src/devices/tech/ota/tools.jd

page.title=OTA Package Tools
@jd:body

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<p>The <a href="https://android.googlesource.com/platform/build/+/master/tools/
releasetools/ota_from_target_files">ota_from_target_files</a> tool provided in
<code>build/tools/releasetools</code> can build two types of package: <i>full
</i> and <i>incremental</i>. The tool takes the <i>target-files</i> .zip file
produced by the Android build system as input.</p>

<h2 id="full-updates">Full updates</h2>
<p>A <i>full</i> update is one where the entire final state of the device
(system, boot, and recovery partitions) is contained in the package. As long
as the device is capable of receiving the package and booting the recovery
system, the package can install the desired build regardless of the current
state of the device.</p>
<p>Example: Using the release tools to build a full update for the
hypothetical <b>tardis</b> device:</p>

<pre>
# first, build the target-files .zip
% <b>. build/envsetup.sh &amp;&amp; lunch tardis-eng</b>
% <b>mkdir dist_output</b>
% <b>make dist DIST_DIR=dist_output</b>
  [...]
% <b>ls -l dist_output/*target_files*</b>
-rw-r----- 1 user eng  69965275 Sep 29 15:51 tardis-target_files.zip
</pre>

<p>The target-files .zip contains everything needed to construct OTA packages.
</p>

<pre>
% <b>./build/tools/releasetools/ota_from_target_files \
    dist_output/tardis-target_files.zip ota_update.zip</b>
unzipping target target-files...
done.
% <b>ls -l ota_update.zip</b>
-rw-r----- 1 user eng 62236561 Sep 29 15:58 ota_update.zip
</pre>

<p>The ota_update.zip is now ready to be sent to test devices (everything is
signed with the test key). For user devices, generate and use your own private
keys as detailed in <a href="{@docRoot}devices/tech/ota/sign_builds
.html">Signing builds for release</a>.

<h2 id="incremental-updates">Incremental updates</h2>
<p>An <i>incremental</i> update contains a set of binary patches to be applied
to the data already on the device. This can result in considerably smaller
update packages:</p>
<ul>
<li>Files that have not changed don't need to be included.</li>
<li>Files that have changed are often very similar to their previous versions,
so the package need only contain an encoding of the differences between the
two files.</li></ul>
<p>You can install the incremental update package only on a device that has
the old or source build used when constructing the package. To build an
incremental update, you need the target_files .zip from the previous build
(the one you want to update <i>from</i>) as well as the target_files .zip from
the new build.</p>

<pre>
% <b>./build/tools/releasetools/ota_from_target_files \
    -i PREVIOUS-tardis-target_files.zip \  </b># make incremental from this older version<b>
    dist_output/tardis-target_files.zip incremental_ota_update.zip</b>
unzipping target target-files...
unzipping source target-files...
   [...]
done.
% <b>ls -l incremental_ota_update.zip</b>
-rw-r----- 1 user eng 1175314 Sep 29 16:10 incremental_ota_update.zip
</pre>

<p>This build is very similar to the previous build, and the incremental
update package is much smaller than the corresponding full update (about 1 MB
instead of 60 MB).</p>
<p class="note"><strong>Note:</strong> To generate a
<a href="{@docRoot}devices/tech/ota/block.html">block-based OTA</a>
for subsequent updates, pass the <code>--block</code> option to
<code>ota_from_target_files</code>.</p>
<p>Distribute an incremental package only to devices running exactly the same
previous build used as the incremental package's starting point. Attempting to
install the incremental package on a device with some other build results in
the recovery error icon. Rebooting the device at this point returns the user
to the old system; the package verifies the previous state of all the files it
updates before touching them, so the device should not be left in a half
upgraded state if this occurs.</p>

<h2 id="update-packages">Update packages</h2>
<p>An update package (<code>ota_update.zip</code>,
<code>incremental_ota_update.zip</code>) is a .zip file that contains the
executable binary <code>META-INF/com/google/android/update-binary</code>. After
verifying the signature on the package, recovery extracts this binary to
<code>/tmp</code> and runs it, passing the following arguments:</p>
<ul>
<li><b>Update binary API version number</b>. If the arguments passed to the
update binary change, this number is incremented.</li>
<li><b>File descriptor of the <i>command pipe</i></b>. The update program can
use this pipe to send commands back to the recovery binary (mostly for UI
changes such as indicating progress to the user).</li>
<li><b>Filename of the update package .zip file</b>.</li>
</ul>
<p>A recovery package can use any statically-linked binary as the update
binary. The OTA package construction tools use the updater program (source in
<code>bootable/recovery/updater</code>), which provides a simple scripting
language that can do many installation tasks. You can substitute any other
binary running on the device.</p>
<p>For details on the updater binary, edify syntax, and builtin functions, see
<a href="{@docRoot}devices/tech/ota/inside_packages.html">Inside OTA Packages
</a>.