rawdisk-access-disk-partitions.dita@ 98549

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1	<?xml version='1.0' encoding='UTF-8'?>
2	<!DOCTYPE topic PUBLIC "-//OASIS//DTD DITA Topic//EN" "topic.dtd">
3	<topic xml:lang="en-us" id="rawdisk-access-disk-partitions">
4	<title>Access to Individual Physical Hard Disk Partitions</title>
5
6	<body>
7	<p>
8	This <i>raw partition support</i> is quite
9	similar to the full hard disk access described above. However,
10	in this case, any partitioning information will be stored
11	inside the VMDK image. This means that you can install a
12	different boot loader in the virtual hard disk without
13	affecting the host's partitioning information. While the guest
14	will be able to <i>see</i> all partitions that
15	exist on the physical disk, access will be filtered in that
16	reading from partitions for which no access is allowed the
17	partitions will only yield zeroes, and all writes to them are
18	ignored.
19	</p>
20	<p>
21	To create a special image for raw partition support, which
22	will contain a small amount of data, on a Linux host, use the
23	command:
24	</p>
25	<pre xml:space="preserve">$ VBoxManage createmedium disk --filename <varname>path-to-file</varname>.vmdk --format=VMDK
26	--variant RawDisk --property RawDrive=/dev/sda --property Partitions=1,5</pre>
27	<p>
28	The command is identical to the one for full hard disk access,
29	except for the additional <codeph>--property</codeph>
30	Partitions=1,5 parameter. This example would create
31	the image
32	<filepath><varname>path-to-file</varname>.vmdk</filepath>,
33	which must be absolute, and partitions 1 and 5 of
34	<filepath>/dev/sda</filepath> would be made accessible to the
35	guest.
36	</p>
37	<p>
38	Oracle VM VirtualBox uses the same partition numbering as your Linux
39	host. As a result, the numbers given in the above example
40	would refer to the first primary partition and the first
41	logical drive in the extended partition, respectively.
42	</p>
43	<p>
44	On a Windows host, instead of the above device specification,
45	use for example <filepath>\\.\PhysicalDrive0</filepath>. On a
46	macOS host, instead of the above device specification use
47	<filepath>/dev/rdisk1</filepath>, for example. Note that on OS
48	X you can only use partitions which are not mounted. Unmount
49	the respective disk first using <i>diskutil unmountDisk
50	<filepath>/dev/diskX</filepath>
51	</i>. Partition numbers
52	are the same on Linux, Windows, and macOS hosts.
53	</p>
54	<p>
55	The numbers for the list of partitions can be taken from the
56	output of the following command:
57	</p>
58	<pre xml:space="preserve">$ VBoxManage list hostdrives</pre>
59	<p>
60	The output lists available drives and their partitions with
61	the partition types and sizes to give the user enough
62	information to identify the partitions necessary for the
63	guest.
64	</p>
65	<p>
66	Images which give access to individual partitions are specific
67	to a particular host disk setup. You cannot transfer these
68	images to another host. Also, whenever the host partitioning
69	changes, the image <i>must be recreated</i>.
70	</p>
71	<p>
72	Creating the image requires read/write access for the given
73	device. Read/write access is also later needed when using the
74	image from a virtual machine. If this is not feasible, there
75	is a special variant for raw partition access, currently only
76	available on Linux hosts, that avoids having to give the
77	current user access to the entire disk. To set up such an
78	image, use:
79	</p>
80	<pre xml:space="preserve">$ VBoxManage createmedium disk --filename <varname>path-to-file</varname>.vmdk --format=VMDK
81	--variant RawDisk --property RawDrive=/dev/sda --property Partitions=1,5
82	--property Relative=1</pre>
83	<p>
84	When used from a virtual machine, the image will then refer
85	not to the entire disk, but only to the individual partitions.
86	In this example, <filepath>/dev/sda1</filepath> and
87	<filepath>/dev/sda5</filepath>. As a consequence, read/write
88	access is only required for the affected partitions, not for
89	the entire disk. During creation however, read-only access to
90	the entire disk is required to obtain the partitioning
91	information.
92	</p>
93	<p>
94	In some configurations it may be necessary to change the MBR
95	code of the created image. For example, to replace the Linux
96	boot loader that is used on the host by another boot loader.
97	This enables for example the guest to boot directly to
98	Windows, while the host boots Linux from the "same" disk. For
99	this purpose the <codeph>--property-file</codeph>
100	BootSector=<varname>path-to-file-with-boot-sector</varname>
101	parameter is provided. It specifies a file name from which to
102	take the MBR code. The partition table is not modified at all,
103	so a MBR file from a system with totally different
104	partitioning can be used. An example of this is:
105	</p>
106	<pre xml:space="preserve">$ VBoxManage createmedium disk --filename <varname>path-to-file</varname>.vmdk --format=VMDK
107	--variant RawDisk --property RawDrive=/dev/sda --property Partitions=1,5
108	--property-file BootSector=winxp.mbr</pre>
109	<p>
110	The modified MBR will be stored inside the image, not on the
111	host disk.
112	</p>
113	<p>
114	The created image can be attached to a storage controller in a
115	VM configuration as usual.
116	</p>
117	</body>
118
119	</topic>

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