@@ -89,9 +89,9 @@ STEXI
ETEXI
DEF("resize", img_resize,
- "resize [--object objectdef] [--image-opts] [-q] filename [+ | -]size")
+ "resize [--object objectdef] [--image-opts] [-q] [--shrink] filename [+ | -]size")
STEXI
-@item resize [--object @var{objectdef}] [--image-opts] [-q] @var{filename} [+ | -]@var{size}
+@item resize [--object @var{objectdef}] [--image-opts] [-q] [--shrink] @var{filename} [+ | -]@var{size}
ETEXI
STEXI
@@ -65,6 +65,7 @@ enum {
OPTION_TARGET_IMAGE_OPTS = 263,
OPTION_SIZE = 264,
OPTION_PREALLOCATION = 265,
+ OPTION_SHRINK = 266,
};
typedef enum OutputFormat {
@@ -3437,6 +3438,7 @@ static int img_resize(int argc, char **argv)
},
};
bool image_opts = false;
+ bool shrink = false;
/* Remove size from argv manually so that negative numbers are not treated
* as options by getopt. */
@@ -3455,6 +3457,7 @@ static int img_resize(int argc, char **argv)
{"object", required_argument, 0, OPTION_OBJECT},
{"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
{"preallocation", required_argument, 0, OPTION_PREALLOCATION},
+ {"shrink", no_argument, 0, OPTION_SHRINK},
{0, 0, 0, 0}
};
c = getopt_long(argc, argv, ":f:hq",
@@ -3498,6 +3501,9 @@ static int img_resize(int argc, char **argv)
return 1;
}
break;
+ case OPTION_SHRINK:
+ shrink = true;
+ break;
}
}
if (optind != argc - 1) {
@@ -3571,6 +3577,23 @@ static int img_resize(int argc, char **argv)
goto out;
}
+ if (total_size < current_size && !shrink) {
+ warn_report("Shrinking an image will delete all data beyond the "
+ "shrunken image's end. Before performing such an "
+ "operation, make sure there is no important data there.");
+
+ if (g_strcmp0(bdrv_get_format_name(blk_bs(blk)), "raw") != 0) {
+ error_report(
+ "Use the --shrink option to perform a shrink operation.");
+ ret = -1;
+ goto out;
+ } else {
+ warn_report("Using the --shrink option will suppress this message."
+ "Note that future versions of qemu-img may refuse to "
+ "shrink images without this option.");
+ }
+ }
+
ret = blk_truncate(blk, total_size, prealloc, &err);
if (!ret) {
qprintf(quiet, "Image resized.\n");
@@ -536,7 +536,7 @@ qemu-img rebase -b base.img diff.qcow2
At this point, @code{modified.img} can be discarded, since
@code{base.img + diff.qcow2} contains the same information.
-@item resize [--preallocation=@var{prealloc}] @var{filename} [+ | -]@var{size}
+@item resize [--shrink] [--preallocation=@var{prealloc}] @var{filename} [+ | -]@var{size}
Change the disk image as if it had been created with @var{size}.
@@ -544,6 +544,10 @@ Before using this command to shrink a disk image, you MUST use file system and
partitioning tools inside the VM to reduce allocated file systems and partition
sizes accordingly. Failure to do so will result in data loss!
+When shrinking images, the @code{--shrink} option must be given. This informs
+qemu-img that the user acknowledges all loss of data beyond the truncated
+image's end.
+
After using this command to grow a disk image, you must use file system and
partitioning tools inside the VM to actually begin using the new space on the
device.
@@ -54,7 +54,7 @@ _make_test_img $IMG_SIZE
$QEMU_IO -c 'write 0 64k' "$TEST_IMG" | _filter_qemu_io
# Remove data cluster from image (first cluster: image header, second: reftable,
# third: refblock, fourth: L1 table, fifth: L2 table)
-$QEMU_IMG resize -f raw "$TEST_IMG" $((5 * 64 * 1024))
+$QEMU_IMG resize -f raw --shrink "$TEST_IMG" $((5 * 64 * 1024))
$QEMU_IO -c map "$TEST_IMG"
$QEMU_IMG map "$TEST_IMG"
@@ -69,7 +69,7 @@ $QEMU_IO -c 'write 0 64k' "$TEST_IMG" | _filter_qemu_io
qemu_comm_method=monitor _launch_qemu -drive if=none,file="$TEST_IMG",id=drv0
-$QEMU_IMG resize -f raw "$TEST_IMG" $((5 * 64 * 1024))
+$QEMU_IMG resize -f raw --shrink "$TEST_IMG" $((5 * 64 * 1024))
_send_qemu_cmd $QEMU_HANDLE 'qemu-io drv0 map' 'allocated' \
| sed -e 's/^(qemu).*qemu-io drv0 map...$/(qemu) qemu-io drv0 map/'