elements: Add new openssh-server element

Add new 'openssh-server' element to ensure that openssh server
is installed and enabled during boot. This is mostly useful for
*-minimal images which do not come with openssh installed and/or
enabled in order to keep a small dependency footprint.

Change-Id: Ide15ee04f5de123dbc8ce4bb56d638d8a167c341

elements/debian/element-deps

@@ -1 +1,2 @@
 debian-minimal
+openssh-server

elements/debian/package-installs.yaml

@@ -1,4 +1,3 @@
-openssh-server:
 file:
 less:
 kbd:

elements/dynamic-login/element-deps

@@ -1,3 +1,3 @@
 dib-init-system
 install-static
-package-installs
+openssh-server

elements/local-config/element-deps

@@ -1 +1 @@
-package-installs
+openssh-server

elements/local-config/package-installs.yaml

@@ -1 +0,0 @@
-openssh-server:

elements/openssh-server/README.rst

@@ -0,0 +1,14 @@
+==============
+openssh-server
+==============
+This element ensures that openssh server is installed and enabled during boot.
+
+
+Note
+----
+Most cloud images come with the openssh server service installed and enabled
+during boot. However, certain cloud images, especially those created by the
+\*-minimal elements may not have it installed or enabled. In these cases,
+using this element may be helpful to ensure your image will accessible via SSH.
+It's usually helpful to combine this element with others such as the
+`runtime-ssh-host-keys`.

elements/openssh-server/element-deps

@@ -0,0 +1,3 @@
+dib-init-system
+package-installs
+runtime-ssh-host-keys

elements/openssh-server/pkg-map

@@ -0,0 +1,10 @@
+{
+  "family": {
+    "suse": {
+      "openssh-server": "openssh"
+    },
+    "gentoo": {
+      "openssh-server": "openssh"
+    }
+  }
+}

elements/openssh-server/post-install.d/80-enable-sshd-service

@@ -0,0 +1,29 @@
+#!/bin/bash
+
+if [ "${DIB_DEBUG_TRACE:-0}" -gt 0 ]; then
+    set -x
+fi
+set -eu
+set -o pipefail
+
+case "$DIB_INIT_SYSTEM" in
+    upstart)
+        # nothing to do
+        exit 0
+        ;;
+    systemd)
+        if [[ $DISTRO_NAME = "ubuntu" || $DISTRO_NAME = "debian" ]]; then
+            systemctl enable ssh.service
+        else
+            systemctl enable sshd.service
+        fi
+        ;;
+    openrc)
+        # let dib-init-system's postinstall handle enabling init scripts
+        exit 0
+        ;;
+    *)
+        echo "Unsupported init system"
+        exit 1
+        ;;
+esac

releasenotes/notes/openssh-server-0f6d065748a2fc18.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - New openssh-server element to ensure that the openssh
+    server is installed and enabled during boot.