docs/android_emulator.md - chromium/src - Git at Google

 # Using an Android Emulator
 Always use x86 emulators (or x86\_64 for testing 64-bit APKs). Although arm
 emulators exist, they are so slow that they are not worth your time.

 [TOC]

 ## Building for Emulation
 You need to target the correct architecture via GN args:
 ```gn
 target_cpu = "x86"  # or "x64" if you have an x86_64 emulator
 ```

 ## Running an Emulator

 ### Googler-only Emulator Instructions

 See http://go/clank-emulator/

 ### Using Prebuilt AVD configurations.

 Chromium has a set of prebuilt AVD configurations stored as CIPD packages.
 These are used by various builders to run tests on the emulator. Their
 configurations are currently stored in [`//tools/android/avd/proto`](../tools/android/avd/proto/).
 You can run this command to list them:
 ```sh
 tools/android/avd/avd.py list
 ```

 | Configurations | Android Version | Form Factor | Builder |
 |:-------------- |:--------------- |:------- |:---------- |:------- |
 | `generic_android26.textpb` | 8.0 (O) | Phone | [android-oreo-x86-rel][android-oreo-x86-rel] |
 | `generic_android27.textpb` | 8.1 (O_MR1) | Phone | N/A |
 | `android_28_google_apis_x86.textpb` | 9 (P) | Phone | [android-pie-x86-rel][android-pie-x86-rel] |
 | `android_29_google_apis_x86.textpb` | 10 (Q) | Phone | N/A |
 | `android_30_google_apis_x86.textpb` | 11 (R) | Phone | [android-11-x86-rel][android-11-x86-rel] |
 | `android_31_google_apis_x64.textpb` | 12 (S) | Phone | [android-12-x64-rel][android-12-x64-rel] |
 | `android_32_google_apis_x64_foldable.textpb` | 12L (S_V2) | Foldable Phone | [android-12l-x64-dbg-tests][android-12l-x64-dbg-tests] |
 | `android_32_google_apis_x64_foldable_landscape.textpb` | 12L (S_V2) | Foldable Phone (Landscape) | [android-12l-landscape-x64-dbg-tests][android-12l-landscape-x64-dbg-tests] |
 | `android_33_google_apis_x64.textpb` | 13 (T) | Phone | [android-13-x64-rel][android-13-x64-rel] |
 | `android_34_google_apis_x64.textpb` | 14 (U) | Phone | [android-14-x64-rel][android-14-x64-rel] |
 | `android_35_google_apis_x64.textpb` | 15 (V) | Phone | [android-15-x64-rel][android-15-x64-rel] |
 | `android_35_google_apis_x64_tablet.textpb` | 15 (V) | Tablet | [android-15-tablet-x64-dbg-tests][android-15-tablet-x64-dbg-tests] |
 | `android_35_google_apis_x64_tablet_landscape.textpb` | 15 (V) | Tablet (Landscape) | [android-15-tablet-landscape-x64-dbg-tests][android-15-tablet-landscape-x64-dbg-tests] |

 You can use these configuration files to run the same emulator images locally.

 [android-oreo-x86-rel]: https://ci.chromium.org/p/chromium/builders/ci/android-oreo-x86-rel
 [android-pie-x86-rel]: https://ci.chromium.org/p/chromium/builders/ci/android-pie-x86-rel
 [android-11-x86-rel]: https://ci.chromium.org/p/chromium/builders/ci/android-11-x86-rel
 [android-12-x64-rel]: https://ci.chromium.org/p/chromium/builders/ci/android-12-x64-rel
 [android-12l-x64-dbg-tests]: https://ci.chromium.org/p/chromium/builders/ci/android-12l-x64-dbg-tests
 [android-12l-landscape-x64-dbg-tests]: https://ci.chromium.org/p/chromium/builders/ci/android-12l-landscape-x64-dbg-tests
 [android-13-x64-rel]: https://ci.chromium.org/p/chromium/builders/ci/android-13-x64-rel
 [android-14-x64-rel]: https://ci.chromium.org/p/chromium/builders/ci/android-14-x64-rel
 [android-15-x64-rel]: https://ci.chromium.org/p/chromium/builders/ci/android-15-x64-rel
 [android-15-tablet-x64-dbg-tests]: https://ci.chromium.org/ui/p/chromium/builders/ci/android-15-tablet-x64-dbg-tests
 [android-15-tablet-landscape-x64-dbg-tests]: https://ci.chromium.org/ui/p/chromium/builders/ci/android-15-tablet-landscape-x64-dbg-tests

 > Note: New AVD configurations for LOCAL development are also available now,
 > whose file names end with `_local`, i.e. `*_local.textpb`.
 >
 > The only difference is that these configs has 12GB storage space instead of
 > 4GB on the non-local ones. Larger storage space makes it easier for developers
 > to install large APKs without hitting the space issue.

 #### Prerequisite

  * Make sure KVM (Kernel-based Virtual Machine) is enabled.
    See this
    [link](https://developer.android.com/studio/run/emulator-acceleration#vm-linux)
    from android studio for more details and instructions.

  * You need to have the permissions to use KVM.
    Use the following command to see if you are in group `kvm`:

    ```
      $ grep kvm /etc/group
    ```

    If your username is not shown in the group, add yourself to the group:

    ```
      $ sudo adduser $USER kvm
      $ newgrp kvm
    ```

    You need to log out and log back in so the new groups take effect.

 #### Running via the test runner

 The android test runner can run emulator instances on its own. In doing so, it
 starts the emulator instances, runs tests against them, and then shuts them
 down. This is how builders run the emulator.

 ##### Options

  * `--avd-config`

     To have the test runner run an emulator instance, use `--avd-config`:

     ```
       $ out/Debug/bin/run_base_unittests \
           --avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb
     ```

  * `--emulator-count`

     The test runner will launch one instance by default. To have it run multiple
     instances, use `--emulator-count`:

     ```
       $ out/Debug/bin/run_base_unittests \
           --avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
           --emulator-count 4
     ```

  * `--emulator-enable-network`

     The test runner runs the emulator without network access by default. To have
     it run with network access, use `--emulator-enable-network`:

     ```
     $ out/Debug/bin/run_base_unittests \
           --avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
           --emulator-enable-network
     ```

  * `--emulator-window`

     The test runner runs the emulator in headless mode by default. To have it run
     with a window, use `--emulator-window`:

     ```
       $ out/Debug/bin/run_base_unittests \
           --avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
           --emulator-window
     ```

 #### Running standalone

 The test runner will set up and tear down the emulator on each invocation.
 To manage emulator lifetime independently, use `tools/android/avd/avd.py`.

 ##### Options

  * `--avd-config`

     This behaves the same as it does for the test runner.

     ```
       $ tools/android/avd/avd.py start \
           --avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb
     ```

     > Note: `avd.py start` will start an emulator instance and then terminate.
     > To shut down the emulator, use `adb emu kill`.

  * `--enable-network`

     Like the test runner, `avd.py` runs the emulator without network access by
     default. To enable network access, use `--enable-network`:

     ```
       $ tools/android/avd/avd.py start \
           --avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
           --enable-network
     ```

  * `--emulator-window`

     Like the test runner, `avd.py` runs the emulator in headless mode by default.
     To have it run with a window, use `--emulator-window`:

     ```
       $ tools/android/avd/avd.py start \
           --avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
           --emulator-window
     ```

  * `--gpu-mode GPU_MODE`

     Override the mode of hardware OpenGL ES emulation indicated by the AVD.
     See "emulator -help-gpu" for a full list of modes.

  * `--no-read-only`

     `avd.py` runs the emulator in read-only mode by default. To run a modifiable
     emulator, use `--no-read-only`:

     ```
       $ tools/android/avd/avd.py start \
           --avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
           --no-read-only
     ```

  * `--wipe-data`

     Reset the /data partition to the factory defaults. This removes all user
     settings from the AVD.

     ```
       $ tools/android/avd/avd.py start \
           --avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
           --wipe-data
     ```

  * `--writable-system`

     Makes system & vendor image writable. It's necessary to run
     ```
     adb root
     adb remount
     ```
     after the emulator starts.

  * `--debug-tags`

     `avd.py` disables the emulator log by default. When this option is used,
     emulator log will be enabled. It is useful when the emulator cannot be
     launched correctly. See `emulator -help-debug-tags` for a full list of tags.
     Use `--debug-tags=all` if you want to output all logs (warning: it is quite
     verbose).

     ```
       $ tools/android/avd/avd.py start \
           --avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
           --debug-tags init,snapshot
     ```

 ### Using Your Own Emulator Image

 By far the easiest way to set up emulator images is to use Android Studio.
 If you don't have an [Android Studio project](android_studio.md) already, you
 can create a blank one to be able to reach the Virtual Device Manager screen.

 Refer to: https://developer.android.com/studio/run/managing-avds.html

 Where files live:
  * System partition images are stored within the sdk directory.
  * Emulator configs and data partition images are stored within
    `~/.android/avd/`.

 #### Creating an Image

 ##### Choosing a Skin

 Choose a skin with a small screen for better performance (unless you care about
 testing large screens).

 ##### Choosing an Image

 Android Studio's image labels roughly translate to the following:

 | AVD "Target" | Virtual Device Configuration tab | GMS? | Build Properties |
 | --- | --- | --- | --- |
 | Google Play | "Recommended" (the default tab) | This has GMS | `user`/`release-keys` |
 | Google APIs | "x86 Images" | This has GMS | `userdebug`/`dev-keys` |
 | No label | "x86 Images" | AOSP image, does not have GMS | `eng`/`test-keys` |

 *** promo
 **Tip:** if you're not sure which to use, choose **Google APIs** under the **x86
 Images** tab in the Virtual Device Configuration wizard.
 ***

 ##### Configuration

 "Show Advanced Settings" > scroll down:
 * Set internal storage to 4000MB (component builds are really big).
 * Set SD card to 1000MB (our tests push a lot of files to /sdcard).

 ##### Known Issues

  * Our test & installer scripts do not work with pre-MR1 Jelly Bean.
  * Component builds do not work on pre-KitKat (due to the OS having a max
    number of shared libraries).
  * Jelly Bean and KitKat images sometimes forget to mount /sdcard :(.
    * This causes tests to fail.
    * To ensure it's there: `adb -s emulator-5554 shell mount` (look for /sdcard)
    * Can often be fixed by editing `~/.android/avd/YOUR_DEVICE/config.ini`.
      * Look for `hw.sdCard=no` and set it to `yes`
  * The "Google APIs" Android L and M emulator images are configured to expect
    the "AOSP" WebView package (`com.android.webview`). This does not resemble
    production devices with GMS, which expect the ["Google WebView"
    configuration](/android_webview/docs/webview-providers.md#webview-provider-options)
    (`com.google.android.webview` on L and M). See [Removing preinstalled
    WebView](/android_webview/docs/build-instructions.md#Removing-preinstalled-WebView)
    if you need to install a local build or official build.


 #### Starting an Emulator from the Command Line

 Refer to: https://developer.android.com/studio/run/emulator-commandline.html.

 *** promo
 Ctrl-C will gracefully close an emulator.
 ***

 *** promo
 **Tip:** zsh users can add https://github.com/zsh-users/zsh-completions to
 provide tab completion for the `emulator` command line tool.
 ***

 #### Basic Command Line Use

 ```shell
 $ # List virtual devices that you've created:
 $ ~/Android/Sdk/emulator/emulator -list-avds
 $ # Start a named device:
 $ ~/Android/Sdk/emulator/emulator @EMULATOR_ID
 ```

 #### Running a Headless Emulator

 You can run an emulator without creating a window on your desktop (useful for
 `ssh`):
 ```shell
 $ ~/Android/Sdk/emulator/emulator -no-window @EMULATOR_ID
 $ # This also works for new enough emulator builds:
 $ ~/Android/Sdk/emulator/emulator-headless @EMULATOR_ID
 ```

 #### Running Multiple Emulators

 Tests are automatically sharded amongst available devices. If you run multiple
 emulators, then running test suites becomes much faster. Refer to the
 "Multiple AVD instances" section of these [emulator release notes](
 https://androidstudio.googleblog.com/2018/11/emulator-28016-stable.html)
 for more about how this works.
 ```shell
 $ # Start 8 emulators. Press Ctrl-C to stop them all.
 $ ( for i in $(seq 8); do ~/Android/Sdk/emulator/emulator @EMULATOR_ID -read-only & done; wait )
 $ # Start 12 emulators. More than 10 requires disabling audio on some OS's. Reducing cores increases parallelism.
 $ ( for i in $(seq 12); do ~/Android/Sdk/emulator/emulator @EMULATOR_ID -read-only -no-audio -cores 2 & done; wait )
 ```

 #### Writable system partition

 Unlike physical devices, an emulator's `/system` partition cannot be modified by
 default (even on rooted devices). If you need to do so (such as to remove a
 system app), you can start your emulator like so:
 ```shell
 $ ~/Android/Sdk/emulator/emulator -writable-system @EMULATOR_ID
 ```

 ## Using an Emulator
  * Emulators show up just like devices via `adb devices`
    * Device serials will look like "emulator-5554", "emulator-5556", etc.

 ## Emulator pros and cons

 ### Pros
  * **Compiles are faster.** Many physical devices are arm64, whereas emulators
    are typically x86 (32-bit). 64-bit builds may require 2 copies of the native
    library (32-bit and 64-bit), so compiling for an arm64 phone is ~twice as
    much work as for an emulator (for targets which support WebView).
  * **APKs install faster.** Since emulators run on your workstation, adb can
    push the APK onto the emulator without being [bandwidth-constrained by
    USB](https://youtu.be/Mzop8bXZI3E).
  * Emulators can be nice for working remotely. Physical devices usually require
    `scp` or ssh port forwarding to copy the APK from your workstation and
    install on a local device. Emulators run on your workstation, so there's **no
    ssh slow-down**.

 ### Cons
  * If you're investigating a hardware-specific bug report, you'll need a
    physical device with the actual hardware to repro that issue.
  * x86 emulators need a separate out directory, so building for both physical
    devices and emulators takes up more disk space (not a problem if you build
    exclusively for the emulator).
  * `userdebug`/`eng` emulators don't come with the Play Store installed, so you
    can't install third party applications. Sideloading is tricky, as not all
    third-party apps support x86.
	# Using an Android Emulator
	Always use x86 emulators (or x86\_64 for testing 64-bit APKs). Although arm
	emulators exist, they are so slow that they are not worth your time.

	[TOC]

	## Building for Emulation
	You need to target the correct architecture via GN args:
	```gn
	target_cpu = "x86" # or "x64" if you have an x86_64 emulator
	```

	## Running an Emulator

	### Googler-only Emulator Instructions

	See http://go/clank-emulator/

	### Using Prebuilt AVD configurations.

	Chromium has a set of prebuilt AVD configurations stored as CIPD packages.
	These are used by various builders to run tests on the emulator. Their
	configurations are currently stored in [`//tools/android/avd/proto`](../tools/android/avd/proto/).
	You can run this command to list them:
	```sh
	tools/android/avd/avd.py list
	```

	\| Configurations \| Android Version \| Form Factor \| Builder \|
	\|:-------------- \|:--------------- \|:------- \|:---------- \|:------- \|
	\| `generic_android26.textpb` \| 8.0 (O) \| Phone \| [android-oreo-x86-rel][android-oreo-x86-rel] \|
	\| `generic_android27.textpb` \| 8.1 (O_MR1) \| Phone \| N/A \|
	\| `android_28_google_apis_x86.textpb` \| 9 (P) \| Phone \| [android-pie-x86-rel][android-pie-x86-rel] \|
	\| `android_29_google_apis_x86.textpb` \| 10 (Q) \| Phone \| N/A \|
	\| `android_30_google_apis_x86.textpb` \| 11 (R) \| Phone \| [android-11-x86-rel][android-11-x86-rel] \|
	\| `android_31_google_apis_x64.textpb` \| 12 (S) \| Phone \| [android-12-x64-rel][android-12-x64-rel] \|
	\| `android_32_google_apis_x64_foldable.textpb` \| 12L (S_V2) \| Foldable Phone \| [android-12l-x64-dbg-tests][android-12l-x64-dbg-tests] \|
	\| `android_32_google_apis_x64_foldable_landscape.textpb` \| 12L (S_V2) \| Foldable Phone (Landscape) \| [android-12l-landscape-x64-dbg-tests][android-12l-landscape-x64-dbg-tests] \|
	\| `android_33_google_apis_x64.textpb` \| 13 (T) \| Phone \| [android-13-x64-rel][android-13-x64-rel] \|
	\| `android_34_google_apis_x64.textpb` \| 14 (U) \| Phone \| [android-14-x64-rel][android-14-x64-rel] \|
	\| `android_35_google_apis_x64.textpb` \| 15 (V) \| Phone \| [android-15-x64-rel][android-15-x64-rel] \|
	\| `android_35_google_apis_x64_tablet.textpb` \| 15 (V) \| Tablet \| [android-15-tablet-x64-dbg-tests][android-15-tablet-x64-dbg-tests] \|
	\| `android_35_google_apis_x64_tablet_landscape.textpb` \| 15 (V) \| Tablet (Landscape) \| [android-15-tablet-landscape-x64-dbg-tests][android-15-tablet-landscape-x64-dbg-tests] \|

	You can use these configuration files to run the same emulator images locally.

	[android-oreo-x86-rel]: https://ci.chromium.org/p/chromium/builders/ci/android-oreo-x86-rel
	[android-pie-x86-rel]: https://ci.chromium.org/p/chromium/builders/ci/android-pie-x86-rel
	[android-11-x86-rel]: https://ci.chromium.org/p/chromium/builders/ci/android-11-x86-rel
	[android-12-x64-rel]: https://ci.chromium.org/p/chromium/builders/ci/android-12-x64-rel
	[android-12l-x64-dbg-tests]: https://ci.chromium.org/p/chromium/builders/ci/android-12l-x64-dbg-tests
	[android-12l-landscape-x64-dbg-tests]: https://ci.chromium.org/p/chromium/builders/ci/android-12l-landscape-x64-dbg-tests
	[android-13-x64-rel]: https://ci.chromium.org/p/chromium/builders/ci/android-13-x64-rel
	[android-14-x64-rel]: https://ci.chromium.org/p/chromium/builders/ci/android-14-x64-rel
	[android-15-x64-rel]: https://ci.chromium.org/p/chromium/builders/ci/android-15-x64-rel
	[android-15-tablet-x64-dbg-tests]: https://ci.chromium.org/ui/p/chromium/builders/ci/android-15-tablet-x64-dbg-tests
	[android-15-tablet-landscape-x64-dbg-tests]: https://ci.chromium.org/ui/p/chromium/builders/ci/android-15-tablet-landscape-x64-dbg-tests

	> Note: New AVD configurations for LOCAL development are also available now,
	> whose file names end with `_local`, i.e. `*_local.textpb`.
	>
	> The only difference is that these configs has 12GB storage space instead of
	> 4GB on the non-local ones. Larger storage space makes it easier for developers
	> to install large APKs without hitting the space issue.

	#### Prerequisite

	* Make sure KVM (Kernel-based Virtual Machine) is enabled.
	See this
	[link](https://developer.android.com/studio/run/emulator-acceleration#vm-linux)
	from android studio for more details and instructions.

	* You need to have the permissions to use KVM.
	Use the following command to see if you are in group `kvm`:

	```
	$ grep kvm /etc/group
	```

	If your username is not shown in the group, add yourself to the group:

	```
	$ sudo adduser $USER kvm
	$ newgrp kvm
	```

	You need to log out and log back in so the new groups take effect.

	#### Running via the test runner

	The android test runner can run emulator instances on its own. In doing so, it
	starts the emulator instances, runs tests against them, and then shuts them
	down. This is how builders run the emulator.

	##### Options

	* `--avd-config`

	To have the test runner run an emulator instance, use `--avd-config`:

	```
	$ out/Debug/bin/run_base_unittests \
	--avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb
	```

	* `--emulator-count`

	The test runner will launch one instance by default. To have it run multiple
	instances, use `--emulator-count`:

	```
	$ out/Debug/bin/run_base_unittests \
	--avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
	--emulator-count 4
	```

	* `--emulator-enable-network`

	The test runner runs the emulator without network access by default. To have
	it run with network access, use `--emulator-enable-network`:

	```
	$ out/Debug/bin/run_base_unittests \
	--avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
	--emulator-enable-network
	```

	* `--emulator-window`

	The test runner runs the emulator in headless mode by default. To have it run
	with a window, use `--emulator-window`:

	```
	$ out/Debug/bin/run_base_unittests \
	--avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
	--emulator-window
	```

	#### Running standalone

	The test runner will set up and tear down the emulator on each invocation.
	To manage emulator lifetime independently, use `tools/android/avd/avd.py`.

	##### Options

	* `--avd-config`

	This behaves the same as it does for the test runner.

	```
	$ tools/android/avd/avd.py start \
	--avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb
	```

	> Note: `avd.py start` will start an emulator instance and then terminate.
	> To shut down the emulator, use `adb emu kill`.

	* `--enable-network`

	Like the test runner, `avd.py` runs the emulator without network access by
	default. To enable network access, use `--enable-network`:

	```
	$ tools/android/avd/avd.py start \
	--avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
	--enable-network
	```

	* `--emulator-window`

	Like the test runner, `avd.py` runs the emulator in headless mode by default.
	To have it run with a window, use `--emulator-window`:

	```
	$ tools/android/avd/avd.py start \
	--avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
	--emulator-window
	```

	* `--gpu-mode GPU_MODE`

	Override the mode of hardware OpenGL ES emulation indicated by the AVD.
	See "emulator -help-gpu" for a full list of modes.

	* `--no-read-only`

	`avd.py` runs the emulator in read-only mode by default. To run a modifiable
	emulator, use `--no-read-only`:

	```
	$ tools/android/avd/avd.py start \
	--avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
	--no-read-only
	```

	* `--wipe-data`

	Reset the /data partition to the factory defaults. This removes all user
	settings from the AVD.

	```
	$ tools/android/avd/avd.py start \
	--avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
	--wipe-data
	```

	* `--writable-system`

	Makes system & vendor image writable. It's necessary to run
	```
	adb root
	adb remount
	```
	after the emulator starts.

	* `--debug-tags`

	`avd.py` disables the emulator log by default. When this option is used,
	emulator log will be enabled. It is useful when the emulator cannot be
	launched correctly. See `emulator -help-debug-tags` for a full list of tags.
	Use `--debug-tags=all` if you want to output all logs (warning: it is quite
	verbose).

	```
	$ tools/android/avd/avd.py start \
	--avd-config tools/android/avd/proto/android_33_google_apis_x64.textpb \
	--debug-tags init,snapshot
	```

	### Using Your Own Emulator Image

	By far the easiest way to set up emulator images is to use Android Studio.
	If you don't have an [Android Studio project](android_studio.md) already, you
	can create a blank one to be able to reach the Virtual Device Manager screen.

	Refer to: https://developer.android.com/studio/run/managing-avds.html

	Where files live:
	* System partition images are stored within the sdk directory.
	* Emulator configs and data partition images are stored within
	`~/.android/avd/`.

	#### Creating an Image

	##### Choosing a Skin

	Choose a skin with a small screen for better performance (unless you care about
	testing large screens).

	##### Choosing an Image

	Android Studio's image labels roughly translate to the following:

	\| AVD "Target" \| Virtual Device Configuration tab \| GMS? \| Build Properties \|
	\| --- \| --- \| --- \| --- \|
	\| Google Play \| "Recommended" (the default tab) \| This has GMS \| `user`/`release-keys` \|
	\| Google APIs \| "x86 Images" \| This has GMS \| `userdebug`/`dev-keys` \|
	\| No label \| "x86 Images" \| AOSP image, does not have GMS \| `eng`/`test-keys` \|

	*** promo
	Tip: if you're not sure which to use, choose Google APIs under the **x86
	Images** tab in the Virtual Device Configuration wizard.
	***

	##### Configuration

	"Show Advanced Settings" > scroll down:
	* Set internal storage to 4000MB (component builds are really big).
	* Set SD card to 1000MB (our tests push a lot of files to /sdcard).

	##### Known Issues

	* Our test & installer scripts do not work with pre-MR1 Jelly Bean.
	* Component builds do not work on pre-KitKat (due to the OS having a max
	number of shared libraries).
	* Jelly Bean and KitKat images sometimes forget to mount /sdcard :(.
	* This causes tests to fail.
	* To ensure it's there: `adb -s emulator-5554 shell mount` (look for /sdcard)
	* Can often be fixed by editing `~/.android/avd/YOUR_DEVICE/config.ini`.
	* Look for `hw.sdCard=no` and set it to `yes`
	* The "Google APIs" Android L and M emulator images are configured to expect
	the "AOSP" WebView package (`com.android.webview`). This does not resemble
	production devices with GMS, which expect the ["Google WebView"
	configuration](/android_webview/docs/webview-providers.md#webview-provider-options)
	(`com.google.android.webview` on L and M). See [Removing preinstalled
	WebView](/android_webview/docs/build-instructions.md#Removing-preinstalled-WebView)
	if you need to install a local build or official build.


	#### Starting an Emulator from the Command Line

	Refer to: https://developer.android.com/studio/run/emulator-commandline.html.

	*** promo
	Ctrl-C will gracefully close an emulator.
	***

	*** promo
	Tip: zsh users can add https://github.com/zsh-users/zsh-completions to
	provide tab completion for the `emulator` command line tool.
	***

	#### Basic Command Line Use

	```shell
	$ # List virtual devices that you've created:
	$ ~/Android/Sdk/emulator/emulator -list-avds
	$ # Start a named device:
	$ ~/Android/Sdk/emulator/emulator @EMULATOR_ID
	```

	#### Running a Headless Emulator

	You can run an emulator without creating a window on your desktop (useful for
	`ssh`):
	```shell
	$ ~/Android/Sdk/emulator/emulator -no-window @EMULATOR_ID
	$ # This also works for new enough emulator builds:
	$ ~/Android/Sdk/emulator/emulator-headless @EMULATOR_ID
	```

	#### Running Multiple Emulators

	Tests are automatically sharded amongst available devices. If you run multiple
	emulators, then running test suites becomes much faster. Refer to the
	"Multiple AVD instances" section of these [emulator release notes](
	https://androidstudio.googleblog.com/2018/11/emulator-28016-stable.html)
	for more about how this works.
	```shell
	$ # Start 8 emulators. Press Ctrl-C to stop them all.
	$ ( for i in $(seq 8); do ~/Android/Sdk/emulator/emulator @EMULATOR_ID -read-only & done; wait )
	$ # Start 12 emulators. More than 10 requires disabling audio on some OS's. Reducing cores increases parallelism.
	$ ( for i in $(seq 12); do ~/Android/Sdk/emulator/emulator @EMULATOR_ID -read-only -no-audio -cores 2 & done; wait )
	```

	#### Writable system partition

	Unlike physical devices, an emulator's `/system` partition cannot be modified by
	default (even on rooted devices). If you need to do so (such as to remove a
	system app), you can start your emulator like so:
	```shell
	$ ~/Android/Sdk/emulator/emulator -writable-system @EMULATOR_ID
	```

	## Using an Emulator
	* Emulators show up just like devices via `adb devices`
	* Device serials will look like "emulator-5554", "emulator-5556", etc.

	## Emulator pros and cons

	### Pros
	* Compiles are faster. Many physical devices are arm64, whereas emulators
	are typically x86 (32-bit). 64-bit builds may require 2 copies of the native
	library (32-bit and 64-bit), so compiling for an arm64 phone is ~twice as
	much work as for an emulator (for targets which support WebView).
	* APKs install faster. Since emulators run on your workstation, adb can
	push the APK onto the emulator without being [bandwidth-constrained by
	USB](https://youtu.be/Mzop8bXZI3E).
	* Emulators can be nice for working remotely. Physical devices usually require
	`scp` or ssh port forwarding to copy the APK from your workstation and
	install on a local device. Emulators run on your workstation, so there's **no
	ssh slow-down**.

	### Cons
	* If you're investigating a hardware-specific bug report, you'll need a
	physical device with the actual hardware to repro that issue.
	* x86 emulators need a separate out directory, so building for both physical
	devices and emulators takes up more disk space (not a problem if you build
	exclusively for the emulator).
	* `userdebug`/`eng` emulators don't come with the Play Store installed, so you
	can't install third party applications. Sideloading is tricky, as not all
	third-party apps support x86.