434 lines
21 KiB
XML
434 lines
21 KiB
XML
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
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[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
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<chapter id='dev-manual-qemu'>
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<title>Using the Quick EMUlator (QEMU)</title>
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<para>
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Quick EMUlator (QEMU) is an Open Source project the Yocto Project uses
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as part of its development "tool set".
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As such, the information in this chapter is limited to the
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Yocto Project integration of QEMU and not QEMU in general.
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For official information and documentation on QEMU, see the
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following references:
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<itemizedlist>
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<listitem><para><emphasis><ulink url='http://wiki.qemu.org/Main_Page'>QEMU Website</ulink>:</emphasis>
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The official website for the QEMU Open Source project.
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</para></listitem>
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<listitem><para><emphasis><ulink url='http://wiki.qemu.org/Manual'>Documentation</ulink>:</emphasis>
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The QEMU user manual.
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</para></listitem>
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</itemizedlist>
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</para>
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<para>
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This chapter provides an overview of the Yocto Project's integration of
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QEMU, a description of how you use QEMU and its various options, running
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under a Network File System (NFS) server, and a few tips and tricks you
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might find helpful when using QEMU.
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</para>
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<section id='qemu-overview'>
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<title>Overview</title>
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<para>
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Within the context of the Yocto Project, QEMU is an
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emulator and virtualization machine that allows you to run a complete
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image you have built using the Yocto Project as just another task
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on your build system.
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QEMU is useful for running and testing images and applications on
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supported Yocto Project architectures without having actual hardware.
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Among other things, the Yocto Project uses QEMU to run automated
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Quality Assurance (QA) tests on final images shipped with each
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release.
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</para>
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<para>
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QEMU is made available with the Yocto Project a number of ways.
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One method is to install a Software Development Kit (SDK).
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For more information on how to make sure you have
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QEMU available, see the
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<ulink url='&YOCTO_DOCS_SDK_URL;#sdk-intro'>Yocto Project Software Development Kit (SDK) Developer's Guide</ulink>.
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</para>
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</section>
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<section id='qemu-running-qemu'>
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<title>Running QEMU</title>
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<para>
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Running QEMU involves having your build environment set up, having the
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right artifacts available, and understanding how to use the many
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options that are available to you when you start QEMU using the
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<filename>runqemu</filename> command.
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</para>
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<section id='qemu-setting-up-the-environment'>
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<title>Setting Up the Environment</title>
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<para>
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You run QEMU in the same environment from which you run BitBake.
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This means you need to source a build environment script (i.e.
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<ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink>
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or
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<ulink url='&YOCTO_DOCS_REF_URL;#structure-memres-core-script'><filename>oe-init-build-env-memres</filename></ulink>).
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</para>
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</section>
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<section id='qemu-using-the-runqemu-command'>
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<title>Using the <filename>runqemu</filename> Command</title>
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<para>
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The basic <filename>runqemu</filename> command syntax is as
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follows:
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<literallayout class='monospaced'>
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$ runqemu [<replaceable>option</replaceable> ] [...]
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</literallayout>
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Based on what you provide on the command line,
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<filename>runqemu</filename> does a good job of figuring out what
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you are trying to do.
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For example, by default, QEMU looks for the most recently built
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image according to the timestamp when it needs to look for an
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image.
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Minimally, through the use of options, you must provide either
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a machine name, a virtual machine image
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(<filename>*.vmdk</filename>), or a kernel image
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(<filename>*.bin</filename>).
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</para>
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<para>
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Following is a description of <filename>runqemu</filename>
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options you can provide on the command line:
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<note><title>Tip</title>
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If you do provide some "illegal" option combination or perhaps
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you do not provide enough in the way of options,
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<filename>runqemu</filename> provides appropriate error
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messaging to help you correct the problem.
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</note>
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<itemizedlist>
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<listitem><para><replaceable>QEMUARCH</replaceable>:
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The QEMU machine architecture, which must be "qemux86",
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"qemux86_64", "qemuarm", "qemumips", "qemumipsel",
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“qemumips64", "qemush4", "qemuppc", "qemumicroblaze",
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or "qemuzynq".
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</para></listitem>
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<listitem><para><filename><replaceable>VM</replaceable></filename>:
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The virtual machine image, which must be a
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<filename>.vmdk</filename> file.
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Use this option when you want to boot a
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<filename>.vmdk</filename> image.
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The image filename you provide must contain one of the
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following strings: "qemux86-64", "qemux86", "qemuarm",
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"qemumips64", "qemumips", "qemuppc", or "qemush4".
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</para></listitem>
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<listitem><para><replaceable>ROOTFS</replaceable>:
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A root filesystem that has one of the following
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filetype extensions: "ext2", "ext3", "ext4", "jffs2",
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"nfs", or "btrfs".
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If the filename you provide for this option uses “nfs”, it
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must provide an explicit root filesystem path.
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</para></listitem>
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<listitem><para><replaceable>KERNEL</replaceable>:
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A kernel image, which is a <filename>.bin</filename> file.
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When you provide a <filename>.bin</filename> file,
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<filename>runqemu</filename> detects it and assumes the
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file is a kernel image.
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</para></listitem>
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<listitem><para><replaceable>MACHINE</replaceable>:
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The architecture of the QEMU machine, which must be one
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of the following: "qemux86",
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"qemux86-64", "qemuarm", "qemumips", "qemumipsel",
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“qemumips64", "qemush4", "qemuppc", "qemumicroblaze",
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or "qemuzynq".
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The <replaceable>MACHINE</replaceable> and
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<replaceable>QEMUARCH</replaceable> options are basically
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identical.
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If you do not provide a <replaceable>MACHINE</replaceable>
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option, <filename>runqemu</filename> tries to determine
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it based on other options.
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</para></listitem>
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<listitem><para><filename>ramfs</filename>:
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Indicates you are booting an initial RAM disk (initramfs)
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image, which means the <filename>FSTYPE</filename> is
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<filename>cpio.gz</filename>.
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</para></listitem>
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<listitem><para><filename>iso</filename>:
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Indicates you are booting an ISO image, which means the
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<filename>FSTYPE</filename> is
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<filename>.iso</filename>.
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</para></listitem>
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<listitem><para><filename>nographic</filename>:
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Disables the video console, which sets the console to
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"ttys0".
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</para></listitem>
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<listitem><para><filename>serial</filename>:
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Enables a serial console on
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<filename>/dev/ttyS0</filename>.
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</para></listitem>
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<listitem><para><filename>biosdir</filename>:
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Establishes a custom directory for BIOS, VGA BIOS and
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keymaps.
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</para></listitem>
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<listitem><para><filename>biosfilename</filename>:
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Establishes a custom BIOS name.
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</para></listitem>
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<listitem><para><filename>qemuparams=\"<replaceable>xyz</replaceable>\"</filename>:
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Specifies custom QEMU parameters.
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Use this option to pass options other than the simple
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"kvm" and "serial" options.
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</para></listitem>
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<listitem><para><filename>bootparams=\"<replaceable>xyz</replaceable>\"</filename>:
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Specifies custom boot parameters for the kernel.
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</para></listitem>
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<listitem><para><filename>audio</filename>:
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Enables audio in QEMU.
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The <replaceable>MACHINE</replaceable> option must be
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either "qemux86" or "qemux86-64" in order for audio to be
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enabled.
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Additionally, the <filename>snd_intel8x0</filename>
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or <filename>snd_ens1370</filename> driver must be
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installed in linux guest.
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</para></listitem>
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<listitem><para><filename>slirp</filename>:
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Enables "slirp" networking, which is a different way
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of networking that does not need root access
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but also is not as easy to use or comprehensive
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as the default.
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</para></listitem>
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<listitem><para id='kvm-cond'><filename>kvm</filename>:
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Enables KVM when running "qemux86" or "qemux86-64"
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QEMU architectures.
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For KVM to work, all the following conditions must be met:
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<itemizedlist>
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<listitem><para>
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Your <replaceable>MACHINE</replaceable> must be either
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qemux86" or "qemux86-64".
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</para></listitem>
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<listitem><para>
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Your build host has to have the KVM modules
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installed, which are
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<filename>/dev/kvm</filename>.
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</para></listitem>
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<listitem><para>
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The build host <filename>/dev/kvm</filename>
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directory has to be both writable and readable.
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</para></listitem>
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</itemizedlist>
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</para></listitem>
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<listitem><para><filename>kvm-vhost</filename>:
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Enables KVM with VHOST support when running "qemux86" or "qemux86-64"
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QEMU architectures.
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For KVM with VHOST to work, the following conditions must
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be met:
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<itemizedlist>
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<listitem><para>
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<link linkend='kvm-cond'>kvm</link> option
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conditions must be met.
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</para></listitem>
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<listitem><para>
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Your build host has to have virtio net device, which
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are <filename>/dev/vhost-net</filename>.
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</para></listitem>
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<listitem><para>
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The build host <filename>/dev/vhost-net</filename>
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directory has to be either readable or writable
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and “slirp-enabled”.
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</para></listitem>
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</itemizedlist>
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</para></listitem>
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<listitem><para><filename>publicvnc</filename>:
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Enables a VNC server open to all hosts.
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</para></listitem>
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</itemizedlist>
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</para>
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<para>
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For further understanding regarding option use with
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<filename>runqemu</filename>, consider some examples.
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</para>
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<para>
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This example starts QEMU with
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<replaceable>MACHINE</replaceable> set to "qemux86".
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Assuming a standard
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<link linkend='build-directory'>Build Directory</link>,
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<filename>runqemu</filename> automatically finds the
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<filename>bzImage-qemux86.bin</filename> image file and
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the
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<filename>core-image-minimal-qemux86-20140707074611.rootfs.ext3</filename>
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(assuming the current build created a
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<filename>core-image-minimal</filename> image).
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<note>
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When more than one image with the same name exists, QEMU finds
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and uses the most recently built image according to the
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timestamp.
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</note>
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<literallayout class='monospaced'>
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$ runqemu qemux86
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</literallayout>
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This example produces the exact same results as the
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previous example.
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This command, however, specifically provides the image
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and root filesystem type.
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<literallayout class='monospaced'>
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$ runqemu qemux86 core-image-minimal ext3
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</literallayout>
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This example specifies to boot an initial RAM disk image
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and to enable audio in QEMU.
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For this case, <filename>runqemu</filename> set the
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internal variable <filename>FSTYPE</filename> to
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"cpio.gz".
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Also, for audio to be enabled, an appropriate driver must
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be installed (see the previous description for the
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<filename>audio</filename> option for more information).
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<literallayout class='monospaced'>
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$ runqemu qemux86 ramfs audio
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</literallayout>
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This example does not provide enough information for
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QEMU to launch.
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While the command does provide a root filesystem type, it
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must also minimally provide a
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<replaceable>MACHINE</replaceable>,
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<replaceable>KERNEL</replaceable>, or
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<replaceable>VM</replaceable> option.
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<literallayout class='monospaced'>
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$ runqemu ext3
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</literallayout>
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This example specifies to boot a virtual machine image
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(<filename>.vmdk</filename> file).
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From the <filename>.vmdk</filename>,
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<filename>runqemu</filename> determines the QEMU
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architecture (<replaceable>MACHINE</replaceable>) to be
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"qemux86" and the root filesystem type to be "vmdk".
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<literallayout class='monospaced'>
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$ runqemu /home/scott-lenovo/vm/core-image-minimal-qemux86.vmdk
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</literallayout>
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</para>
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</section>
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</section>
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<section id='qemu-running-under-a-network-file-system-nfs-server'>
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<title>Running Under a Network File System (NFS) Server</title>
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<para>
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One method for running QEMU is to run it on an NFS server.
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This is useful when you need to access the same file system from both
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the build and the emulated system at the same time.
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It is also worth noting that the system does not need root privileges
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to run.
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It uses a user space NFS server to avoid that.
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This section describes how to set up for running QEMU using an NFS
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server and then how you can start and stop the server.
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</para>
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<section id='qemu-setting-up-to-use-nfs'>
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<title>Setting Up to Use NFS</title>
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<para>
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Once you are able to run QEMU in your environment, you can use the
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<filename>runqemu-extract-sdk</filename> script, which is located
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in the <filename>scripts</filename> directory along with
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<filename>runqemu</filename> script.
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The <filename>runqemu-extract-sdk</filename> takes a root
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file system tarball and extracts it into a location that you
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specify.
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Then, when you run <filename>runqemu</filename>, you can specify
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the location that has the file system to pass it to QEMU.
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Here is an example that takes a file system and extracts it to
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a directory named <filename>test-nfs</filename>:
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<literallayout class='monospaced'>
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runqemu-extract-sdk ./tmp/deploy/images/qemux86/core-image-sato-qemux86.tar.bz2 test-nfs
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</literallayout>
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Once you have extracted the file system, you can run
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<filename>runqemu</filename> normally with the additional
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location of the file system.
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You can then also make changes to the files within
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<filename>./test-nfs</filename> and see those changes appear in the
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image in real time.
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Here is an example using the <filename>qemux86</filename> image:
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<literallayout class='monospaced'>
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runqemu qemux86 ./test-nfs
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</literallayout>
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</para>
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</section>
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<section id='qemu-starting-and-stopping-nfs'>
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<title>Starting and Stopping NFS</title>
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<para>
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You can manually start and stop the NFS share using these
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commands:
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<itemizedlist>
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<listitem><para><emphasis><filename>start</filename>:</emphasis>
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Starts the NFS share:
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<literallayout class='monospaced'>
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runqemu-export-rootfs start <replaceable>file-system-location</replaceable>
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</literallayout>
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</para></listitem>
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<listitem><para><emphasis><filename>stop</filename>:</emphasis>
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Stops the NFS share:
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<literallayout class='monospaced'>
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runqemu-export-rootfs stop <replaceable>file-system-location</replaceable>
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</literallayout>
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</para></listitem>
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<listitem><para><emphasis><filename>restart</filename>:</emphasis>
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Restarts the NFS share:
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<literallayout class='monospaced'>
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runqemu-export-rootfs restart <replaceable>file-system-location</replaceable>
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</literallayout>
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</para></listitem>
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</itemizedlist>
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</para>
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</section>
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</section>
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<section id='qemu-tips-and-tricks'>
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<title>Tips and Tricks</title>
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<para>
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The following list describes things you can do to make running QEMU
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in the context of the Yocto Project a better experience:
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<itemizedlist>
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<listitem><para><emphasis>Switching Between Consoles:</emphasis>
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When booting or running QEMU, you can switch between
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supported consoles by using
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Ctrl+Alt+<replaceable>number</replaceable>.
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For example, Ctrl+Alt+3 switches you to the serial console as
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long as that console is enabled.
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Being able to switch consoles is helpful, for example, if the
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main QEMU console breaks for some reason.
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<note>
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Usually, "2" gets you to the main console and "3" gets you
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to the serial console.
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</note>
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</para></listitem>
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<listitem><para><emphasis>Removing the Splash Screen:</emphasis>
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You can remove the splash screen when QEMU is booting by
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using Alt+left.
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Removing the splash screen allows you to see what is happening
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in the background.
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</para></listitem>
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<listitem><para><emphasis>Disabling the Cursor Grab:</emphasis>
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The default QEMU integration captures the cursor within the
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main window.
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It does this since standard mouse devices only provide relative
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input and not absolute coordinates.
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You then have to break out of the grab using the "Ctrl+Alt" key
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combination.
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However, the Yocto Project's integration of QEMU enables the
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wacom USB touch pad driver by default to allow input of absolute
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coordinates.
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This default means that the mouse can enter and leave the
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main window without the grab taking effect leading to a better
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user experience.
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</para></listitem>
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</itemizedlist>
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</para>
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</section>
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</chapter>
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<!--
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vim: expandtab tw=80 ts=4
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-->
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