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<chapter id='dev-manual-qemu'>

<title>Using the Quick EMUlator (QEMU)</title>

    <para>
        This chapter provides procedures that show you how to use the
        Quick EMUlator (QEMU), which is an Open Source project the Yocto
        Project uses as part of its development "tool set".
        For reference information on the Yocto Project implementation of QEMU,
        see the
        "<ulink url='&YOCTO_DOCS_REF_URL;#ref-quick-emulator-qemu'>Quick EMUlator (QEMU)</ulink>"
        section in the Yocto Project Reference Manual.
    </para>

    <section id='qemu-running-qemu'>
        <title>Running QEMU</title>

        <para>
            To use QEMU, you need to have QEMU installed and initialized as
            well as have the proper artifacts (i.e. image files and root
            filesystems) available.
            Follow these general steps to run QEMU:
            <orderedlist>
                <listitem><para>
                    <emphasis>Install QEMU:</emphasis>
                    See
                    "<ulink url='&YOCTO_DOCS_SDK_URL;#the-qemu-emulator'>The QEMU Emulator</ulink>"
                    section in the Yocto Project Application Development and
                    the Extensible Software Development Kit (eSDK) manual
                    for information on how to install QEMU.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Setting Up the Environment:</emphasis>
                    How you set up the QEMU environment depends on how you
                    installed QEMU:
                    <itemizedlist>
                        <listitem><para>
                            If you cloned the <filename>poky</filename>
                            repository or you downloaded and unpacked a
                            Yocto Project release tarball, you can source
                            the build environment script (i.e.
                            <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink>):
                            <literallayout class='monospaced'>
     $ cd ~/poky
     $ source oe-init-build-env
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            If you installed a cross-toolchain, you can
                            run the script that initializes the toolchain.
                            For example, the following commands run the
                            initialization script from the default
                            <filename>poky_sdk</filename> directory:
                            <literallayout class='monospaced'>
     . ~/poky_sdk/environment-setup-core2-64-poky-linux
                            </literallayout>
                            </para></listitem>
                    </itemizedlist>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Ensure the Artifacts are in Place:</emphasis>
                    You need to be sure you have a pre-built kernel that
                    will boot in QEMU.
                    You also need the target root filesystem for your target
                    machine’s architecture:
                    <itemizedlist>
                        <listitem><para>
                            If you have previously built an image for QEMU
                            (e.g. <filename>qemux86</filename>,
                            <filename>qemuarm</filename>, and so forth),
                            then the artifacts are in place in your
                            <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>.
                            </para></listitem>
                        <listitem><para>
                            If you have not built an image, you can go to the
                            <ulink url='&YOCTO_MACHINES_DL_URL;'>machines/qemu</ulink>
                            area and download a pre-built image that matches
                            your architecture and can be run on QEMU.
                            </para></listitem>
                    </itemizedlist></para>

                    <para>See the
                    "<ulink url='&YOCTO_DOCS_SDK_URL;#sdk-extracting-the-root-filesystem'>Extracting the Root Filesystem</ulink>"
                    section in the Yocto Project Application Development and
                    the Extensible Software Development Kit (eSDK) manual
                    for information on how to extract a root filesystem.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Run QEMU:</emphasis>
                    The basic <filename>runqemu</filename> command syntax is as
                    follows:
                    <literallayout class='monospaced'>
     $ runqemu [<replaceable>option</replaceable> ]  [...]
                    </literallayout>
                    Based on what you provide on the command line,
                    <filename>runqemu</filename> does a good job of figuring
                    out what you are trying to do.
                    For example, by default, QEMU looks for the most recently
                    built image according to the timestamp when it needs to
                    look for an image.
                    Minimally, through the use of options, you must provide
                    either a machine name, a virtual machine image
                    (<filename>*wic.vmdk</filename>), or a kernel image
                    (<filename>*.bin</filename>).</para>

                    <para>Here are some additional examples to help illustrate
                    further QEMU:
                    <itemizedlist>
                        <listitem><para>
                            This example starts QEMU with
                            <replaceable>MACHINE</replaceable> set to "qemux86".
                            Assuming a standard
                            <ulink url='&YOCTO_DOCS_REF_URL;#build-directory'>Build Directory</ulink>,
                            <filename>runqemu</filename> automatically finds the
                            <filename>bzImage-qemux86.bin</filename> image file and
                            the
                            <filename>core-image-minimal-qemux86-20140707074611.rootfs.ext3</filename>
                            (assuming the current build created a
                            <filename>core-image-minimal</filename> image).
                            <note>
                            When more than one image with the same name exists, QEMU finds
                            and uses the most recently built image according to the
                            timestamp.
                            </note>
                            <literallayout class='monospaced'>
     $ runqemu qemux86
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            This example produces the exact same results as the
                            previous example.
                            This command, however, specifically provides the image
                            and root filesystem type.
                            <literallayout class='monospaced'>
     $ runqemu qemux86 core-image-minimal ext3
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            This example specifies to boot an initial RAM disk image
                            and to enable audio in QEMU.
                            For this case, <filename>runqemu</filename> set the
                            internal variable <filename>FSTYPE</filename> to
                            "cpio.gz".
                            Also, for audio to be enabled, an appropriate driver must
                            be installed (see the previous description for the
                            <filename>audio</filename> option for more information).
                            <literallayout class='monospaced'>
     $ runqemu qemux86 ramfs audio
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            This example does not provide enough information for
                            QEMU to launch.
                            While the command does provide a root filesystem type, it
                            must also minimally provide a
                            <replaceable>MACHINE</replaceable>,
                            <replaceable>KERNEL</replaceable>, or
                            <replaceable>VM</replaceable> option.
                            <literallayout class='monospaced'>
     $ runqemu ext3
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            This example specifies to boot a virtual machine
                            image (<filename>.wic.vmdk</filename> file).
                            From the <filename>.wic.vmdk</filename>,
                            <filename>runqemu</filename> determines the QEMU
                            architecture (<replaceable>MACHINE</replaceable>) to be
                            "qemux86" and the root filesystem type to be "vmdk".
                            <literallayout class='monospaced'>
     $ runqemu /home/scott-lenovo/vm/core-image-minimal-qemux86.wic.vmdk
                            </literallayout>
                            </para></listitem>
                    </itemizedlist>
                    </para></listitem>
            </orderedlist>
        </para>
    </section>

    <section id='switching-between-consoles'>
        <title>Switching Between Consoles</title>

        <para>
            When booting or running QEMU, you can switch between
            supported consoles by using
            Ctrl+Alt+<replaceable>number</replaceable>.
            For example, Ctrl+Alt+3 switches you to the serial console
            as long as that console is enabled.
            Being able to switch consoles is helpful, for example, if
            the main QEMU console breaks for some reason.
            <note>
                Usually, "2" gets you to the main console and "3"
                gets you to the serial console.
            </note>
        </para>
    </section>

    <section id='removing-the-splash-screen'>
        <title>Removing the Splash Screen</title>

        <para>
            You can remove the splash screen when QEMU is booting by
            using Alt+left.
            Removing the splash screen allows you to see what is
            happening in the background.
        </para>
    </section>

    <section id='disabling-the-cursor-grab'>
        <title>Disabling the Cursor Grab</title>

        <para>
            The default QEMU integration captures the cursor within the
            main window.
            It does this since standard mouse devices only provide
            relative input and not absolute coordinates.
            You then have to break out of the grab using the "Ctrl+Alt"
            key combination.
            However, the Yocto Project's integration of QEMU enables
            the wacom USB touch pad driver by default to allow input
            of absolute coordinates.
            This default means that the mouse can enter and leave the
            main window without the grab taking effect leading to a
            better user experience.
        </para>
    </section>

    <section id='qemu-running-under-a-network-file-system-nfs-server'>
        <title>Running Under a Network File System (NFS) Server</title>

        <para>
            One method for running QEMU is to run it on an NFS server.
            This is useful when you need to access the same file system
            from both the build and the emulated system at the same time.
            It is also worth noting that the system does not need root
            privileges to run.
            It uses a user space NFS server to avoid that.
            Follow these steps to set up for running QEMU using an NFS
            server.
            <orderedlist>
                <listitem><para>
                    <emphasis>Extract a Root Filesystem:</emphasis>
                    Once you are able to run QEMU in your environment, you can
                    use the <filename>runqemu-extract-sdk</filename> script,
                    which is located in the <filename>scripts</filename>
                    directory along with the <filename>runqemu</filename>
                    script.</para>

                    <para>The <filename>runqemu-extract-sdk</filename> takes a
                    root filesystem tarball and extracts it into a location
                    that you specify.
                    Here is an example that takes a file system and
                    extracts it to a directory named
                    <filename>test-nfs</filename>:
                    <literallayout class='monospaced'>
     runqemu-extract-sdk ./tmp/deploy/images/qemux86/core-image-sato-qemux86.tar.bz2 test-nfs
                    </literallayout>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Start QEMU:</emphasis>
                    Once you have extracted the file system, you can run
                    <filename>runqemu</filename> normally with the additional
                    location of the file system.
                    You can then also make changes to the files within
                    <filename>./test-nfs</filename> and see those changes
                    appear in the image in real time.
                    Here is an example using the <filename>qemux86</filename>
                    image:
                    <literallayout class='monospaced'>
     runqemu qemux86 ./test-nfs
                    </literallayout>
                    </para></listitem>
            </orderedlist>
            <note>
                <para>
                    Should you need to start, stop, or restart the NFS share,
                    you can use the following commands:
                    <itemizedlist>
                        <listitem><para>
                            The following command starts the NFS share:
                            <literallayout class='monospaced'>
     runqemu-export-rootfs start <replaceable>file-system-location</replaceable>
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            The following command stops the NFS share:
                            <literallayout class='monospaced'>
         runqemu-export-rootfs stop <replaceable>file-system-location</replaceable>
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            The following command restarts the NFS share:
                            <literallayout class='monospaced'>
     runqemu-export-rootfs restart <replaceable>file-system-location</replaceable>
                            </literallayout>
                            </para></listitem>
                    </itemizedlist>
                </para>
            </note>
        </para>
    </section>
</chapter>
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