[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);