| 1 | <?xml version='1.0' encoding='UTF-8'?>
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| 2 | <!DOCTYPE topic PUBLIC "-//OASIS//DTD DITA Topic//EN" "topic.dtd">
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| 3 | <topic xml:lang="en-us" id="technical-components">
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| 4 | <title>Oracle VM VirtualBox Executables and Components</title>
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| 5 |
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| 6 | <body>
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| 7 | <p>
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| 8 | Oracle VM VirtualBox was designed to be modular and flexible. When the
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| 9 | Oracle VM VirtualBox graphical user interface (GUI) is opened and a VM
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| 10 | is started, at least the following three processes are running:
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| 11 | </p>
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| 12 | <ul>
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| 13 | <li>
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| 14 | <p><userinput>VBoxSVC</userinput>, the Oracle VM VirtualBox service process
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| 15 | which always runs in the background. This process is started
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| 16 | automatically by the first Oracle VM VirtualBox client process and
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| 17 | exits a short time after the last client exits. The first
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| 18 | Oracle VM VirtualBox service can be VirtualBox Manager,
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| 19 | <userinput>VBoxManage</userinput>,
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| 20 | <userinput>VBoxHeadless</userinput>, the web service amongst
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| 21 | others. The service is responsible for bookkeeping,
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| 22 | maintaining the state of all VMs, and for providing
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| 23 | communication between Oracle VM VirtualBox components. This
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| 24 | communication is implemented using COM/XPCOM.
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| 25 | </p>
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| 26 | <note>
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| 27 | <p>
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| 28 | When we refer to <i>clients</i> here, we mean
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| 29 | the local clients of a particular <userinput>VBoxSVC</userinput>
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| 30 | server process, not clients in a network. Oracle VM VirtualBox
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| 31 | employs its own client/server design to allow its processes
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| 32 | to cooperate, but all these processes run under the same
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| 33 | user account on the host operating system, and this is
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| 34 | totally transparent to the user.
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| 35 | </p>
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| 36 | </note>
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| 37 | </li>
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| 38 | <li>
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| 39 | <p>
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| 40 | The GUI process, <userinput>VirtualBoxVM</userinput>, a client
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| 41 | application based on the cross-platform Qt library. When
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| 42 | started without the <codeph>--startvm</codeph> option, this
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| 43 | application acts as VirtualBox Manager, displaying the VMs and their
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| 44 | settings. It then communicates settings and state changes to
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| 45 | <userinput>VBoxSVC</userinput> and also reflects changes effected
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| 46 | through other means, such as the <userinput>VBoxManage</userinput>
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| 47 | command.
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| 48 | </p>
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| 49 | </li>
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| 50 | <li>
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| 51 | <p>
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| 52 | If the <userinput>VirtualBoxVM</userinput> client application is
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| 53 | started with the <codeph>--startvm</codeph> argument, it loads
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| 54 | the VMM library which includes the actual hypervisor and then
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| 55 | runs a virtual machine and provides the input and output for
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| 56 | the guest.
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| 57 | </p>
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| 58 | </li>
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| 59 | </ul>
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| 60 | <p>
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| 61 | Any Oracle VM VirtualBox front-end, or client, will communicate with the
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| 62 | service process and can both control and reflect the current
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| 63 | state. For example, either the VM selector or the VM window or
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| 64 | VBoxManage can be used to pause the running VM, and other
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| 65 | components will always reflect the changed state.
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| 66 | </p>
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| 67 | <p>
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| 68 | The Oracle VM VirtualBox GUI application, called VirtualBox Manager, is only one
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| 69 | of several available front ends, or clients. The complete list
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| 70 | shipped with Oracle VM VirtualBox is as follows:
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| 71 | </p>
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| 72 | <ul>
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| 73 | <li>
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| 74 | <p><userinput>VirtualBoxVM</userinput>: The Qt front end implementing
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| 75 | VirtualBox Manager and running VMs.
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| 76 | </p>
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| 77 | </li>
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| 78 | <li>
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| 79 | <p><userinput>VBoxManage</userinput>: A less user-friendly but more
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| 80 | powerful alternative. See <xref href="vboxmanage.dita">VBoxManage</xref>.
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| 81 | </p>
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| 82 | </li>
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| 83 | <li>
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| 84 | <p><userinput>VBoxHeadless</userinput>: A VM front end which does not
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| 85 | directly provide any video output and keyboard or mouse input,
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| 86 | but enables redirection through the VirtualBox Remote Desktop
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| 87 | Extension. See <xref href="vboxheadless.dita"/>.
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| 88 | </p>
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| 89 | </li>
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| 90 | <li>
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| 91 | <p><userinput>vboxwebsrv</userinput>: The Oracle VM VirtualBox web service
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| 92 | process which enables control of an Oracle VM VirtualBox host
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| 93 | remotely. This is described in detail in the Oracle VM VirtualBox
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| 94 | Software Development Kit (SDK) reference. See
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| 95 | <xref href="VirtualBoxAPI.dita"/>.
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| 96 | </p>
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| 97 | </li>
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| 98 | <li>
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| 99 | <p>
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| 100 | The Oracle VM VirtualBox Python shell: A Python alternative to
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| 101 | <userinput>VBoxManage</userinput>. This is also described in the
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| 102 | SDK reference.
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| 103 | </p>
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| 104 | </li>
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| 105 | </ul>
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| 106 | <p>
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| 107 | Internally, Oracle VM VirtualBox consists of many more or less separate
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| 108 | components. You may encounter these when analyzing Oracle VM VirtualBox
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| 109 | internal error messages or log files. These include the following:
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| 110 | </p>
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| 111 | <ul>
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| 112 | <li>
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| 113 | <p>
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| 114 | IPRT: A portable runtime library which abstracts file access,
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| 115 | threading, and string manipulation. Whenever Oracle VM VirtualBox
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| 116 | accesses host operating features, it does so through this
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| 117 | library for cross-platform portability.
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| 118 | </p>
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| 119 | </li>
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| 120 | <li>
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| 121 | <p>
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| 122 | VMM (Virtual Machine Monitor): The heart of the hypervisor.
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| 123 | </p>
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| 124 | </li>
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| 125 | <li>
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| 126 | <p>
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| 127 | EM (Execution Manager): Controls execution of guest code.
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| 128 | </p>
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| 129 | </li>
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| 130 | <li>
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| 131 | <p>
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| 132 | TRPM (Trap Manager): Intercepts and processes guest traps and
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| 133 | exceptions.
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| 134 | </p>
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| 135 | </li>
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| 136 | <li>
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| 137 | <p>
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| 138 | HM (Hardware Acceleration Manager): Provides support for VT-x
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| 139 | and AMD-V.
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| 140 | </p>
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| 141 | </li>
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| 142 | <li>
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| 143 | <p>
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| 144 | GIM (Guest Interface Manager): Provides support for various
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| 145 | paravirtualization interfaces to the guest.
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| 146 | </p>
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| 147 | </li>
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| 148 | <li>
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| 149 | <p>
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| 150 | PDM (Pluggable Device Manager): An abstract interface between
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| 151 | the VMM and emulated devices which separates device
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| 152 | implementations from VMM internals and makes it easy to add
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| 153 | new emulated devices. Through PDM, third-party developers can
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| 154 | add new virtual devices to Oracle VM VirtualBox without having to
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| 155 | change Oracle VM VirtualBox itself.
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| 156 | </p>
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| 157 | </li>
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| 158 | <li>
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| 159 | <p>
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| 160 | PGM (Page Manager): A component that controls guest paging.
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| 161 | </p>
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| 162 | </li>
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| 163 | <li>
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| 164 | <p>
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| 165 | TM (Time Manager): Handles timers and all aspects of time
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| 166 | inside guests.
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| 167 | </p>
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| 168 | </li>
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| 169 | <li>
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| 170 | <p>
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| 171 | CFGM (Configuration Manager): Provides a tree structure which
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| 172 | holds configuration settings for the VM and all emulated
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| 173 | devices.
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| 174 | </p>
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| 175 | </li>
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| 176 | <li>
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| 177 | <p>
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| 178 | SSM (Saved State Manager): Saves and loads VM state.
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| 179 | </p>
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| 180 | </li>
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| 181 | <li>
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| 182 | <p>
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| 183 | VUSB (Virtual USB): A USB layer which separates emulated USB
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| 184 | controllers from the controllers on the host and from USB
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| 185 | devices. This component also enables remote USB.
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| 186 | </p>
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| 187 | </li>
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| 188 | <li>
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| 189 | <p>
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| 190 | DBGF (Debug Facility): A built-in VM debugger.
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| 191 | </p>
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| 192 | </li>
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| 193 | <li>
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| 194 | <p>
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| 195 | Oracle VM VirtualBox emulates a number of devices to provide the
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| 196 | hardware environment that various guests need. Most of these
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| 197 | are standard devices found in many PC compatible machines and
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| 198 | widely supported by guest operating systems. For network and
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| 199 | storage devices in particular, there are several options for
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| 200 | the emulated devices to access the underlying hardware. These
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| 201 | devices are managed by PDM.
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| 202 | </p>
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| 203 | </li>
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| 204 | <li>
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| 205 | <p>
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| 206 | Guest Additions for various guest operating systems. This is
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| 207 | code that is installed from within a virtual machine. See
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| 208 | <xref href="guestadditions.dita">Guest Additions</xref>.
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| 209 | </p>
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| 210 | </li>
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| 211 | <li>
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| 212 | <p>
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| 213 | The "Main" component is special. It ties all the above bits
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| 214 | together and is the only public API that Oracle VM VirtualBox
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| 215 | provides. All the client processes listed above use only this
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| 216 | API and never access the hypervisor components directly. As a
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| 217 | result, third-party applications that use the Oracle VM VirtualBox
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| 218 | Main API can rely on the fact that it is always well-tested
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| 219 | and that all capabilities of Oracle VM VirtualBox are fully exposed.
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| 220 | It is this API that is described in the Oracle VM VirtualBox SDK.
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| 221 | See <xref href="VirtualBoxAPI.dita#VirtualBoxAPI"/>.
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| 222 | </p>
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| 223 | </li>
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| 224 | </ul>
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| 225 | </body>
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| 226 |
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| 227 | </topic>
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