console/post-install.d/30-journal-to-console

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+#!/bin/bash
+#
+# Copyright 2019 Red Hat, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+if [ ${DIB_DEBUG_TRACE:-1} -gt 0 ]; then
+    set -x
+fi
+set -eu
+set -o pipefail
+
+mkdir -p /etc/systemd/journald.conf.d
+
+cat > /etc/systemd/journald.conf.d/log-to-console.conf << EOF
+[Journal]
+ForwardToConsole=true
+EOF

releasenotes/notes/journal-console-752b46542ec5595e.yaml

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+---
+features:
+  - |
+    The ``journal-to-console`` element is added to allow forwarding
+    systemd output to the host console.  This is useful for debugging
+    early boot issues.