(on older systems that don't have the L<fallocate(1)> command use
C<dd if=/dev/zero of=outdisk bs=1M count=..>)
+=head2 LOGICAL PARTITIONS
+
+Logical partitions (a.k.a. C</dev/sda5+> on disks using DOS partition
+tables) cannot be resized.
+
+To understand what is going on, firstly one of the four partitions
+C</dev/sda1-4> will have MBR partition type C<05> or C<0f>. This is
+called the B<extended partition>. Use L<virt-filesystems(1)> to see
+the MBR partition type.
+
+Logical partitions live inside the extended partition.
+
+The extended partition can be expanded, but not shrunk (unless you
+force it, which is not advisable). When the extended partition is
+copied across, all the logical partitions contained inside are copied
+over implicitly. Virt-resize does not look inside the extended
+partition, so it copies the logical partitions blindly.
+
+You cannot specify a logical partition (C</dev/sda5+>) at all on the
+command line. Doing so will give an error.
+
=head1 OPTIONS
=over 4
Display help.
+=item B<--align-first auto>
+
+=item B<--align-first never>
+
+=item B<--align-first always>
+
+Align the first partition for improved performance (see also the
+I<--alignment> option).
+
+The default is I<--align-first auto> which only aligns the first
+partition if it is safe to do so. That is, only when we know how to
+fix the bootloader automatically, and at the moment that can only be
+done for Windows guests.
+
+I<--align-first never> means we never move the first partition.
+This is the safest option. Try this if the guest does not boot
+after resizing.
+
+I<--align-first always> means we always align the first partition (if
+it needs to be aligned). For some guests this will break the
+bootloader, making the guest unbootable.
+
+=item B<--alignment N>
+
+Set the alignment of partitions to C<N> sectors. The default in
+virt-resize E<lt> 1.13.19 was 64 sectors, and after that is 128
+sectors.
+
+Assuming 512 byte sector size inside the guest, here are some
+suitable values for this:
+
+=over 4
+
+=item I<--alignment 1> (512 bytes)
+
+The partitions would be packed together as closely as possible, but
+would be completely unaligned. In some cases this can cause very poor
+performance. See L<virt-alignment-scan(1)> for further details.
+
+=item I<--alignment 8> (4K)
+
+This would be the minimum acceptable alignment for reasonable
+performance on modern hosts.
+
+=item I<--alignment 128> (64K)
+
+This alignment provides good performance when the host is using high
+end network storage.
+
+=item I<--alignment 2048> (1M)
+
+This is the standard alignment used by all newly installed guests
+since around 2008.
+
+=back
+
=item B<-d>
=item B<--debug>
=head2 "Partition 1 does not end on cylinder boundary."
-Virt-resize aligns partitions to multiples of 64 sectors. Usually
-this means the partitions will not be aligned to the ancient CHS
-geometry. However CHS geometry is meaningless for disks manufactured
-since the early 1990s, and doubly so for virtual hard drives.
-Alignment of partitions to cylinders is not required by any modern
-operating system.
+Virt-resize aligns partitions to multiples of 128 sectors (see the
+I<--alignment> parameter). Usually this means the partitions will not
+be aligned to the ancient CHS geometry. However CHS geometry is
+meaningless for disks manufactured since the early 1990s, and doubly
+so for virtual hard drives. Alignment of partitions to cylinders is
+not required by any modern operating system.
=head2 RESIZING WINDOWS VIRTUAL MACHINES
In Windows Vista and later versions, Microsoft switched to using a
separate boot partition. In these VMs, typically C</dev/sda1> is the
-boot partition and C</dev/sda2> is the main (C:) drive. We have not
-had any luck resizing the boot partition. Doing so seems to break the
-guest completely. However expanding the second partition (ie. C:
-drive) should work.
+boot partition and C</dev/sda2> is the main (C:) drive. Resizing the
+first (boot) partition causes the bootloader to fail with
+C<0xC0000225> error. Resizing the second partition (ie. C: drive)
+should work.
Windows may initiate a lengthy "chkdsk" on first boot after a resize,
if NTFS partitions have been expanded. This is just a safety check
=head2 GUEST BOOT STUCK AT "GRUB"
If a Linux guest does not boot after resizing, and the boot is stuck
-after printing C<GRUB> on the console, try reinstalling grub. This
-sometimes happens on older (RHEL 5-era) guests, for reasons we don't
-fully understand, although we think is to do with partition alignment.
+after printing C<GRUB> on the console, try reinstalling grub.
guestfish -i -a newdisk
><fs> cat /boot/grub/device.map
L<grub-install(8)>,
L<virt-rescue(1)>,
L<virt-sparsify(1)>,
+L<virt-alignment-scan(1)>,
L<http://libguestfs.org/>.
=head1 AUTHOR
git.annexia.org / libguestfs.git / blobdiff