Overview ======== A :class:`Target` instance serves as the main interface to the target device. There currently three target interfaces: - :class:`LinuxTarget` for interacting with Linux devices over SSH. - :class:`AndroidTraget` for interacting with Android devices over adb. - :class:`LocalLinuxTarget`: for interacting with the local Linux host. They all work in more-or-less the same way, with the major difference being in how connection settings are specified; though there may also be a few APIs specific to a particular target type (e.g. :class:`AndroidTarget` exposes methods for working with logcat). Acquiring a Target ------------------ To create an interface to your device, you just need to instantiate one of the :class:`Target` derivatives listed above, and pass it the right ``connection_settings``. Code snippet below gives a typical example of instantiating each of the three target types. .. code:: python from devlib import LocalLinuxTarget, LinuxTarget, AndroidTarget # Local machine requires no special connection settings. t1 = LocalLinuxTarget() # For a Linux device, you will need to provide the normal SSH credentials. # Both password-based, and key-based authentication is supported (password # authentication requires sshpass to be installed on your host machine).' t2 = LinuxTarget(connetion_settings={'host': '192.168.0.5', 'username': 'root', 'password': 'sekrit', # or 'keyfile': '/home/me/.ssh/id_rsa'}) # For an Android target, you will need to pass the device name as reported # by "adb devices". If there is only one device visible to adb, you can omit # this setting and instantiate similar to a local target. t3 = AndroidTarget(connection_settings={'device': '0123456789abcde'}) Instantiating a target may take a second or two as the remote device will be queried to initialize :class:`Target`'s internal state. If you would like to create a :class:`Target` instance but not immediately connect to the remote device, you can pass ``connect=False`` parameter. If you do that, you would have to then explicitly call ``t.connect()`` before you can interact with the device. There are a few additional parameters you can pass in instantiation besides ``connection_settings``, but they are usually unnecessary. Please see :class:`Target` API documentation for more details. Target Interface ---------------- This is a quick overview of the basic interface to the device. See :class:`Targeet` API documentation for the full list of supported methods and more detailed documentation. One-time Setup ~~~~~~~~~~~~~~ .. code:: python from devlib import LocalLinuxTarget t = LocalLinuxTarget() t.setup() This sets up the target for ``devlib`` interaction. This includes creating working directories, deploying busybox, etc. It's usually enough to do this once for a new device, as the changes this makes will persist across reboots. However, there is no issue with calling this multiple times, so, to be on the safe site, it's a good idea to call this once at the beginning of your scripts. Command Execution ~~~~~~~~~~~~~~~~~ There are several ways to execute a command on the target. In each case, a :class:`TargetError` will be raised if something goes wrong. In very case, it is also possible to specify ``as_root=True`` if the specified command should be executed as root. .. code:: python from devlib import LocalLinuxTarget t = LocalLinuxTarget() # Execute a command output = t.execute('echo $PWD') # Execute command via a subprocess and return the corresponding Popen object. # This will block current connection to the device until the command # completes. p = t.background('echo $PWD') output, error = p.communicate() # Run the command in the background on the device and return immediately. # This will not block the connection, allowing to immediately execute another # command. t.kick_off('echo $PWD') # This is used to invoke an executable binary on the device. This allows some # finer-grained control over the invocation, such as specifying the directory # in which the executable will run; however you're limited to a single binary # and cannot construct complex commands (e.g. this does not allow chaining or # piping several commands together). output = t.invoke('echo', args=['$PWD'], in_directory='/') File Transfer ~~~~~~~~~~~~~ .. code:: python from devlib import LocalLinuxTarget t = LocalLinuxTarget() # "push" a file from the local machine onto the target device. t.push('/path/to/local/file.txt', '/path/to/target/file.txt') # "pull" a file from the target device into a location on the local machine t.pull('/path/to/target/file.txt', '/path/to/local/file.txt') # Install the specified binary on the target. This will deploy the file and # ensure it's executable. This will *not* guarantee that the binary will be # in PATH. Instead the path to the binary will be returned; this should be # used to call the binary henceforth. target_bin = t.install('/path/to/local/bin.exe') # Example invocation: output = t.execute('{} --some-option'.format(target_bin)) The usual access permission constraints on the user account (both on the target and the host) apply. Process Control ~~~~~~~~~~~~~~~ .. code:: python import signal from devlib import LocalLinuxTarget t = LocalLinuxTarget() # return PIDs of all running instances of a process pids = t.get_pids_of('sshd') # kill a running process. This works the same ways as the kill command, so # SIGTERM will be used by default. t.kill(666, signal=signal.SIGKILL) # kill all running instances of a process. t.killall('badexe', signal=signal.SIGKILL) # List processes running on the target. This retruns a list of parsed # PsEntry records. entries = t.ps() # e.g. print virtual memory sizes of all running sshd processes: print ', '.join(str(e.vsize) for e in entries if e.name == 'sshd') More... ~~~~~~~ As mentioned previously, the above is not intended to be exhaustive documentation of the :class:`Target` interface. Please refer to the API documentation for the full list of attributes and methods and their parameters. Super User Privileges --------------------- It is not necessary for the account logged in on the target to have super user privileges, however the functionality will obviously be diminished, if that is not the case. ``devilib`` will determine if the logged in user has root privileges and the correct way to invoke it. You should avoid including "sudo" directly in your commands, instead, specify ``as_root=True`` where needed. This will make your scripts portable across multiple devices and OS's. On-Target Locations ------------------- File system layouts vary wildly between devices and operating systems. Hard-coding absolute paths in your scripts will mean there is a good chance they will break if run on a different device. To help with this, ``devlib`` defines a couple of "standard" locations and a means of working with them. working_directory This is a directory on the target readable and writable by the account used to log in. This should generally be used for all output generated by your script on the device and as the destination for all host-to-target file transfers. It may or may not permit execution so executables should not be run directly from here. executables_directory This directory allows execution. This will be used by ``install()``. .. code:: python from devlib import LocalLinuxTarget t = LocalLinuxTarget() # t.path is equivalent to Python standard library's os.path, and should be # used in the same way. This insures that your scripts are portable across # both target and host OS variations. e.g. on_target_path = t.path.join(t.working_directory, 'assets.tar.gz') t.push('/local/path/to/assets.tar.gz', on_target_path) # Since working_directory is a common base path for on-target locations, # there a short-hand for the above: t.push('/local/path/to/assets.tar.gz', t.get_workpath('assets.tar.gz')) Modules ------- Additional functionality is exposed via modules. Modules are initialized as attributes of a target instance. By default, ``hotplug``, ``cpufreq``, ``cpuidle``, ``cgroups`` and ``hwmon`` will attempt to load on target; additional modules may be specified when creating a :class:`Target` instance. A module will probe the target for support before attempting to load. So if the underlying platform does not support particular functionality (e.g. the kernel on target device was built without hotplug support). To check whether a module has been successfully installed on a target, you can use ``has()`` method, e.g. .. code:: python from devlib import LocalLinuxTarget t = LocalLinuxTarget() cpu0_freqs = [] if t.has('cpufreq'): cpu0_freqs = t.cpufreq.list_frequencies(0) Please see the modules documentation for more detail. Measurement and Trace --------------------- You can collected traces (currently, just ftrace) using :class:`TraceCollector`\ s. For example .. code:: python from devlib import AndroidTarget, FtraceCollector t = LocalLinuxTarget() # Initialize a collector specifying the events you want to collect and # the buffer size to be used. trace = FtraceCollector(t, events=['power*'], buffer_size=40000) # clear ftrace buffer trace.reset() # start trace collection trace.start() # Perform the operations you want to trace here... import time; time.sleep(5) # stop trace collection trace.stop() # extract the trace file from the target into a local file trace.get_trace('/tmp/trace.bin') # View trace file using Kernelshark (must be installed on the host). trace.view('/tmp/trace.bin') # Convert binary trace into text format. This would normally be done # automatically during get_trace(), unless autoreport is set to False during # instantiation of the trace collector. trace.report('/tmp/trace.bin', '/tmp/trace.txt') In a similar way, :class:`Instrument` instances may be used to collect measurements (such as power) from targets that support it. Please see instruments documentation for more details.