user_Troubleshooting.xml revision ac153c99053f1edf42b00bf3a13475923bc4fcf1
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6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>This chapter provides answers to commonly asked questions. In order to
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync improve your user experience with VirtualBox, it is recommended to read this
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync section to learn more about common pitfalls and get recommendations on how
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync to use the product.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>More often than not, a virtualized guest behaves like a physical
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync system. Any problems that a physical machine would encounter, a virtual
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync machine will encounter as well. If, for example, Internet connectivity
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync is lost due to external issues, virtual machines will be affected just
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync as much as physical ones.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>If a true VirtualBox problem is encountered, it helps to
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync categorize and isolate the problem first. Here are some of the questions
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync that should be answered before reporting a problem:<orderedlist>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Is the problem specific to a certain guest OS? Specific
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync release of a guest OS? Especially with Linux guest related
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync problems, the issue may be specific to a certain distribution and
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync version of Linux.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Is the problem specific to a certain host OS? Problems are
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync usually not host OS specific (because most of the VirtualBox code
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync base is shared across all supported platforms), but especially in
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the areas of networking and USB support, there are significant
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync differences between host platforms. Some GUI related issues are
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync also host specific.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Is the problem specific to certain host hardware? This
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync category of issues is typically related to the host CPU. Because
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync of significant differences between VT-x and AMD-V, problems may be
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync specific to one or the other technology. The exact CPU model may
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync also make a difference (even for software virtualization) because
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync different CPUs support different features, which may affect
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync certain aspects of guest CPU operation.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Is the problem specific to a certain virtualization mode?
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync Some problems may only occur in software virtualization mode,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync others may be specific to hardware virtualization.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Is the problem specific to guest SMP? That is, is it related
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync to the number of virtual CPUs (VCPUs) in the guest? Using more
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync than one CPU usually significantly affects the internal operation
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync of a guest OS.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Is the problem specific to the Guest Additions? In some
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync cases, this is a given (e.g., a shared folders problem), in other
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync cases it may be less obvious (for example, display problems). And
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync if the problem is Guest Additions specific, is it also specific to
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync a certain version of the Additions?</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Is the problem specific to a certain environment? Some
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync problems are related to a particular environment external to the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync VM; this usually involves network setup. Certain configurations of
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync external servers such as DHCP or PXE may expose problems which do
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync not occur with other, similar servers.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Is the problem a regression? Knowing that an issue is a
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync regression usually makes it significantly easier to find the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync solution. In this case, it is crucial to know which version is
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync affected and which is not.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>For problem determination, it is often important to collect
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync debugging information which can be analyzed by VirtualBox support. This
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync section contains information about what kind of information can be
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync obtained.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Every time VirtualBox starts up a VM, a so-called <emphasis
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync role="bold">"release log file"</emphasis> is created containing lots of
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync information about the VM configuration and runtime events. The log file
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync is called <computeroutput><literal>VBox.log</literal></computeroutput>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync and resides in the VM log file folder. Typically this will be a
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync directory like this:<screen>$HOME/VirtualBox VMs/{machinename}/Logs</screen></para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>When starting a VM, the configuration file of the last run will be
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync renamed to <computeroutput>.1</computeroutput>, up to
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>.3</computeroutput>. Sometimes when there is a problem,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync it is useful to have a look at the logs. Also when requesting support
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync for VirtualBox, supplying the corresponding log file is
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync mandatory.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>For convenience, for each virtual machine, the VirtualBox main
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync window can show these logs in a window. To access it, select a virtual
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync machine from the list on the left and select "Show logs..." from the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync "Machine" window.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The release log file (VBox.log) contains a wealth of diagnostic
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync information, such as Host OS type and version, VirtualBox version and
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync build (32-bit or 64-bit), a complete dump of the guest's configuration
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync (CFGM), detailed information about the host CPU type and supported
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync features, whether hardware virtualization is enabled, information about
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync VT-x/AMD-V setup, state transitions (creating, running, paused,
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync stopping, etc.), guest BIOS messages, Guest Additions messages,
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync device-specific log entries and, at the end of execution, final guest
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync state and condensed statistics.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>In case of crashes, it is very important to collect <emphasis
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync role="bold">crash dumps</emphasis>. This is true for both host and guest
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync crashes. For information about enabling core dumps on Linux, Solaris,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync and OS X systems, refer to the core dump article on the VirtualBox
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync website.<footnote>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync url="http://www.virtualbox.org/wiki/Core_dump">http://www.virtualbox.org/wiki/Core_dump</ulink>.</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync debugvm</computeroutput> to create a dump of a complete virtual machine;
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>For network related problems, it is often helpful to capture a
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync trace of network traffic. If the traffic is routed through an adapter on
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the host, it is possible to use Wireshark or a similar tool to capture
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the traffic there. However, this often also includes a lot of traffic
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync unrelated to the VM.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>VirtualBox provides an ability to capture network traffic only on
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync a specific VM's network adapter. Refer to the network tracing article on
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the VirtualBox website<footnote>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync url="http://www.virtualbox.org/wiki/Network_tips">http://www.virtualbox.org/wiki/Network_tips</ulink>.</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync </footnote> for information on enabling this capture. The trace files
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync created by VirtualBox are in <computeroutput>.pcap</computeroutput>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync format and can be easily analyzed with Wireshark.</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <title id="debugger">The built-in VM debugger</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>VirtualBox includes a built-in VM debugger, which advanced users
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync may find useful. This debugger allows for examining and, to some extent,
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync controlling the VM state.<warning>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Use the VM debugger at your own risk. There is no support for
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync it, and the following documentation is only made available for
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync advanced users with a very high level of familiarity with the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync x86/AMD64 machine instruction set, as well as detailed knowledge of
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the PC architecture. A degree of familiarity with the internals of
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync the guest OS in question may also be very helpful.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The VM debugger is available in all regular production versions of
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync VirtualBox, but it is disabled by default because the average user will
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync have little use for it. There are two ways to access the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync debugger:<itemizedlist>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>A debugger console window displayed alongside the VM</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Via the <computeroutput>telnet</computeroutput> protocol at
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync port 5000</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The debugger can be enabled in three ways:<itemizedlist>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>Start the VM directly using <computeroutput>VirtualBox
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync --startvm</computeroutput>, with an additional
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>--debug-command-line</computeroutput> argument.
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync See the VirtualBox usage help for details.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Set the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>VBOX_GUI_DBG_ENABLED</computeroutput> or
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>VBOX_GUI_DBG_AUTO_SHOW</computeroutput>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync environment variable to <computeroutput>true</computeroutput>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync before launching the VirtualBox process. Setting these variables
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync (only their presence is checked) is effective even when the first
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync VirtualBox process is the VM selector window. VMs subsequently
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync launched from the selector will have the debugger enabled.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Set the <computeroutput>GUI/Dbg/Enabled</computeroutput>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync extra data item to <computeroutput>true</computeroutput> before
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync launching the VM. This can be set globally or on a per VM
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync basis.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>A new 'Debug' menu entry will be added to the VirtualBox
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync application. This menu allows the user to open the debugger
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync console.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The VM debugger command syntax is loosely modeled on Microsoft and
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync IBM debuggers used on DOS, OS/2 and Windows. Users familiar with symdeb,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync CodeView, or the OS/2 kernel debugger will find the VirtualBox VM
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync debugger familiar.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The most important command is
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>help</computeroutput>. This will print brief usage help
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync for all debugger commands. The set of commands supported by the VM
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync debugger changes frequently and the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>help</computeroutput> command is always
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync up-to-date.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>A brief summary of frequently used commands follows:<itemizedlist>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>stop</computeroutput> -- stops the VM
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync execution and enables single stepping</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>g</computeroutput> -- continue VM
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync execution</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>t</computeroutput> -- single step an
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync instruction</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>rg/rh/r</computeroutput> -- print the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>kg/kh/k</computeroutput> -- print the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>da/db/dw/dd/dq</computeroutput> -- print
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync memory contents as ASCII/bytes/words/dwords/qwords</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>u</computeroutput> -- unassemble
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync memory</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>dg</computeroutput> -- print the guest's
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>di</computeroutput> -- print the guest's
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>dl</computeroutput> -- print the guest's
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>dt</computeroutput> -- print the guest's
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>dp*</computeroutput> -- print the guest's
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync page table structures</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>bp/br</computeroutput> -- set a
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync breakpoints</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>bc</computeroutput> -- clear a
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync breakpoint</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>writecore</computeroutput> -- writes a VM
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync core file to disk, refer <xref linkend="guestcoreformat" /></para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>See the built-in <computeroutput>help</computeroutput> for other
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync available commands.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The VM debugger supports symbolic debugging, although symbols for
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync guest code are often not available. For Solaris guests, the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>detect</computeroutput> command automatically determines
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the guest OS version and locates kernel symbols in guest's memory.
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync Symbolic debugging is then available. For Linux guests, the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>detect</computeroutput> commands also determines the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync guest OS version, but there are no symbols in the guest's memory. Kernel
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync symbols are available in the file
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>/proc/kallsyms</computeroutput> on Linux guests. This
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync file must be copied to the host, for example using
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>loadmap</computeroutput> debugger command can be used to
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync make the symbol information available to the VM debugger. Note that the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>kallsyms</computeroutput> file contains the symbols for
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the currently loaded modules; if the guest's configuration changes, the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync symbols will change as well and must be updated.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>For all guests, a simple way to verify that the correct symbols
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync are loaded is the <computeroutput>k</computeroutput> command. The guest
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync is normally idling and it should be clear from the symbolic information
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync that the guest operating system's idle loop is being executed.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Another group of debugger commands is the set of
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>info</computeroutput> commands. Running
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>info help</computeroutput> provides complete usage
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync information. The information commands provide ad-hoc data pertinent to
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync various emulated devices and aspects of the VMM. There is no general
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync guideline for using the <computeroutput>info</computeroutput> commands,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the right command to use depends entirely on the problem being
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync investigated. Some of the info commands are:<itemizedlist>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>cfgm</computeroutput> -- print a branch of
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the configuration tree</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>cpuid</computeroutput> -- display the guest
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync CPUID leaves</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>ioport</computeroutput> -- print registered
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync I/O port ranges</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>mmio</computeroutput> -- print registered
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync MMIO ranges</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>mode</computeroutput> -- print the current
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync paging mode</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>pit</computeroutput> -- print the i8254 PIT
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync state</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>pic</computeroutput> -- print the i8259A PIC
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync state</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>ohci/ehci</computeroutput> -- print a subset
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>pcnet0</computeroutput> -- print the PCnet
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync state</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>vgatext</computeroutput> -- print the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync contents of the VGA framebuffer formatted as standard text
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync mode</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><computeroutput>timers</computeroutput> -- print all VM
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync timers</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The output of the <computeroutput>info</computeroutput> commands
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync generally requires in-depth knowledge of the emulated device and/or
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync VirtualBox VMM internals. However, when used properly, the information
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync provided can be invaluable.</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>VirtualBox uses the 64-bit ELF format for its VM core files
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync created by <computeroutput>VBoxManage debugvm</computeroutput>; see
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <xref linkend="vboxmanage-debugvm" />. The VM core file contain the
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync memory and CPU dumps of the VM and can be useful for debugging your
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync guest OS. The 64-bit ELF object format specficiation can be obtained
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync url="http://downloads.openwatcom.org/ftp/devel/docs/elf-64-gen.pdf">http://downloads.openwatcom.org/ftp/devel/docs/elf-64-gen.pdf</ulink></literal>.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The overall layout of the VM core format is as follows:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync[ Program Header, type PT_NOTE ]
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync -> offset to COREDESCRIPTOR
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync[ Program Header, type PT_LOAD ] - one for each contiguous physical memory range
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync -> Memory offset of range
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync -> File offset
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync[ Note Header, type NT_VBOXCORE ]
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync[ COREDESCRIPTOR ]
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync -> Magic
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync -> VM core file version
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync -> VBox version
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync -> Number of vCPUs etc.
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync[ Note Header, type NT_VBOXCPU ] - one for each vCPU
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync[ vCPU 1 Note Header ]
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync [ CPUMCTX - vCPU 1 dump ]
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync[ Additional Notes + Data ] - currently unused
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The memory descriptors contain physical addresses relative to the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync guest and not virtual addresses. Regions of memory such as MMIO regions
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync are not included in the core file.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The relevant data structures and definitions can be found in the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync VirtualBox sources under the following header files:
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>include/VBox/dbgfcorefmt.h</computeroutput>,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>include/VBox/cpumctx.h</computeroutput> and
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>src/VBox/Runtime/include/internal/ldrELFCommon.h</computeroutput>.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The VM core file can be inspected using
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>readelf</computeroutput> or other similar
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync utilities.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>Guest shows IDE/SATA errors for file-based images on slow host
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync file system</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Occasionally, some host file systems provide very poor writing
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync performance and as a consequence cause the guest to time out IDE/SATA
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync commands. This is normal behavior and should normally cause no real
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync problems, as the guest should repeat commands that have timed out.
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync However some guests (e.g. some Linux versions) have severe problems if a
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync write to an image file takes longer than about 15 seconds. Some file
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync systems however require more than a minute to complete a single write,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync if the host cache contains a large amount of data that needs to be
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync written.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The symptom for this problem is that the guest can no longer
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync access its files during large write or copying operations, usually
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync leading to an immediate hang of the guest.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>In order to work around this problem (the true fix is to use a
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync faster file system that doesn't exhibit such unacceptable write
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync performance), it is possible to flush the image file after a certain
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync amount of data has been written. This interval is normally infinite, but
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync can be configured individually for each disk of a VM.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>For IDE disks use the following command:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <screen>VBoxManage setextradata "VM name"
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync "VBoxInternal/Devices/piix3ide/0/LUN#[x]/Config/FlushInterval" [b]</screen>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>For SATA disks use the following command:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <screen>VBoxManage setextradata "VM name"
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync "VBoxInternal/Devices/ahci/0/LUN#[x]/Config/FlushInterval" [b]</screen>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The value [x] that selects the disk for IDE is 0 for the master
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync device on the first channel, 1 for the slave device on the first
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync channel, 2 for the master device on the second channel or 3 for the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync master device on the second channel. For SATA use values between 0 and
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync 29. Only disks support this configuration option; it must not be set for
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The unit of the interval [b] is the number of bytes written since
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the last flush. The value for it must be selected so that the occasional
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync long write delays do not occur. Since the proper flush interval depends
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync on the performance of the host and the host filesystem, finding the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync optimal value that makes the problem disappear requires some
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync experimentation. Values between 1000000 and 10000000 (1 to 10 megabytes)
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync are a good starting point. Decreasing the interval both decreases the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync probability of the problem and the write performance of the guest.
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync Setting the value unnecessarily low will cost performance without
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync providing any benefits. An interval of 1 will cause a flush for each
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync write operation and should solve the problem in any case, but has a
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync severe write performance penalty.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Providing a value of 0 for [b] is treated as an infinite flush
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync interval, effectively disabling this workaround. Removing the extra data
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync key by specifying no value for [b] has the same effect.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>Responding to guest IDE/SATA flush requests</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>If desired, the virtual disk images can be flushed when the guest
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync issues the IDE FLUSH CACHE command. Normally these requests are ignored
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync for improved performance. The parameters below are only accepted for
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync disk drives. They must not be set for DVD drives.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>To enable flushing for IDE disks, issue the following
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync command:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <screen>VBoxManage setextradata "VM name" "VBoxInternal/Devices/piix3ide/0/LUN#[x]/Config/IgnoreFlush" 0</screen>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The value [x] that selects the disk is 0 for the master device on
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the first channel, 1 for the slave device on the first channel, 2 for
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the master device on the second channel or 3 for the master device on
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the second channel.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>To enable flushing for SATA disks, issue the following
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync command:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <screen>VBoxManage setextradata "VM name" "VBoxInternal/Devices/ahci/0/LUN#[x]/Config/IgnoreFlush" 0</screen>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The value [x] that selects the disk can be a value between 0 and
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Note that this doesn't affect the flushes performed according to
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the configuration described in <xref linkend="configPeriodicFlush"
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync xrefstyle="template: %n" />. Restoring the default of ignoring flush
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync commands is possible by setting the value to 1 or by removing the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync key.</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <title>Poor performance caused by host power management</title>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>On some hardware platforms and operating systems, virtualization
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync performance is negatively affected by host CPU power management. The
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync symptoms may be choppy audio in the guest or erratic guest clock
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync behavior.</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>Some of the problems may be caused by firmware and/or host
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync operating system bugs. Therefore, updating the firmware and applying
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync operating systems fixes is recommended.</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>For optimal virtualization performance, the C1E power state
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync support in the system's BIOS should be disabled, if such a setting is
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync available (not all systems support the C1E power state). Disabling other
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync power management settings may also improve performance. However, a
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync balance between performance and power consumption must always be
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync considered.</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <title>GUI: 2D Video Acceleration option is grayed out</title>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>To use 2D Video Acceleration within VirtualBox, your host's video
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync card should support certain OpenGL extensions. On startup, VirtualBox
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync checks for those extensions, and, if the test fails, this option is
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync silently grayed out.</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>To find out why it has failed, you can manually execute the
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync following command:</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <screen>VBoxTestOGL --log "log_file_name" --test 2D</screen>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>It will list the required OpenGL extensions one by one and will
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync show you which one failed the test. This usually means that you are
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync running an outdated or misconfigured OpenGL driver on your host. It can
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync also mean that your video chip is lacking required functionality.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>Windows bluescreens after changing VM configuration</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Changing certain virtual machine settings can cause Windows guests
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync to fail during start up with a bluescreen. This may happen if you change
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync VM settings after installing Windows, or if you copy a disk image with
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync an already installed Windows to a newly created VM which has settings
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync that differ from the original machine.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>This applies in particular to the following settings:<itemizedlist>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The ACPI and I/O APIC settings should never be changed after
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync installing Windows. Depending on the presence of these hardware
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync features, the Windows installation program chooses special kernel
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync and device driver versions and will fail to startup should these
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync hardware features be removed. (Enabling them for a Windows VM
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync which was installed without them does not cause any harm. However,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync Windows will not use these features in this case.)</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Changing the storage controller hardware will cause bootup
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync failures as well. This might also apply to you if you copy a disk
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync image from an older version of VirtualBox to a virtual machine
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync created with a newer VirtualBox version; the default subtype of
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync IDE controller hardware was changed from PIIX3 to PIIX4 with
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync VirtualBox 2.2. Make sure these settings are identical.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>Windows 0x101 bluescreens with SMP enabled (IPI timeout)</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>If a VM is configured to have more than one processor (symmetrical
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync multiprocessing, SMP), some configurations of Windows guests crash with
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync an 0x101 error message, indicating a timeout for inter-processor
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync interrupts (IPIs). These interrupts synchronize memory management
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync between processors.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>According to Microsoft, this is due to a race condition in
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync Windows. A hotfix is available.<footnote>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync url="http://support.microsoft.com/kb/955076">http://support.microsoft.com/kb/955076</ulink>.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </footnote> If this does not help, please reduce the number of virtual
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync processors to 1.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>When installing Windows 2000 guests, you might run into one of the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync following issues:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <itemizedlist>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Installation reboots, usually during component
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync registration.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Installation fills the whole hard disk with empty log
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync files.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Installation complains about a failure installing
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </itemizedlist>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>These problems are all caused by a bug in the hard disk driver of
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync Windows 2000. After issuing a hard disk request, there is a race
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync condition in the Windows driver code which leads to corruption if the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync operation completes too fast, i.e. the hardware interrupt from the IDE
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync controller arrives too soon. With physical hardware, there is a
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync guaranteed delay in most systems so the problem is usually hidden there
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync (however it should be possible to reproduce it on physical hardware as
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync well). In a virtual environment, it is possible for the operation to be
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync done immediately (especially on very fast systems with multiple CPUs)
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync and the interrupt is signaled sooner than on a physical system. The
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync solution is to introduce an artificial delay before delivering such
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync interrupts. This delay can be configured for a VM using the following
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync command:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <screen>VBoxManage setextradata "VM name" "VBoxInternal/Devices/piix3ide/0/Config/IRQDelay" 1</screen>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>This sets the delay to one millisecond. In case this doesn't help,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync increase it to a value between 1 and 5 milliseconds. Please note that
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync this slows down disk performance. After installation, you should be able
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync to remove the key (or set it to 0).</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>How to record bluescreen information from Windows guests</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>When Windows guests run into a kernel crash, they display the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync infamous bluescreen. Depending on how Windows is configured, the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync information will remain on the screen until the machine is restarted or
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync it will reboot automatically. During installation, Windows is usually
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync configured to reboot automatically. With automatic reboots, there is no
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync chance to record the bluescreen information which might be important for
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync problem determination.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>VirtualBox provides a method of halting a guest when it wants to
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync perform a reset. In order to enable this feature, issue the following
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync command:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><screen>VBoxManage setextradata "VM name" "VBoxInternal/PDM/HaltOnReset" 1</screen></para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>No networking in Windows Vista guests</title>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>With Windows Vista, Microsoft dropped support for the AMD PCNet
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync card that VirtualBox used to provide as the default virtual network card
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync before version 1.6.0. For Windows Vista guests, VirtualBox now uses an
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync Intel E1000 card by default.</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>If, for some reason, you still want to use the AMD card, you need
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync to download the PCNet driver from the AMD website (available for 32-bit
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync Windows only). You can transfer it into the virtual machine using a
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync shared folder, see (see <xref linkend="sharedfolders" />).</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>Windows guests may cause a high CPU load</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Several background applications of Windows guests, especially
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync virus scanners, are known to increases the CPU load notably even if the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync guest appears to be idle. We recommend to deactivate virus scanners
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync within virtualized guests if possible.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>Long delays when accessing shared folders</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The performance for accesses to shared folders from a Windows
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync guest might be decreased due to delays during the resolution of the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync VirtualBox shared folders name service. To fix these delays, add the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync following entries to the file
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>\windows\system32\drivers\etc\lmhosts</computeroutput>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync of the Windows guest:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <screen>255.255.255.255 VBOXSVR #PRE
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync255.255.255.255 VBOXSRV #PRE</screen>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>After doing this change, a reboot of the guest is required.</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <title>USB tablet coordinates wrong in Windows 98 guests</title>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>If a Windows 98 VM is configured to use the emulated USB tablet
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync (absolute pointing device), the coordinate translation may be incorrect
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync and the pointer is restricted to the upper left quarter of the guest's
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>The USB HID (Human Interface Device) drivers in Windows 98 are very
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync old and do not handle tablets the same way all more recent operating
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync systems do (Windows 2000 and later, Mac OS X, Solaris). To
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync work around the problem, issue the following command:
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para><screen>VBoxManage setextradata "VM name" "VBoxInternal/USB/HidMouse/0/Config/CoordShift" 0</screen></para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>To restore the default behavior, remove the key or set its value
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <title>Windows guests are removed from an Active Directory domain after
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync restoring a snapshot</title>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>If a Windows guest is a member of an Active Directory domain and
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync the snapshot feature of VirtualBox is used, it could happen it loses
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync this status after you restore an older snapshot.
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>The reason is the automatic machine password changing performed by
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync Windows in regular intervals for security purposes. You can disable
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync this feature by following the instruction of this <ulink
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync url="http://support.microsoft.com/kb/154501">http://support.microsoft.com/kb/154501</ulink>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync article from Microsoft.
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>Linux guests may cause a high CPU load</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Some Linux guests may cause a high CPU load even if the guest
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync system appears to be idle. This can be caused by a high timer frequency
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync of the guest kernel. Some Linux distributions, for example Fedora, ship
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync a Linux kernel configured for a timer frequency of <emphasis
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync role="bold"> 1000Hz</emphasis>. We recommend to recompile the guest
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync kernel and to select a timer frequency of 100Hz.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Linux kernels shipped with Red Hat Enterprise Linux (RHEL) as of
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync release 4.7 and 5.1 as well as kernels of related Linux distributions
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync (for instance CentOS and Oracle Enterprise Linux) support a kernel
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync parameter <emphasis>divider=N</emphasis>. Hence, such kernels support a
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync lower timer frequency without recompilation. We suggest to add the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync kernel parameter <emphasis>divider=10</emphasis> to select a guest
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync kernel timer frequency of 100Hz.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Most Linux-based guests will fail with AMD Phenoms or
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync Barcelona-level Opterons due to a bug in the Linux kernel. Enable the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The following bugs in Linux kernels prevent them from executing
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync correctly in VirtualBox, causing VM boot crashes:<itemizedlist>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The Linux kernel version 2.6.18 (and some 2.6.17 versions)
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync introduced a race condition that can cause boot crashes in
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync VirtualBox. Please use a kernel version 2.6.19 or later.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>With hardware virtualization and the I/O APIC enabled,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync kernels before 2.6.24-rc6 may panic on boot with the following
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync message:<screen>Kernel panic - not syncing: IO-APIC + timer doesn't work! Boot with
6728a36898fd2be125a28e84d2115d19aa4923edvboxsyncapic=debug and send a report. Then try booting with the 'noapic' option</screen></para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>If you see this message, either disable hardware
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync virtualization or the I/O APIC (see <xref
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync linkend="settings-system" />), or upgrade the guest to a newer
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync kernel.<footnote>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync url="http://www.mail-archive.com/git-commits-head@vger.kernel.org/msg30813.html">http://www.mail-archive.com/git-commits-head@vger.kernel.org/msg30813.html</ulink>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync for details about the kernel fix.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>Shared clipboard, auto-resizing and seamless desktop in X11
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync guests</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Guest desktop services in guests running the X11 window system
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync (Solaris, Linux and others) are provided by a guest service called
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>VBoxClient</computeroutput>, which runs under the ID of
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the user who started the desktop session and is automatically started
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync using the following command lines <screen>VBoxClient --clipboard
6728a36898fd2be125a28e84d2115d19aa4923edvboxsyncVBoxClient --display
6728a36898fd2be125a28e84d2115d19aa4923edvboxsyncVBoxClient --seamless</screen> when your X11 user session is started if you
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync are using a common desktop environment (Gnome, KDE and others). If a
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync particular desktop service is not working correctly, it is worth
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync checking whether the process which should provide it is running.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The <computeroutput>VBoxClient</computeroutput> processes create
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync files in the user's home directory with names of the form
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>.vboxclient-*.pid</computeroutput> when they are running
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync in order to prevent a given service from being started twice. It can
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync happen due to misconfiguration that these files are created owned by
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync root and not deleted when the services are stopped, which will prevent
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync them from being started in future sessions. If the services cannot be
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync started, you may wish to check whether these files still exist.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>VBoxSVC out-of-process COM server issues</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>VirtualBox makes use of the Microsoft Component Object Model (COM)
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync for inter- and intra-process communication. This allows VirtualBox to
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync share a common configuration among different virtual machine processes
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync and provide several user interface options based on a common
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync architecture. All global status information and configuration is
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync maintained by the process <computeroutput>VBoxSVC.exe</computeroutput>,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync which is an out-of-process COM server. Whenever a VirtualBox process is
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync started, it requests access to the COM server and Windows automatically
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync starts the process. Note that it should never be started by the end
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync user.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>When the last process disconnects from the COM server, it will
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync terminate itself after some seconds. The VirtualBox configuration (XML
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync files) is maintained and owned by the COM server and the files are
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync locked whenever the server runs.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>In some cases - such as when a virtual machine is terminated
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync unexpectedly - the COM server will not notice that the client is
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync disconnected and stay active for a longer period (10 minutes or so)
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync keeping the configuration files locked. In other rare cases the COM
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync server might experience an internal error and subsequently other
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync processes fail to initialize it. In these situations, it is recommended
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync to use the Windows task manager to kill the process
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>VBoxSVC.exe</computeroutput>.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>In case you have assigned a physical CD/DVD drive to a guest and
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the guest does not notice when the medium changes, make sure that the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync Windows media change notification (MCN) feature is not turned off. This
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync is represented by the following key in the Windows registry:<screen><literal>HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Cdrom\Autorun</literal></screen>Certain
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync applications may disable this key against Microsoft's advice. If it is
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync set to 0, change it to 1 and reboot your system. VirtualBox relies on
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync Windows notifying it of media changes.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>Sluggish response when using Microsoft RDP client</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>If connecting to a Virtual Machine via the Microsoft RDP client
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync (called Remote Desktop Connection), there can be large delays between
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync input (moving the mouse over a menu is the most obvious situation) and
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync output. This is because this RDP client collects input for a certain
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync time before sending it to the RDP server.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The interval can be decreased by setting a Windows registry key to
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync smaller values than the default of 100. The key does not exist initially
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync and must be of type DWORD. The unit for its values is milliseconds.
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync Values around 20 are suitable for low-bandwidth connections between the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync RDP client and server. Values around 4 can be used for a gigabit
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync Ethernet connection. Generally values below 10 achieve a performance
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync that is very close to that of the local input devices and screen of the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync host on which the Virtual Machine is running.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Depending whether the setting should be changed for an individual
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync user or for the system, either</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <screen>HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\Min Send Interval</screen>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <screen>HKEY_LOCAL_MACHINE\Software\Microsoft\Terminal Server Client\Min Send Interval</screen>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>Running an iSCSI initiator and target on a single system</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Deadlocks can occur on a Windows host when attempting to access an
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync iSCSI target running in a guest virtual machine with an iSCSI initiator
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync (e.g. Microsoft iSCSI Initiator) that is running on the host. This is
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync caused by a flaw in the Windows cache manager component, and causes
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync sluggish host system response for several minutes, followed by a
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync "Delayed Write Failed" error message in the system tray or in a separate
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync message window. The guest is blocked during that period and may show
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync error messages or become unstable.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Setting the environment variable
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>VBOX_DISABLE_HOST_DISK_CACHE</computeroutput> to 1 will
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync enable a workaround for this problem until Microsoft addresses the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync issue. For example, open a command prompt window and start VirtualBox
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync like this:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <screen>set VBOX_DISABLE_HOST_DISK_CACHE=1
6728a36898fd2be125a28e84d2115d19aa4923edvboxsyncVirtualBox</screen>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>While this will decrease guest disk performance (especially
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync writes), it does not affect the performance of other applications
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync running on the host.</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>If no bridged adapters show up in the "Networking" section of the
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync VM settings, this typically means that the bridged networking driver was
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync not installed properly on your host. This could be due to the following
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync reasons: <itemizedlist>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>The maximum allowed filter count was reached on the host. In
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync this case, the MSI log would mention the
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <computeroutput>0x8004a029</computeroutput> error code returned on
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync NetFlt network component install:<screen>VBoxNetCfgWinInstallComponent: Install failed, hr (0x8004a029)</screen></para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>You can try to increase the maximum filter count in the
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync Windows registry at the following key:<screen>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network\MaxNumFilters</screen>The
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync maximum number allowed is 14. After a reboot, try to re-install
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync VirtualBox.</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync </listitem>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>The INF cache is corrupt. In this case, the install log
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync (<computeroutput>%windir%\inf\setupapi.log</computeroutput> on XP
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync or <computeroutput>%windir%\inf\setupapi.dev.log</computeroutput>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync on Vista or later) would typically mention the failure to find a
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync suitable driver package for either the
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <computeroutput>sun_VBoxNetFltmp</computeroutput> components. The
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync solution then is to uninstall VirtualBox, remove the INF cache
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync (<computeroutput>%windir%\inf\INFCACHE.1</computeroutput>), reboot
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync and try to re-install VirtualBox</para>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync </listitem>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <title>Host-only networking adapters cannot be created</title>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <para>If host-only adapter cannot be created (either via the Manager or
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync VBoxManage), then the INF cache is probably corrupt. In this case, the
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync install log (<computeroutput>%windir%\inf\setupapi.log</computeroutput>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync on XP or <computeroutput>%windir%\inf\setupapi.dev.log</computeroutput>
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync on Vista or later) would typically mention the failure to find a
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync suitable driver package for the
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync <computeroutput>sun_VBoxNetAdp</computeroutput> component. Again, as
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync with the bridged networking problem described above, the solution is to
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync uninstall VirtualBox, remove the INF cache
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync (<computeroutput>%windir%\inf\INFCACHE.1</computeroutput>), reboot and
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync try to re-install VirtualBox.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>If the VirtualBox kernel module
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync (<computeroutput>vboxdrv</computeroutput>) refuses to load, i.e. you get
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync an "Error inserting vboxdrv: Invalid argument", check (as root) the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync output of the <computeroutput>dmesg</computeroutput> command to find out
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync why the load failed. Most probably the kernel disagrees with the version
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync of the gcc used to compile the module. Make sure that you use the same
ac153c99053f1edf42b00bf3a13475923bc4fcf1vboxsync compiler as used to build the kernel.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>If you have configured a virtual machine to use the host's CD/DVD
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync drive, but this does not appear to work, make sure that the current user
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync has permission to access the corresponding Linux device file
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>/dev/cdrom</computeroutput> or similar). On most
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync distributions, the user must be added to a corresponding group (usually
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>Linux host CD/DVD drive not found (older distributions)</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>On older Linux distributions, if your CD/DVD device has a
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync different name, VirtualBox may be unable to find it. On older Linux
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync hosts, VirtualBox performs the following steps to locate your CD/DVD
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync drives:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>VirtualBox examines if the environment variable
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>VBOX_CDROM</computeroutput> is defined (see
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync below). If so, VirtualBox omits all the following checks.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>VirtualBox tests if
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>/dev/cdrom</computeroutput> works.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>In addition, VirtualBox checks if any CD/DVD drives are
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync currently mounted by checking
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>In addition, VirtualBox checks if any of the entries in
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>/etc/fstab</computeroutput> point to CD/DVD
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync devices.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync </listitem>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>In other words, you can try to set VBOX_CDROM to contain a list of
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync your CD/DVD devices, separated by colons, for example as follows:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><screen>export VBOX_CDROM='/dev/cdrom0:/dev/cdrom1'</screen>On
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync modern Linux distributions, VirtualBox uses the hardware abstraction
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync layer (hal) to locate CD and DVD hardware.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The previous instructions (for CD and DVD drives) apply
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync accordingly to floppy disks, except that on older distributions
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync VirtualBox tests for <computeroutput>/dev/fd*</computeroutput> devices
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync by default, and this can be overridden with the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>VBOX_FLOPPY</computeroutput> environment
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync variable.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>Strange guest IDE error messages when writing to CD/DVD</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>If the experimental CD/DVD writer support is enabled with an
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync incorrect VirtualBox, host or guest configuration, it is possible that
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync any attempt to access the CD/DVD writer fails and simply results in
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync guest kernel error messages (for Linux guests) or application error
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync messages (for Windows guests). VirtualBox performs the usual consistency
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync checks when a VM is powered up (in particular it aborts with an error
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync message if the device for the CD/DVD writer is not writable by the user
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync starting the VM), but it cannot detect all misconfigurations. The
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync necessary host and guest OS configuration is not specific for
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync VirtualBox, but a few frequent problems are listed here which occurred
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync in connection with VirtualBox.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Special care must be taken to use the correct device. The
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync configured host CD/DVD device file name (in most cases
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <literal>/dev/cdrom</literal>) must point to the device that allows
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync writing to the CD/DVD unit. For CD/DVD writer units connected to a SCSI
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync controller or to a IDE controller that interfaces to the Linux SCSI
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync subsystem (common for some SATA controllers), this must refer to the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync SCSI device node (e.g. <literal>/dev/scd0</literal>). Even for IDE
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync CD/DVD writer units this must refer to the appropriate SCSI CD-ROM
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync device node (e.g. <literal>/dev/scd0</literal>) if the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <literal>ide-scsi</literal> kernel module is loaded. This module is
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync required for CD/DVD writer support with all Linux 2.4 kernels and some
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync early 2.6 kernels. Many Linux distributions load this module whenever a
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync CD/DVD writer is detected in the system, even if the kernel would
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync support CD/DVD writers without the module. VirtualBox supports the use
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync of IDE device files (e.g. <literal>/dev/hdc</literal>), provided the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync kernel supports this and the <literal>ide-scsi</literal> module is not
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync loaded.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Similar rules (except that within the guest the CD/DVD writer is
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync always an IDE device) apply to the guest configuration. Since this setup
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync is very common, it is likely that the default configuration of the guest
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync works as expected.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>On Linux, VirtualBox makes use of a custom version of Mozilla
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync XPCOM (cross platform component object model) for inter- and
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync intra-process communication (IPC). The process
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>VBoxSVC</computeroutput> serves as a communication hub
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync between different VirtualBox processes and maintains the global
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync configuration, i.e. the XML database. When starting a VirtualBox
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync component, the processes <computeroutput>VBoxSVC</computeroutput> and
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>VirtualBoxXPCOMIPCD</computeroutput> are started
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync automatically. They are only accessible from the user account they are
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync running under. <computeroutput>VBoxSVC</computeroutput> owns the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync VirtualBox configuration database which normally resides in
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>~/.VirtualBox</computeroutput>. While it is running, the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync configuration files are locked. Communication between the various
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync VirtualBox components and <computeroutput>VBoxSVC</computeroutput> is
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync performed through a local domain socket residing in
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>/tmp/.vbox-<username>-ipc</computeroutput>. In
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync case there are communication problems (i.e. a VirtualBox application
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync cannot communicate with <computeroutput>VBoxSVC</computeroutput>),
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync terminate the daemons and remove the local domain socket
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync directory.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>If USB is not working on your Linux host, make sure that the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync current user is a member of the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>vboxusers</computeroutput> group. On older hosts, you
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync need to make sure that the user has permission to access the USB
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync filesystem (<computeroutput>usbfs</computeroutput>), which VirtualBox
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync relies on to retrieve valid information about your host's USB devices.
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync The rest of this section only applies to those older systems.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>As <computeroutput>usbfs</computeroutput> is a virtual filesystem,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>/proc/bus/usb</computeroutput> has no effect. The
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync permissions for <computeroutput>usbfs</computeroutput> can therefore
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <emphasis>only</emphasis> be changed by editing the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>/etc/fstab</computeroutput> file.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>For example, most Linux distributions have a user group called
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>usb</computeroutput> or similar, of which the current
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync user must be a member. To give all users of that group access to usbfs,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync make sure the following line is present:<screen># 85 is the USB group
6728a36898fd2be125a28e84d2115d19aa4923edvboxsyncnone /proc/bus/usb usbfs devgid=85,devmode=664 0 0</screen>Replace
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync 85 with the group ID that matches your system (search
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>/etc/group</computeroutput> for "usb" or similar).
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync Alternatively, if you don't mind the security hole, give all users
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync access to USB by changing "664" to "666".</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The various distributions are very creative from which script the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>usbfs</computeroutput> filesystem is mounted. Sometimes
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the command is hidden in unexpected places. For SuSE 10.0 the mount
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync command is part of the udev configuration file
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>/etc/udev/rules.d/50-udev.rules</computeroutput>. As
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync this distribution has no user group called
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>usb</computeroutput>, you may e.g. use the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>vboxusers</computeroutput> group which was created by
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the VirtualBox installer. Since group numbers are allocated dynamically,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the following example uses 85 as a placeholder. Modify the line
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync containing (a linebreak has been inserted to improve
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync readability)<screen>DEVPATH="/module/usbcore", ACTION=="add",
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync RUN+="/bin/mount -t usbfs usbfs /proc/bus/usb"</screen> and add the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync necessary options (make sure that everything is in a single
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync line):<screen>DEVPATH="/module/usbcore", ACTION=="add",
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync RUN+="/bin/mount -t usbfs usbfs /proc/bus/usb -o devgid=85,devmode=664"</screen></para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Debian Etch has the mount command in
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>/etc/init.d/mountkernfs.sh</computeroutput>. Since that
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync distribution has no group <computeroutput>usb</computeroutput>, it is
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync also the easiest solution to allow all members of the group
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>vboxusers</computeroutput> to access the USB subsystem.
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync Modify the line <screen>domount usbfs usbdevfs /proc/bus/usb -onoexec,nosuid,nodev</screen>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync so that it contains <screen>domount usbfs usbdevfs /proc/bus/usb -onoexec,nosuid,nodev,devgid=85,devmode=664</screen>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync As usual, replace the 85 with the actual group number which should get
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync access to USB devices.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Other distributions do similar operations in scripts stored in the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>/etc/init.d</computeroutput> directory.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Linux kernels including the grsec patch (see <literal><ulink
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync url="http://www.grsecurity.net/">http://www.grsecurity.net/</ulink></literal>)
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync and derivates have to disable PAX_MPROTECT for the VBox binaries to be
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync able to start a VM. The reason is that VBox has to create executable
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync code on anonymous memory.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>When running a large number of VMs with a lot of RAM on a Linux
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync system (say 20 VMs with 1GB of RAM each), additional VMs might fail to
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync start with a kernel error saying that the vmalloc pool is exhausted and
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync should be extended. The error message also tells you to specify
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <computeroutput>vmalloc=256MB</computeroutput> in your kernel parameter
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync list. If adding this parameter to your GRUB or LILO configuration makes
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the kernel fail to boot (with a weird error message such as "failed to
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync mount the root partition"), then you have probably run into a memory
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync conflict of your kernel and initial RAM disk. This can be solved by
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync adding the following parameter to your GRUB configuration:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>Cannot start VM, not enough contiguous memory</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>The ZFS file system is known to use all available RAM as cache if
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the default system settings are not changed. This may lead to a heavy
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync fragmentation of the host memory preventing VirtualBox VMs from being
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync started. We recommend to limit the ZFS cache by adding a line<screen>set zfs:zfs_arc_max = xxxx</screen>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync to /etc/system where <computeroutput>xxxx</computeroutput> bytes is the
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync amount of memory usable for the ZFS cache.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <title>VM aborts with out of memory errors on Solaris 10 hosts</title>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>32-bit Solaris 10 hosts (bug 1225025) require swap space equal to,
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync or greater than the host's physical memory size. For example, 8 GB
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync physical memory would require at least 8 GB swap. This can be configured
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync during a Solaris 10 install by choosing a 'custom install' and changing
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync the default partitions.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>This restriction applies only to 32-bit Solaris hosts, 64-bit
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync hosts are not affected!</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>For existing Solaris 10 installs, an additional swap image needs
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync to be mounted and used as swap. Hence if you have 1 GB swap and 8 GB of
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync physical memory, you require to add 7 GB more swap. This can be done as
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync follows:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para><screen>zfs create -V 8gb /_<ZFS volume>_/swap
6728a36898fd2be125a28e84d2115d19aa4923edvboxsyncswap -a /dev/zvol/dsk/_<ZFS volume>_/swap</screen></para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>To mount if after reboot, add the following line to
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <screen>/dev/zvol/dsk/_<ZFS volume>_/swap - - swap - no -</screen>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>Alternatively, you could grow the existing swap using:</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>And reboot the system for the changes to take effect.</para>
6728a36898fd2be125a28e84d2115d19aa4923edvboxsync <para>To mount it after reboot, add the following line to