Control the Emulator from the Command Line

The Android SDK includes a mobile device emulator — a virtual mobile device that runs on your computer. The emulator lets you develop and test Android applications without using a physical device.

This page describes command line features that you can use with the Android Emulator. For information about using the Android Emulator UI, see Using the Android Emulator.

Starting and Stopping the Emulator

During development and testing of your application, you install and run your application in the Android Emulator. You can launch the emulator as a standalone application from a command line, or you can run it from within your Android Studio development environment. In either case, you specify the AVD configuration to load and any startup options you want to use, as described in this document.

You can run your application on a single instance of the emulator or, depending on your needs, you can start multiple emulator instances and run your application in more than one emulated device. You can use the emulator built-in commands to simulate GSM phone calling or SMS between emulator instances, and you can set up network redirection that allows emulators to send data to one another. For more information, see Telephony Emulation, SMS Emulation, and Emulator Networking.

To start an instance of the emulator from the command line, navigate to the tools/ folder of the SDK. Enter emulator command like this:

emulator -avd <avd_name> [<options>]

This initializes the emulator, loads an AVD configuration and displays the emulator window.

Note: You can run multiple instances of the emulator concurrently, each with its own AVD configuration and storage area for user data, SD card, and so on.

When you run your app from Android Studio, it installs and launches the app on your connected device or emulator (launching the emulator, if necessary). You can specify emulator startup options in the Run/Debug dialog, in the Target tab. When the emulator is running, you can issue console commands as described later in this document.

If you are not working in Android Studio, see Installing Applications on the Emulator for information about how to install your application.

To stop an emulator instance, just close the emulator window.

emulator -avd <avd_name> [<options>]

Installing Applications on the Emulator

If you don't have access to Android Studio, you can install your application on the emulator using the adb utility. Before installing the application, you need to build and package it into an .apk as described in Build and Run Your App. After the application is installed, you can start the emulator from the command line as described previously, using any startup options necessary. When the emulator is running, you can also connect to the emulator console to issue commands as needed.

As you update your code, you periodically package and install it on the emulator. The emulator preserves the application and its state data across restarts, in a user-data disk partition. To ensure that the application runs properly as you update it, you may need to delete the emulator user-data partition. To do so, start the emulator with the -wipe-data option. For more information about the user-data partition and other emulator storage, see Working with Emulator Disk Images.

Using Command Line Parameters

The emulator supports a variety of options that you can specify when launching the emulator, to control its appearance or behavior. Here's the command-line syntax of the options available to the emulator program:

	emulator -avd <avd_name> [-<option> [<value>]] ... [-<qemu args>]
	

	emulator -list-avds
	

	emulator -avd <avd_name> [-<option> [<value>]] ... [-<qemu args>]
	

	emulator -list-avds
	

Using the Emulator Console

Each running emulator instance provides a console that lets you query and control the emulated device environment. For example, you can use the console to manage port redirection, network characteristics, and telephony events while your application is running on the emulator.

Starting and stopping a console session

To access the console and enter commands, from a terminal window, use telnet to connect to the console port and provide your authentication token. Each time the console displays OK, it's ready to accept commands. It doesn't have a typical prompt.

To connect to the console of a running emulator instance:

1. Open a terminal window and enter the following command:

telnet localhost console-port

The emulator window title lists the console port number. For example, the window title for an emulator using console port 5554 could be 5554:Nexus_5X_API_23.

An emulator instance occupies a pair of adjacent ports: a console port and an adb port. The port numbers differ by 1, with the adb port having the higher port number. The console of the first emulator instance running on a particular machine uses console port 5554 and adb port 5555. Subsequent instances use port numbers increasing by two — for example, 5556/5557, 5558/5559, and so on. Up to 16 concurrent emulator instances can run a console facility.

To connect to the emulator console, you must specify a valid console port. If multiple emulator instances are running, you need to determine the console port of the emulator instance you want to connect to.

The adb devices command prints a list of running emulator instances and their console port numbers. For more information, see Querying for Emulator/Device Instances.

Note: The emulator listens for connections on ports 5554 to 5587 and accepts connections from localhost only.

2. After the console displays OK, enter the auth auth_token command.

Before you can enter console commands, the emulator console requires authentication. auth_token must match the contents of the .emulator_console_auth_token file in your home directory.

If that file doesn't exist, the telnet localhost console-port command creates the file, which contains a randomly generated authentication token.

To disable authentication, delete the token from the .emulator_console_auth_token file or create an empty file if it doesn't exist.

3. After you're connected to the console, enter console commands.

Enter help and help command to see a list of console commands and learn about specific commands.

4. To exit the console session, enter quit or exit.

Here's an example session:

	me-macbook$ telnet localhost 5554
	Trying ::1...
	telnet: connect to address ::1: Connection refused
	Trying 127.0.0.1...
	Connected to localhost.
	Escape character is '^]'.
	Android Console: Authentication required
	Android Console: type 'auth <auth_token>' to authenticate
	Android Console: you can find your <auth_token> in
	'/Users/me/.emulator_console_auth_token'
	OK
	auth 123456789ABCdefZ
	Android Console: type 'help' for a list of commands
	OK
	help
	Android console command help:

	    help|h|?         print a list of commands
	    crash            crash the emulator instance
	    kill             kill the emulator instance
	    quit|exit        quit control session
	    redir            manage port redirections
	    power            power related commands
	    event            simulate hardware events
	    avd              control virtual device execution
	    finger           manage emulator fingerprint
	    geo              Geo-location commands
	    sms              SMS related commands
	    cdma             CDMA related commands
	    gsm              GSM related commands
	    rotate           rotate the screen by 90 degrees

	try 'help <command>' for command-specific help
	OK
	exit
	Connection closed by foreign host.
	me-macbook$
	

The following sections describe the major functional areas of the console.

	me-macbook$ telnet localhost 5554
	Trying ::1...
	telnet: connect to address ::1: Connection refused
	Trying 127.0.0.1...
	Connected to localhost.
	Escape character is '^]'.
	Android Console: Authentication required
	Android Console: type 'auth <auth_token>' to authenticate
	Android Console: you can find your <auth_token> in
	'/Users/me/.emulator_console_auth_token'
	OK
	auth 123456789ABCdefZ
	Android Console: type 'help' for a list of commands
	OK
	help
	Android console command help:

	    help|h|?         print a list of commands
	    crash            crash the emulator instance
	    kill             kill the emulator instance
	    quit|exit        quit control session
	    redir            manage port redirections
	    power            power related commands
	    event            simulate hardware events
	    avd              control virtual device execution
	    finger           manage emulator fingerprint
	    geo              Geo-location commands
	    sms              SMS related commands
	    cdma             CDMA related commands
	    gsm              GSM related commands
	    rotate           rotate the screen by 90 degrees

	try 'help <command>' for command-specific help
	OK
	exit
	Connection closed by foreign host.
	me-macbook$
	

Port redirection

You can use the console to add and remove port redirection while the emulator is running. After you connect to the console, manage port redirection by entering the following command:

redir <list|add|del> 

The redir command supports the subcommands listed in the table below.

redir <list|add|del> 

Geo location provider emulation

You can use the console to set the geographic location reported to the applications running inside an emulator. Use the geo command to send a simple GPS fix to the emulator, with or without NMEA 1083 formatting:

geo <fix|nmea>

The geo command supports the subcommands listed in the table below.

You can issue the geo command as soon as an emulator instance is running. The emulator sets the location you enter by creating a mock location provider. This provider responds to location listeners set by applications, and also supplies the location to the LocationManager. Any application can query the location manager to obtain the current GPS fix for the emulated device by calling:

LocationManager.getLastKnownLocation("gps")

For more information about the Location Manager, see LocationManager.

geo <fix|nmea>

LocationManager.getLastKnownLocation("gps")

Hardware events emulation

The event console commands sends hardware events to the emulator. The syntax for this command is as follows:

event <send|types|codes|text>

The event command supports the subcommands listed in the table below.

event <send|types|codes|text>

Device power characteristics

The power command controls the power state reported by the emulator to applications. The syntax for this command is as follows:

power <display|ac|status|present|health|capacity>

The event command supports the subcommands listed in the table below.

power <display|ac|status|present|health|capacity>

Network status

You can use the console to check the network status and current delay and speed characteristics. To do so, connect to the console and use the netstatus command. Here's an example of the command and its output.

network status
	

network status
	

Network delay emulation

The emulator lets you simulate various network latency levels, so that you can test your application in an environment more typical of the actual conditions in which it will run. You can set a latency level or range at emulator startup or you can use the console to change the latency, while the application is running in the emulator.

To set latency at emulator startup, use the -netdelay emulator option with a supported <delay> value, as listed in the table below. Here are some examples:

emulator -netdelay gprs
	emulator -netdelay 40 100

To make changes to network delay while the emulator is running, connect to the console and use the netdelay command with a supported <delay> value from the table below.

network delay gprs

The format of network <delay> is one of the following (numbers are milliseconds):

emulator -netdelay gprs
	emulator -netdelay 40 100

network delay gprs

Network speed emulation

The emulator also lets you simulate various network transfer rates. You can set a transfer rate or range at emulator startup or you can use the console to change the rate, while the application is running in the emulator.

To set the network speed at emulator startup, use the -netspeed emulator option with a supported <speed> value, as listed in the table below. Here are some examples:

emulator -netspeed gsm
	emulator -netspeed 14.4 80

To make changes to network speed while the emulator is running, connect to the console and use the netspeed command with a supported <speed> value from the table below.

network speed 14.4 80

The format of network <speed> is one of the following (numbers are kilobits/sec):

emulator -netspeed gsm
	emulator -netspeed 14.4 80

network speed 14.4 80

Telephony emulation

The Android emulator includes its own GSM emulated modem that lets you simulate telephony functions in the emulator. For example, you can simulate inbound phone calls, establish data connections and terminate them. The Android system handles simulated calls exactly as it would actual calls. The emulator does not support call audio.

You can use the gsm command to access the emulator telephony functions after connecting to the console. The syntax for this command is as follows:

gsm <call|accept|busy|cancel|data|hold|list|voice|status> 

The gsm command supports the subcommands listed in the table below.

gsm <call|accept|busy|cancel|data|hold|list|voice|status> 

SMS emulation

The Android emulator console lets you generate an SMS message and direct it to an emulator instance. Once you connect to an emulator instance, you can generate an emulated incoming SMS using the following command:

sms send <senderPhoneNumber> <textmessage>

where <senderPhoneNumber> contains an arbitrary numeric string.

The console forwards the SMS message to the Android framework, which passes it through to an application that handles that message type.

sms send <senderPhoneNumber> <textmessage>

VM state

You can use the vm command to control the VM on an emulator instance. The syntax for this command is as follows:

vm <start|stop|status>

The vm command supports the subcommands listed in the table below.

vm <start|stop|status>

Emulator window

You can use the window command to manage the emulator window. The syntax for this command is as follows:

window <scale>

The vm command supports the subcommands listed in the table below.

window <scale>

Simulating finger print support

Android Emulator console provides the finger command, allowing you to simulate, and thus validate, finger print authentication for your app. After you set up your app to accept finger print authentication, your emulator or device should display the finger print authentication screen, as shown in figure 1.

Figure 1. The finger print authentication screen.

Open a terminal session, and telnet to the emulator. For example:

	telnet localhost 5554
	

Enter the finger command to simulate finger touch and removal:

• finger touch <fingerprint-id> to simulate a finger touching the sensor
• finger remove to simulate finger removal

Your app should respond as if a user touched and then removed their finger from the finger print sensor.

Simulating finger print support Android Emulator console provides the finger command, allowing you to simulate, and thus validate, finger print authentication for your app. After you set up your app to accept finger print authentication, your emulator or device should display the finger print authentication screen, as shown in figure 1. Figure 1. The finger print authentication screen. Open a terminal session, and telnet to the emulator. For example: telnet localhost 5554 Enter the finger command to simulate finger touch and removal: finger touch <fingerprint-id> to simulate a finger touching the sensor finger remove to simulate finger removal Your app should respond as if a user touched and then removed their finger from the finger print sensor.

Terminating an emulator instance

You can terminate an emulator instance through the console, using the kill command.

Using SD Card Emulation

You can create a disk image and then load it to the emulator at startup, to simulate the presence of a user's SD card in the device. To do this, you can specify an SD card image when you create an AVD, or you can use the mksdcard utility included in the SDK.

The following sections describe how to create an SD card disk image, how to copy files to it, and how to load it in the emulator at startup.

Note that you can only load a disk image at emulator startup. Similarly, you can not remove a simulated SD card from a running emulator. However, you can browse, send files to, and copy/remove files from a simulated SD card either with adb or the emulator.

The emulator supports emulated SDHC cards, so you can create an SD card image of any size up to 128 gigabytes.

Creating an SD card image

There are several ways of creating an SD card image. The easiest way is to use the AVD Manager to create a new SD card by specifying a size when you create an AVD.

You can also use the mksdcard tool, included in the SDK, to create a FAT32 disk image that you can load in the emulator at startup. You can access mksdcard in the tools directory of the SDK and create a disk image like this:

mksdcard <size> <file>

For example:

mksdcard 1024M sdcard1.iso

For more information, see mksdcard.

mksdcard <size> <file>

mksdcard 1024M sdcard1.iso

Copying files to an SD card image

Once you have created the disk image, you can copy files to it prior to loading it in the emulator. To copy files, you can mount the image as a loop device and then copy the files to it, or you can use a utility such as mtools to copy the files directly to the image. The mtools package is available for Linux, Mac, and Windows.

Alternatively, you can use the adb push command to move files onto an SD card image while it is loaded in an emulator. For more information see the adb push documentation.

Loading an SD card image

By default, the emulator loads the SD card image that is stored with the active AVD (see the -avd startup option).

Alternatively, you can start the emulator with the -sdcard flag and specify the name and path of your image (relative to the current working directory):

emulator -sdcard <filepath>

emulator -sdcard <filepath>

Working with Emulator Disk Images

The emulator uses mountable disk images stored on your development machine to simulate flash (or similar) partitions on an actual device. For example, it uses a disk image containing an emulator-specific kernel, the Android system, a ramdisk image, and writable images for user data and simulated SD card.

To run properly, the emulator requires access to a specific set of disk image files. By default, the Emulator always looks for the disk images in the private storage area of the AVD in use. If no images exist there when the Emulator is launched, it creates the images in the AVD directory based on default versions stored in the SDK.

Note: The default storage location for AVDs is in ~/.android/avd on OS X and Linux, C:\Documents and Settings\<user>\.android\ on Windows XP, and C:\Users\<user>\.android\ on Windows Vista.

To let you use alternate or custom versions of the image files, the emulator provides startup options that override the default locations and filenames of the image files. When you use one of these options, the emulator searches for the image file under the image name or location that you specify; if it can not locate the image, it reverts to using the default names and location.

The emulator uses three types of image files: default image files, runtime image files, and temporary image files. The sections below describe how to override the location/name of each type of file.

Default image files

When the emulator launches, but does not find an existing user data image in the active AVD storage area, it creates a new one from a default version included in the SDK. The default user data image is read-only. The image files are read-only.

The emulator provides the -system <dir> startup option to let you override the location where the emulator looks for the default user data image.

The emulator also provides a startup option that lets you override the name of the default user data image, as described in the following table. When you use the option, the emulator looks in the default directory, or in a custom location (if you specified -system <dir>).

Runtime images: user data and SD card

At runtime, the emulator reads and writes data to two disk images: a user-data image and (optionally) an SD card image. These images emulate the user-data partition and removable storage media on actual device.

The emulator provides a default user-data disk image. At startup, the emulator creates the default image as a copy of the system user-data image (user-data.img), described above. The emulator stores the new image with the files of the active AVD.

The emulator provides startup options to let you override the actual names and storage locations of the runtime images to load, as described in the following table. When you use one of these options, the emulator looks for the specified file(s) in the current working directory, in the AVD directory, or in a custom location (if you specified a path with the filename).

User-data image

Each emulator instance uses a writable user-data image to store user- and session-specific data. For example, it uses the image to store a unique user's installed application data, settings, databases, and files.

At startup, the emulator attempts to load a user-data image stored during a previous session. It looks for the file in the current working directory, in the AVD directory described in a previous section and at the custom location/name that you specified at startup.

• If it finds a user-data image, it mounts the image and makes it available to the system for reading and writing of user data.
• If it does not find one, it creates an image by copying the system user-data image (userdata.img), described above. At device power-off, the system persists the user data to the image, so that it will be available in the next session. Note that the emulator stores the new disk image at the location/name that you specify in -data startup option.

Note: Because of the AVD configurations used in the emulator, each emulator instance gets its own dedicated storage. There is no longer a need to use the -d option to specify an instance-specific storage area.

SD card

Optionally, you can create a writable disk image that the emulator can use to simulate removeable storage in an actual device. For information about how to create an emulated SD card and load it in the emulator, see Using SD Card Emulation.

You can also use the android tool to automatically create an SD Card image for you, when creating an AVD. For more information, see Managing AVDs with the AVD Manager.

Temporary images

The emulator creates two writable images at startup that it deletes at device power-off. The images are:

• A writable copy of the Android system image
• The /cache partition image

The emulator does not permit renaming the temporary system image or persisting it at device power-off.

The /cache partition image is initially empty, and is used by the browser to cache downloaded web pages and images. The emulator provides an -cache <file>, which specifies the name of the file in which to persist the /cache image at device power-off. If <file> does not exist, the emulator creates it as an empty file.

You can also disable the use of the cache partition by specifying the -nocache option at startup.

Setting Up Emulator Networking

The emulator provides versatile networking capabilities that you can use to set up complex modeling and testing environments for your application. The sections below introduce the emulator network architecture and capabilities.

Network address space

Each instance of the emulator runs behind a virtual router/firewall service that isolates it from your development machine network interfaces and settings and from the internet. An emulated device can not see your development machine or other emulator instances on the network. Instead, it sees only that it is connected through Ethernet to a router/firewall.

The virtual router for each instance manages the 10.0.2/24 network address space — all addresses managed by the router are in the form of 10.0.2.<xx>, where <xx> is a number. Addresses within this space are pre-allocated by the emulator/router as follows:

Note that the same address assignments are used by all running emulator instances. That means that if you have two instances running concurrently on your machine, each will have its own router and, behind that, each will have an IP address of 10.0.2.15. The instances are isolated by a router and can not see each other on the same network. For information about how to let emulator instances communicate over TCP/UDP, see Interconnecting Emulator Instances.

Also note that the address 127.0.0.1 on your development machine corresponds to the emulator own loopback interface. If you want to access services running on your development machine loopback interface (a.k.a. 127.0.0.1 on your machine), you should use the special address 10.0.2.2 instead.

Finally, note that the pre-allocated addresses of an emulated devider are specific to the Android Emulator and will probably be very different on real devices (which are also very likely to be NAT-ed, specifically, behind a router/firewall).

Local networking limitations

Android applications running in an emulator can connect to the network available on your workstation. However, they connect through the emulator, not directly to hardware, and the emulator acts like a normal application on your workstation. This means that the emulator, and thus your Android applications, are subject to some limitations:

• Communication with the emulated device may be blocked by a firewall program running on your machine.
• Communication with the emulated device may be blocked by another (physical) firewall/router to which your machine is connected.

The emulator virtual router should be able to handle all outbound TCP and UDP connections/messages on behalf of the emulated device, provided your development machine network environment allows it to do so. There are no built-in limitations on port numbers or ranges except the one imposed by your host operating system and network.

Depending on the environment, the emulator may not be able to support other protocols (such as ICMP, used for "ping") might not be supported. Currently, the emulator does not support IGMP or multicast.

Using network redirection

To communicate with an emulator instance behind its virtual router, you need to set up network redirection on the virtual router. Clients can then connect to a specified guest port on the router, while the router directs traffic to/from that port to the emulated device host port.

To set up the network redirection, you create a mapping of host and guest ports/addresses on the emulator instance. There are two ways to set up network redirection: using emulator console commands and using the adb tool, as described below.

Setting up redirection through the Emulator Console

Each emulator instance provides a control console the you can connect to, to issue commands that are specific to that instance. You can use the redir console command to set up redirection as needed for an emulator instance.

First, determine the console port number for the target emulator instance. For example, the console port number for the first emulator instance launched is 5554. Next, connect to the console of the target emulator instance, specifying its console port number, as follows:

telnet localhost 5554

Once connected, use the redir command to work with redirection. To add a redirection, use:

add <protocol>:<host-port>:<guest-port>

where <protocol> is either tcp or udp, and <host-port> and <guest-port> sets the mapping between your own machine and the emulated system, respectively.

For example, the following command sets up a redirection that handles all incoming TCP connections to your host (development) machine on 127.0.0.1:5000 and will pass them through to the emulated system 10.0.2.15:6000:

redir add tcp:5000:6000

To delete a redirection, you can use the redir del command. To list all redirection for a specific instance, you can use redir list. For more information about these and other console commands, see Using the Emulator Console.

Note that port numbers are restricted by your local environment. this typically means that you cannot use host port numbers under 1024 without special administrator privileges. Also, you won't be able to set up a redirection for a host port that is already in use by another process on your machine. In that case, redir generates an error message to that effect.

telnet localhost 5554

add <protocol>:<host-port>:<guest-port>

redir add tcp:5000:6000

Setting up redirection through adb

The Android Debug Bridge (adb) tool provides port forwarding, an alternate way for you to set up network redirection. For more information, see Forwarding Ports in the adb documentation.

Note that adb does not currently offer any way to remove a redirection, except by killing the adb server.

Configuring the emulator DNS settings

At startup, the emulator reads the list of DNS servers that your system is currently using. It then stores the IP addresses of up to four servers on this list and sets up aliases to them on the emulated addresses 10.0.2.3, 10.0.2.4, 10.0.2.5 and 10.0.2.6 as needed.

On Linux and OS X, the emulator obtains the DNS server addresses by parsing the file /etc/resolv.conf. On Windows, the emulator obtains the addresses by calling the GetNetworkParams() API. Note that this usually means that the emulator ignores the content of your "hosts" file (/etc/hosts on Linux/OS X, %WINDOWS%/system32/HOSTS on Windows).

When starting the emulator at the command line, you can also use the -dns-server <serverList> option to manually specify the addresses of DNS servers to use, where <serverList> is a comma-separated list of server names or IP addresses. You might find this option useful if you encounter DNS resolution problems in the emulated network (for example, an "Unknown Host error" message that appears when using the web browser).

Using the emulator with a proxy

If your emulator must access the Internet through a proxy server, you can use the -http-proxy <proxy> option when starting the emulator, to set up the appropriate redirection. In this case, you specify proxy information in <proxy> in one of these formats:

http://<machineName>:<port>

or

http://<username>:<password>@<machineName>:<port>

The -http-proxy option forces the emulator to use the specified HTTP/HTTPS proxy for all outgoing TCP connections. Redirection for UDP is not currently supported.

Alternatively, you can define the environment variable http_proxy to the value you want to use for <proxy>. In this case, you do not need to specify a value for <proxy> in the -http-proxy command — the emulator checks the value of the http_proxy environment variable at startup and uses its value automatically, if defined.

You can use the -verbose-proxy option to diagnose proxy connection problems.

http://<machineName>:<port>

http://<username>:<password>@<machineName>:<port>

Interconnecting emulator instances

To allow one emulator instance to communicate with another, you must set up the necessary network redirection as illustrated below.

Assume that your environment is

• A is you development machine
• B is your first emulator instance, running on A
• C is your second emulator instance, also running on A

and you want to run a server on B, to which C will connect, here is how you could set it up:

1. Set up the server on B, listening to 10.0.2.15:<serverPort>
2. On the B console, set up a redirection from A:localhost:<localPort> to B:10.0.2.15:<serverPort>
3. On C, have the client connect to 10.0.2.2:<localPort>

For example, if you wanted to run an HTTP server, you can select <serverPort> as 80 and <localPort> as 8080:

• B listens on 10.0.2.15:80
• On the B console, issue redir add tcp:8080:80
• C connects to 10.0.2.2:8080

Sending a voice call or SMS to another emulator instance

The emulator automatically forwards simulated voice calls and SMS messages from one instance to another. To send a voice call or SMS, use the dialer application or SMS application, respectively, from one of the emulators.

To initiate a simulated voice call to another emulator instance:

1. Launch the dialer application on the originating emulator instance.
2. As the number to dial, enter the console port number of the instance you'd like to call. You can determine the console port number of the target instance by checking its window title, where the console port number is reported as "Android Emulator (<port>).
3. Press "Dial". A new inbound call appears in the target emulator instance.

To send an SMS message to another emulator instance, launch the SMS application (if available). Specify the console port number of the target emulator instance as as the SMS address, enter the message text, and send the message. The message is delivered to the target emulator instance.

You can also connect to an emulator console to simulate an incoming voice call or SMS. For more information, see Telephony Emulation and SMS Emulation.

Troubleshooting Emulator Problems

The adb utility sees the emulator as an actual physical device. For this reason, you might have to use the -d flag with some common adb commands, such as install. The -d flag lets you specify which of several connected devices to use as the target of a command. If you don't specify -d, the emulator targets the first device in its list. For more information about adb, see Android Debug Bridge.

For emulators running on Mac OS X, if you see an error Warning: No DNS servers found when starting the emulator, check to see whether you have an /etc/resolv.conf file. If not, please run the following line in a command window:

ln -s /private/var/run/resolv.conf /etc/resolv.conf

ln -s /private/var/run/resolv.conf /etc/resolv.conf