Merge "docs: editorial revisions to the bmgr tool doc" into froyo

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  <h2>bmgr quickview</h2>

<p><code>bmgr</code> lets you inspect and control the backup/restore system on an Android device.

<p><code>bmgr</code> lets you control the backup/restore system on an Android device.

  <h2>In this document</h2>

  <ol>

<li><a href="#transports">About backup transports</a></li>

<li><a href="#restoresets">About restore sets</a></li>

<li><a href="#backup">Forcing a backup operation</a></li>

<li><a href="#restore">Forcing a restore operation</a></li>

<li><a href="#other">Other commands</a></li>

<li><a href="#backup">Forcing a Backup Operation</a></li>

<li><a href="#restore">Forcing a Restore Operation</a></li>

<li><a href="#other">Other Commands</a></li>

  </ol>

</div>

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<p><code>bmgr</code> is a shell tool that developers can use to interact with the Backup Manager

on Android devices supporting API version 8 or later.  It provides commands for inducing backup

and restore operations on demand so that you do not need to repeatedly wipe data or take similar

intrusive steps to test the operation of an application's backup agent.  These commands are

<p><code>bmgr</code> is a shell tool you can use to interact with the Backup Manager

on Android devices supporting API Level 8 or greater.  It provides commands to induce backup

and restore operations so that you don't need to repeatedly wipe data or take similar

intrusive steps in order to test your application's backup agent.  These commands are

accessed via the <a href="{@docRoot}guide/developing/tools/adb.html">adb</a> shell.

<p>There are a couple of basic concepts used by the Backup Manager that are built into the way

that <code>bmgr</code> operates.  These are <a href="#transports">backup transports</a> and

<a href="#restoresets">restore sets</a>.

<a name="transports"></a>

<h2>About backup transports</h2>

<h2 id="backup">Forcing a Backup Operation</h2>

<p>A <em>backup transport</em> is the code module responsible for moving backup and restore data

to and from some storage location.  A device can have multipe transports installed, though only

one is active at any given time.  Transports are identified by name.  You can see what

transports are available on your device or emulator by running the

<code>bmgr list transports</code> command:

<p>Normally, your application must notify the Backup Manager when its data has changed, via {@link

android.app.backup.BackupManager#dataChanged()}. The Backup Manager will then invoke your

backup agent's {@link

android.app.backup.BackupAgent#onBackup(ParcelFileDescriptor,BackupDataOutput,ParcelFileDescriptor)

onBackup()} implementation at some time in the future. However, instead of calling {@link

android.app.backup.BackupManager#dataChanged()}, you can invoke a backup request from the command

line by running the <code>bmgr backup</code> command:

    <pre>adb shell bmgr list transports</pre>

    <pre class="no-pretty-print">adb shell bmgr backup <em>&lt;package&gt;</em></pre>

<p>The output of this command is a list of the transports available on the device.  The currently

active transport is flagged with a <code>*</code> character.  Transport names may look like

component names -- for example, <code>android/com.android.internal.backup.LocalTransport</code> --

but they need not be, and the strings are never used as direct class references.  The use of

a component-like naming scheme is simply for purposes of preventing name collisions.

<p><code><em>&lt;package&gt;</em></code> is the formal package name of the application you wish to

schedule for

backup. When you execute this backup command, your application's backup agent will be invoked to

perform a backup operation at some time in the future (via your {@link

android.app.backup.BackupAgent#onBackup(ParcelFileDescriptor,BackupDataOutput,ParcelFileDescriptor)

onBackup()} method), though there is no guarantee when it will occur. However, you can force all

pending backup operations to run immediately by using the <code>bmgr run</code> command:

<p>You can change which transport is currently active from the command line as well:

    <pre class="no-pretty-print">adb shell bmgr run</pre>

    <pre>adb shell bmgr transport NAME</pre>

<p>This causes a backup pass to execute immediately, invoking the backup agents of all applications

that had previously called {@link android.app.backup.BackupManager#dataChanged()} since the

last backup operation, plus any applications which had been manually scheduled for

backup via <code>bmgr backup</code>.

<p>where <code>NAME</code> is one of the names as printed by the <code>bmgr list transports</code>

command.  From this point forward, backup and restore operations will be directed through the

newly-selected transport.  Backup state tracking is managed separately for each transport, so

switching back and forth between them will not corrupt the saved state.

<a name="restoresets"></a>

<h2>About restore sets</h2>

<h2 id="restore">Forcing a Restore Operation</h2>

<p>All of the application data that a device has written to a given backup transport is tracked

together, and is collectively sometimes called a <em>restore set,</em> because the typical use

of the data set is during restore operations.  Each time a device is initially provisioned, a

new data set is established.  The user can get a listing of all the data sets that can be

restored through the current transport by running this shell command:

<p>Unlike backup operations, which are batched together and run on an occasional basis, restore

operations execute immediately.  The Backup Manager currently provides two kinds of restore

operations.  The first kind restores an entire device with the data that has been backed up.  This

is typically performed only when a device is first provisioned (to replicate settings and other

saved state from the user's previous device) and is an operation that only the system can

perform. The second kind of restore operation restores

a single application to its "active" data set; that is, the application will abandon its current

data and revert to the last-known-good data that is held in the current backup image. You can

invoke this second restore operation with the {@link

android.app.backup.BackupManager#requestRestore(RestoreObserver) requestRestore()} method. The

Backup Manager will then invoke your backup agent's {@link

android.app.backup.BackupAgent#onRestore(BackupDataInput,int,ParcelFileDescriptor)

onRestore()} implementation.

    <pre>adb shell bmgr list sets</pre>

<p>While testing your application, you can immediately invoke the restore operation (bypassing the

{@link android.app.backup.BackupManager#requestRestore(RestoreObserver) requestRestore()} method)

for your application by using the <code>bmgr restore</code> command:

<p>The output is listing of available restore sets, one per line.  The first item on each line is

a <em>token,</em> a number in hexadecimal that identifies the restore set to the transport.  After

that is a string that may provide some brief identifying information about the restore set.  Only

the token is actually used within the backup and restore mechanism.

    <pre class="no-pretty-print">adb shell bmgr restore <em>&lt;package&gt;</em></pre>

<p><code><em>&lt;package&gt;</em></code> is the formal Java-style package name of the application

participating in the backup/restore mechanism, which you would like to restore. The Backup

Manager will immediately instantiate the application's backup agent and invoke it for restore. This

will happen even if your application is not currently running.

<a name="backup"></a>

<h2>Forcing a backup operation</h2>

<p>Normally, applications notify the backup manager directly that their data has changed, in

response to which the backup manager will make sure to invoke that application's agent when the

next backup operation is run.  You can simulate this manually from the command line if you wish,

by running this shell command:

    <pre>adb shell bmgr backup PACKAGE</pre>

<p><code>PACKAGE</code> is the formal package name of the application you wish to schedule for

backup.  At this point you know that the application's agent will be invoked for backup at some

point in the future, though there is no hard guarantee of when that will occur.  You can force

all pending backup operations to run immediately by using the following command:

    <pre>adb shell bmgr run</pre>

<h2 id="other">Other Commands</h2>

<p>This causes a backup pass to execute immediately, invoking the agents of all applications that

had called <code>BackupManager.dataChanged()</code> since the time of the last backup operation,

plus any applications which had been manually scheduled for backup via

<code>bmgr backup PACKAGE</code>.

<p>The data for a single application can be erased from the active data set on demand.  This is

very useful while you're developing a backup agent, in case bugs lead you to write corrupt data

or saved state information. You can wipe an application's data with the <code>bmgr wipe</code>

command:

    <pre class="no-pretty-print">adb shell bmgr wipe <em>&lt;package&gt;</em></pre>

<a name="restore"></a>

<h2>Forcing a restore operation</h2>

<p><code><em>&lt;package&gt;</em></code> is the formal package name of the application whose data

you wish to

erase.  The next backup operation that the application's agent processes will look as

though the application had never backed anything up before.

<p>Unlike backup operations, which are batched together and run on an occasional basis, restore

operations execute immediately.  The backup manager currently provides two kinds of restore

operations.  The first restores an entire device with the data from a given restore set.  This

is typically only performed when a device is first provisioned, to replicate settings and other

such saved state from the user's previous device.  The second kind of restore operation restores

a single application from the <em>active</em> data set; that is, from the data set currently

being written to by backup operations.  This second form is available as part of the public API.

It allows applications to abandon their current data and revert to the last-known-good data as

represented in their current backup image.

<p>You can see whether the Backup Manager is operational at all with the <code>bmgr

enabled</code> command:

<p>A full-system restore operation can be initiated with this shell command:

    <pre class="no-pretty-print">adb shell bmgr enabled</pre>

    <pre>adb shell bmgr restore TOKEN</pre>

<p>This might be useful if your application's backup agent is never being invoked for backup, to

verify whether the operating system thinks it should be performing such operations at all.</p>

<p>where <code>TOKEN</code> is the desired restore set's token as printed out by the <code>bmgr

list sets</code> command.  <strong>Warning!</strong>  This operation will <em>replace</em> the

data of all backup-enabled applications with the contents of the given restore set.  Be careful,

and be aware of the potential consequences.

<p>You can also directly disable or enable the Backup Manager with this command:

<p>A single-application restore operation does not reference a restore set token; it always uses

the data from the currently active data set.  You can induce such an operation from the command

line like this:

    <pre class="no-pretty-print">adb shell bmgr enable <em>&lt;boolean&gt;</em></pre>

    <pre>adb shell bmgr restore PACKAGE</pre>

<p><code><em>&lt;boolean&gt;</em></code> is either <code>true</code> or <code>false</code>.

This is equivalent to disabling or enabling backup in the device's main Settings UI.</p>

<p><code>PACKAGE</code> is the formal package name of an application that is participating in the

backup/restore mechanism.  The backup manager will immediately instantiate the application's

agent and invoke it for restore.

<p class="warning"><strong>Warning!</strong>  When backup is disabled, the current backup transport

will explicitly wipe

the entire active data set from its backend storage.  This is so that when a user says

they do <em>not</em> want their data backed up, the Backup Manager respects that wish.  No further

data will be saved from the device, and no restore operations will be possible, unless the Backup

Manager is re-enabled (either through Settings or through the above <code>bmgr</code> command).

<a name="other"></a>

<h2>Other commands</h2>

<p>The data for a single application can be erased from the active data set on demand.  This is

very useful during development of backup agents, in case bugs lead you to write corrupt data

or saved state information.  The shell command for wiping an application's data is this:

    <pre>adb shell bmgr wipe PACKAGE</pre>

<p><code>PACKAGE</code> is the formal package name of the application whose data you wish to

erase.  The next backup operation that the application's agent processes will look as

though the application had never backed anything up before.

<!-- The following is not useful to applications, but may be some useful information some day...

<h2 id="transports">Applying a Backup Transport</h2>

<p>A "backup transport" is the code module responsible for moving backup and restore data

to and from some storage location.  A device can have multipe transports installed, though only

one is active at any given time.  Transports are identified by name.  You can see what

transports are available on your device or emulator by running the

<code>bmgr list transports</code> command:

    <pre class="no-pretty-print">adb shell bmgr list transports</pre>

<p>The output of this command is a list of the transports available on the device.  The currently

active transport is flagged with a <code>*</code> character.  Transport names may look like

component names (for example, <code>android/com.android.internal.backup.LocalTransport</code>),

but they need not be, and the strings are never used as direct class references.  The use of

a component-like naming scheme is simply for purposes of preventing name collisions.

<p>You can change which transport is currently active from the command line as well:

    <pre class="no-pretty-print">adb shell bmgr transport <em>&lt;name&gt;</em></pre>

<p><code><em>&lt;name&gt;</em></code> is one of the names as printed by the <code>bmgr list

transports</code>

command.  From this point forward, backup and restore operations will be directed through the

newly-selected transport.  Backup state tracking is managed separately for each transport, so

switching back and forth between them will not corrupt the saved state.

<p>You can see whether the backup manager is operational at all by running this command:

<h2 id="restoresets">Viewing Restore Sets</h2>

    <pre>adb shell bmgr enabled</pre>

<p>All of the application data that a device has written to its backup transport is tracked

as a group that is collectively called a "restore set," because each data set is

most often manipulated during a restore operation. When a device is provisioned for the first

time, a new restore set is established.  You can get a listing of all the restore sets available to

the current transport by running the <code>bmgr list sets</code> command:

<p>This might be useful if your application's agent is never being invoked for backup, to verify

whether the operating system thinks it should be performing such operations at all.  You can also

directly disable or enable the backup manager with this command:

    <pre class="no-pretty-print">adb shell bmgr list sets</pre>

    <pre>adb shell bmgr enable BOOLEAN</pre>

<p>The output is a listing of available restore sets, one per line.  The first item on each line is

a token (a hexadecimal value that identifies the restore set to the transport).  Following

the token is a string that briefly identifies the restore set.

Only the token is used within the backup and restore mechanism.

<p>where <code>BOOLEAN</code> is either <code>true</code> or <code>false</code>.  This is

equivalent to disabling or enabling backup in the device's main Settings UI.

<strong>Warning!</strong>  When backup is disabled, the current transport will explicitly wipe

the entire active data set from its backend storage.  This is so that when a user says that no,

they do not want their data backed up, the backup manager respects that wish.  No further data

will be saved from the device, and no restore operations will be possible, unless the backup

manager is re-enabled (either through Settings or through the above <code>bmgr</code> command).

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