Introduce manual setting of DIB_INIT_SYSTEM

The current implementation evauates the dib-init-system
script too early.  Also it looks that there is no simple
way of getting the info about the init system automatically:
another element can install (later on) a different
init system.  Therefore the only reliable way of setting
this is manual.

Change-Id: I6e9ffa1bdb3154f488f4fd335b197699b86aacd4
Signed-off-by: Andreas Florath <andreas@florath.net>

diskimage_builder/elements/debian-minimal/environment.d/10-debian-minimal.bash

@@ -1,5 +1,6 @@
 export DISTRO_NAME=debian
 export DIB_RELEASE=${DIB_RELEASE:-stable}
+export DIB_INIT_SYSTEM=systemd
 
 if [ -n "${DIB_DEBIAN_DISTRIBUTION_MIRROR:-}" ]; then
     DIB_DISTRIBUTION_MIRROR=$DIB_DEBIAN_DISTRIBUTION_MIRROR

diskimage_builder/elements/dib-init-system/README.rst

@@ -2,9 +2,7 @@
 dib-init-system
 ===============
 
-Installs a script (dib-init-system) which outputs the type of init system in
-use on the target image. Also sets an environment variable ``DIB_INIT_SYSTEM``
-to this value.
+Element that handles aspects of the used target's init system.
 
 Any files placed in a ``init-scripts/INIT_SYSTEM`` directory inside the
 element will be copied into the appropriate directory if ``INIT_SYSTEM``
@@ -14,5 +12,6 @@ Environment Variables
 ---------------------
 
 DIB_INIT_SYSTEM
-  :Description: One of upstart, systemd, or sysv depending on the init system
-    in use for the target image.
+  :Description: One of ``upstart``, ``systemd``, ``openrc`` or
+    ``sysv`` depending on the init system in use for the target image.
+    This should be set automatically by your platform elements.

diskimage_builder/elements/dib-init-system/dib-init-system

@@ -1,33 +0,0 @@
-#!/bin/bash
-
-if [ ${DIB_DEBUG_TRACE:-0} -gt 0 ]; then
-    set -x
-fi
-set -eu
-set -o pipefail
-
-# Debian Jessie and Debian Stretch use /bin/systemctl.
-# (/sbin/init is only available if systemd-sysv is installed.)
-
-if [ -f /usr/bin/systemctl -o -f /bin/systemctl ]; then
-    echo "systemd"
-elif [[ -f /sbin/initctl ]]; then
-    echo "upstart"
-elif [[ -f /etc/gentoo-release ]]; then
-    if [[ -z GENTOO_PROFILE ]]; then
-        if [[ "${GENTOO_PROFILE}" =~ systemd ]]; then
-            echo "systemd"
-        fi
-    else
-        echo "openrc"
-    fi
-elif [[ -f /sbin/init ]]; then
-    if [[ -f /bin/systemd ]]; then
-        echo "systemd"
-    else
-        echo "sysv"
-    fi
-else
-    echo "Unknown init system"
-    exit 1
-fi

diskimage_builder/elements/dib-init-system/environment.d/10-dib-init-system.bash

@@ -1,2 +0,0 @@
-DIB_INIT_SYSTEM=$(PATH="$PATH:$(dirname $BASH_SOURCE)/.." dib-init-system)
-export DIB_INIT_SYSTEM

diskimage_builder/elements/dib-init-system/environment.d/99-dib-init-system

@@ -0,0 +1,30 @@
+#
+# This runs last in the environment to ensure DIB_INIT_SYSTEM is set.
+# We expect the base environments to set this variable particular to
+# their platform.  Note we used to try and guess this automatically
+# inside the chroot, but there's a chicken-and-egg issue when you're
+# building from scratch and you're guessing before you've even
+# installed the init system.
+#
+
+if [ -z "${DIB_INIT_SYSTEM:-}" ]; then
+    echo "DIB_INIT_SYSTEM is not set! Can not continue"
+    exit 1
+fi
+
+# whitelist known systems
+case $DIB_INIT_SYSTEM in
+    upstart)  ;;
+    openrc)   ;;
+    systemd)  ;;
+    sysv)     ;;
+    *)
+        echo "Unrecognised init system: ${DIB_INIT_SYSTEM}!"
+        echo "Can not continue"
+        exit 1
+esac
+
+# Tell emacs to use shell-mode
+# Local variables:
+# mode: sh
+# End:

diskimage_builder/elements/dib-init-system/pre-install.d/04-dib-init-system

@@ -6,4 +6,16 @@ fi
 set -eu
 set -o pipefail
 
-install -m 0755 -o root -g root $(dirname $0)/../dib-init-system /usr/bin/
+FILE=/usr/local/bin/dib-init-system
+
+# This is a dummy script that simply echos the output of
+# ${DIB_INIT_SYSTEM}.  This script used to try and guess the init
+# system, but that doesn't work.  This script is deprecated.
+
+cat > ${FILE} <<EOF
+#!/bin/bash
+echo ${DIB_INIT_SYSTEM}
+EOF
+
+chown root:root ${FILE}
+chmod 775 ${FILE}

diskimage_builder/elements/gentoo/environment.d/00-gentoo-envars.bash

@@ -21,3 +21,5 @@ fi
 for (( i=0; i<${#GENTOO_EMERGE_ENV[@]}; i++ )); do
     eval export "${GENTOO_EMERGE_ENV[i]}"
 done
+
+export DIB_INIT_SYSTEM=systemd

diskimage_builder/elements/opensuse-minimal/environment.d/10-opensuse-distro-name.bash

@@ -2,3 +2,4 @@ export DISTRO_NAME=opensuse
 DIB_RELEASE=${DIB_RELEASE:-15.1}
 export DIB_RELEASE=${DIB_RELEASE,,}
 export DIB_OPENSUSE_PATTERNS=patterns-openSUSE-base
+export DIB_INIT_SYSTEM=systemd

diskimage_builder/elements/opensuse/environment.d/10-opensuse-distro-name.bash

@@ -1,6 +1,7 @@
 export DISTRO_NAME=opensuse
 export DIB_RELEASE=${DIB_RELEASE:-15.1}
 export DIB_OPENSUSE_PATTERNS=patterns-openSUSE-base
+export DIB_INIT_SYSTEM=systemd
 case ${DIB_RELEASE} in
     # Old Leap releases
     42*) export OPENSUSE_REPO_DIR=openSUSE_Leap_${DIB_RELEASE} ;;

diskimage_builder/elements/redhat-common/environment.d/50-redhat-common

@@ -1 +1,2 @@
 export DIB_DISABLE_KERNEL_CLEANUP=${DIB_DISABLE_KERNEL_CLEANUP:-0}
+export DIB_INIT_SYSTEM=systemd

diskimage_builder/elements/ubuntu-common/environment.d/11-ubuntu-init-system.bash

@@ -0,0 +1,5 @@
+if [[ ${DIB_RELEASE} == "trusty" ]]; then
+    export DIB_INIT_SYSTEM=upstart
+else
+    export DIB_INIT_SYSTEM=systemd
+fi

releasenotes/notes/dib-init-system-5647bad17a01c602.yaml

@@ -0,0 +1,14 @@
+---
+deprecations:
+  - |
+    The ``dib-init-system`` element installs a utility
+    ``/usr/local/bin/dib-init-system`` which would try to guess the
+    init system (systemd, etc.).  This was called from
+    ``environment.d`` files, which means that in phases outside the
+    chroot it was attempting to query the init system of the build
+    host.  This completely fails in a situation such as running inside
+    a container without a full init system.  To avoid this issue, each
+    OS element will set DIB_INIT_SYSTEM directly.  The
+    ``dib-init-system`` script was not really intended to be called
+    directly, but will now just report the value of
+    ``DIB_INIT_SYSTEM``.