Developped expanding an NTFS volume downwards in ntfsresize

When the lower bound of an ntfs partition is moved down this patch
recreated new metadata in the expanded space without copying the
actual data. The existing code for moving the upper bound of the
partition has been kept unchanged.

ntfsprogs/ntfsresize.8.in

@@ -87,7 +87,11 @@ underlying partition. This can be done using
 .BR fdisk (8)
 by deleting the partition and recreating it with a larger size.
 Make sure it will not overlap with an other existing partition.
-Then  you may use
+You may enlarge upwards (first sector unchanged) or downwards (last
+sector unchanged), but you may not enlarge at both ends in a single step.
+If you merge two NTFS partitions, only one of them can be expanded to the
+merged partition.
+After you have enlarged the partition, you may use
 .B ntfsresize
 to enlarge the size of the filesystem.
 .SS Partitioning
@@ -122,8 +126,9 @@ is ready to be resized. If not, it will print any errors detected.
 If the device is fine, nothing will be printed.
 .TP
 \fB\-i\fR, \fB\-\-info\fR
-By using this option ntfsresize will determine the theoretically smallest
-shrunken filesystem size supported. Most of the time the result is the space
+By using this option without \fB\-\-expand\fP, ntfsresize will determine the
+theoretically smallest shrunken filesystem size supported.
+Most of the time the result is the space
 already used on the filesystem. Ntfsresize will refuse shrinking to a
 smaller size than what you got by this option and depending on several
 factors it might be unable to shrink very close to this theoretical
@@ -135,15 +140,23 @@ Practically the smallest shrunken size generally is
 at around "used space" + (20\-200 MB). Please also take into account
 that Windows might need about 50\-100 MB free space left to boot safely.
 
+If used in association with option \fB\-\-expand\fP, ntfsresize will determine
+the smallest downwards expansion size and the possible increments to the
+size. These are exact byte counts which must not be rounded.
+This option may be used after the partition has been expanded
+provided the upper bound has not been changed.
+
 This option never causes any changes to the filesystem, the partition is
 opened read\-only.
 .TP
 \fB\-m\fR, \fB\-\-info\-mb\-only\fR
 Like the info option, only print out the shrinkable size in MB.  Print nothing
 if the shrink size is the same as the original size (in MB).
+This option cannot be used in association with option \fB\-\-expand\fP.
 .TP
 \fB\-s\fR, \fB\-\-size\fR SIZE\fR[\fBk\fR|\fBM\fR|\fBG\fR]
-Resize filesystem to \fISIZE\fR[\fBk\fR|\fBM\fR|\fBG\fR] bytes.
+Resize filesystem to \fISIZE\fR[\fBk\fR|\fBM\fR|\fBG\fR] bytes by
+shifting its end and keeping its beginning unchanged.
 The optional modifiers
 .BR k ,
 .BR M ,
@@ -156,6 +169,23 @@ with
 .B \-\-no\-action
 first.
 .TP
+\fB\-x\fR, \fB\-\-expand\fR
+Expand the filesystem to the current partition size, shifting down its
+beginning and keeping its end unchanged. The metadata is recreated in the
+expanded space and no user data is relocated. This is incompatible with
+option \-s (or \-\-size) and can only be made if the expanded space is an
+exact multiple of the cluster size. It must also be large enough to hold the
+new metadata.
+
+If the expansion is interrupted for some reason (power outage, etc), you may
+restart the resizing, as the original data and metadata have been kept
+unchanged.
+
+Note : expanding a Windows system partition and filesystem downwards may lead
+to the registry or some files not matching the new system layout, or to
+some important files being located too far from the beginning of the
+partition, thus making Windows not bootable.
+.TP
 \fB\-f\fR, \fB\-\-force\fR
 Forces ntfsresize to proceed with the resize operation either without
 prompting for an explicit acceptance, or if the filesystem is marked for