Example /postinst script module for update_engine.

The "post-install" program (normally /system/postinst) is a program
stored in the new system but executed from the old system right before
finishing the update. This post-install step provides a way to perform
device-specific tasks needed for old devices to accept the new update
*before* attempting to boot it.

Currently, we don't require any particular task to be performed in this
step, so this is just an example post-install program with some
documentation. Nevertheless, update_engine payload major version 1
requires a /postinst script in the system partition. While we plan to
use payload major version 2 in Brillo, this patch allows to push images
to the pre-release version of update_engine.

Bug: 24194445
Test: `m` includes /postinst in a Brillo target.

Change-Id: I6397537119873c68e0a626a37137ececcf8f03d5

4 files changed, 256 insertions, 0 deletions

diff --git a/postinst/Android.mk b/postinst/Android.mk
new file mode 100644
index 00000000..b0dec050
--- /dev/null
+++ b/postinst/Android.mk
@@ -0,0 +1,30 @@
+#
+# Copyright (C) 2015 The Android Open Source Project
+#
+# 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.
+#
+
+LOCAL_PATH:= $(call my-dir)
+
+include $(CLEAR_VARS)
+LOCAL_MODULE:= postinst_example
+LOCAL_MODULE_TAGS := optional
+LOCAL_MODULE_CLASS := EXECUTABLES
+LOCAL_SRC_FILES := postinst.sh
+
+# Create a symlink from /postinst to our default post-install script in the
+# same filesystem as /postinst.
+# TODO(deymo): Remove this symlink and add the path to the product config.
+LOCAL_POST_INSTALL_CMD := \
+    $(hide) ln -sf bin/postinst_example $(TARGET_OUT)/postinst
+include $(BUILD_PREBUILT)
diff --git a/postinst/MODULE_LICENSE_APACHE2 b/postinst/MODULE_LICENSE_APACHE2
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/postinst/MODULE_LICENSE_APACHE2
diff --git a/postinst/NOTICE b/postinst/NOTICE
new file mode 100644
index 00000000..34bdaf1d
--- /dev/null
+++ b/postinst/NOTICE
@@ -0,0 +1,190 @@
+
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diff --git a/postinst/postinst.sh b/postinst/postinst.sh
new file mode 100644
index 00000000..eb98e79f
--- /dev/null
+++ b/postinst/postinst.sh
@@ -0,0 +1,36 @@
+#!/system/bin/sh
+
+#
+# Copyright (C) 2015 The Android Open Source Project
+#
+# 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.
+#
+
+# This is an example post-install script. This script will be executed by the
+# update_engine right after finishing writing all the partitions, but before
+# marking the new slot as active.
+#
+# This script receives no arguments. argv[0] will include the absolute path to
+# the script, including the temporary directory where the new partition was
+# mounted.
+#
+# This script will run in the context of the old kernel and old system. Note
+# that the absolute path used in first line of this script (/system/bin/sh) is
+# indeed the old system's sh binary. If you use a compiled program, you might
+# want to link it statically or use a wrapper script to use the new ldso to run
+# your program (see the --generate-wrappers option in lddtree.py for example).
+#
+# If the exit code of this program is an error code (different from 0), the
+# update will fail and the new slot will not be marked as active.
+
+exit 0