[Qemu-devel] Converting installed windows (or ?) partition to virtual machine image

[Qemu-devel] Converting installed windows (or ?) partition to virtual machine image

[orion]

I'd like to try to convert the installed Windows partition of a dual boot
machine into a virtual machine image.  It seems like qemu-img currently
only supports copying an entire disk (/dev/sda for example) to a disk
image.  It would be nice if one could specify a single partition.

As a first hack/attempt to try this out, I'm trying the patch below
(against 0.9.1) to only copy a certain number of sectors.  Since the
Windows partition is almost always the first partition on the disk,
hopefully this will work for most folks.  I guess if you've already
installed grub you'll have issues unless you also include the /boot
partition.

It would be nice though to think about what it would take to do this
"right".   Seems like you could source from a single partition and
generate the proper MBR and partition table in the virtual machine image
without too much trouble.  A cursory glance seems to indicate that the
vvfat format does something like this.

Thoughts?

- Orion

--- qemu-0.9.1/qemu-img.c.part  2008-01-06 12:38:42.000000000 -0700
+++ qemu-0.9.1/qemu-img.c       2008-10-09 16:46:47.000000000 -0600
@@ -411,7 +411,7 @@
     const char *fmt, *out_fmt, *out_filename;
     BlockDriver *drv;
     BlockDriverState **bs, *out_bs;
-    int64_t total_sectors, nb_sectors, sector_num, bs_offset;
+    int64_t total_sectors, nb_sectors, sector_num, bs_offset,
requested_sectors = 0;
     uint64_t bs_sectors;
     uint8_t buf[IO_BUF_SIZE];
     const uint8_t *buf1;
@@ -421,7 +421,7 @@
     out_fmt = "raw";
     flags = 0;
     for(;;) {
-        c = getopt(argc, argv, "f:O:hce6");
+        c = getopt(argc, argv, "f:O:s:hce6");
         if (c == -1)
             break;
         switch(c) {
@@ -434,6 +434,9 @@
         case 'O':
             out_fmt = optarg;
             break;
+        case 's':
+            requested_sectors = atoll(optarg);
+            break;
         case 'c':
             flags |= BLOCK_FLAG_COMPRESS;
             break;
@@ -464,6 +467,9 @@
         total_sectors += bs_sectors;
     }

+    if (requested_sectors)
+        total_sectors = requested_sectors;
+
     drv = bdrv_find_format(out_fmt);
     if (!drv)
         error("Unknown file format '%s'", out_fmt);

Re: [Qemu-devel] Converting installed windows (or ?) partition to virtual machine image

[Johannes Schindelin]

Hi,

On Thu, 9 Oct 2008, orion@cora.nwra.com wrote:

> I'd like to try to convert the installed Windows partition of a dual 
> boot machine into a virtual machine image.  It seems like qemu-img 
> currently only supports copying an entire disk (/dev/sda for example) to 
> a disk image.  It would be nice if one could specify a single partition.
> 
> As a first hack/attempt to try this out, I'm trying the patch below 
> (against 0.9.1) to only copy a certain number of sectors.  Since the 
> Windows partition is almost always the first partition on the disk, 
> hopefully this will work for most folks.  I guess if you've already 
> installed grub you'll have issues unless you also include the /boot 
> partition.

I think a better method would be to do something like this:

	(dd if=/dev/zero bs=32256 count=1 && dd if=/dev/sda1) > disk.img

and then adding one partition with "fdisk disk.img".  The 32256 is what is 
commonly reserved before the first partition (this is where the mbr and 
boot sector viruses live).

> It would be nice though to think about what it would take to do this
> "right".   Seems like you could source from a single partition and
> generate the proper MBR and partition table in the virtual machine image
> without too much trouble.  A cursory glance seems to indicate that the
> vvfat format does something like this.

vvfat does something completely different.  It takes an existing directory 
structure and simulates a VFAT partition from that, no matter what the 
original file system was.

Ciao,
Dscho

Re: [Qemu-devel] Converting installed windows (or ?) partition to virtual machine image

[andrzej zaborowski]

2008/10/10 Johannes Schindelin <Johannes.Schindelin@gmx.de>:
> On Thu, 9 Oct 2008, orion@cora.nwra.com wrote:
>> It would be nice though to think about what it would take to do this
>> "right".   Seems like you could source from a single partition and
>> generate the proper MBR and partition table in the virtual machine image
>> without too much trouble.  A cursory glance seems to indicate that the
>> vvfat format does something like this.
>
> vvfat does something completely different.  It takes an existing directory
> structure and simulates a VFAT partition from that, no matter what the
> original file system was.

It simulates a filesystem and it simulates a whole disk with a valid
partition table and one partition in it, so yes, it does what is
wanted and it shouldn't be hard to replace the part that simulates the
filesystem with an existing partition or file.

Cheers