libguestfs/tools/virt-resize

#!/usr/bin/perl -w
# virt-resize
# Copyright (C) 2010 Red Hat Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

use warnings;
use strict;

use Sys::Guestfs;
use Sys::Guestfs::Lib qw(feature_available);
use Fcntl qw(S_ISREG SEEK_SET);
use POSIX qw(floor);
use Pod::Usage;
use Getopt::Long;
use Data::Dumper;
use Locale::TextDomain 'libguestfs';

$Data::Dumper::Sortkeys = 1;

die __"virt-resize: sorry this program does not work on a 32 bit host\n"
    if ~1 == 4294967294;

$| = 1;

=encoding utf8

=head1 NAME

virt-resize - Resize a virtual machine disk

=head1 SYNOPSIS

 virt-resize [--resize /dev/sdaN=[+/-]<size>[%]]
   [--expand /dev/sdaN] [--shrink /dev/sdaN]
   [--ignore /dev/sdaN] [--delete /dev/sdaN] [...] indisk outdisk

=head1 DESCRIPTION

Virt-resize is a tool which can resize a virtual machine disk, making
it larger or smaller overall, and resizing or deleting any partitions
contained within.

Virt-resize B<cannot> resize disk images in-place.  Virt-resize
B<should not> be used on live virtual machines - for consistent
results, shut the virtual machine down before resizing it.

If you are not familiar with the associated tools:
L<virt-filesystems(1)> and L<virt-df(1)>, we recommend you go and read
those manual pages first.

=head1 EXAMPLES

Copy C<olddisk> to C<newdisk>, extending one of the guest's partitions
to fill the extra 5GB of space.

 truncate -r olddisk newdisk; truncate -s +5G newdisk
 virt-filesystems --long -h --all -a olddisk
 # Note "/dev/sda2" is a partition inside the "olddisk" file.
 virt-resize --expand /dev/sda2 olddisk newdisk

As above, but make the /boot partition 200MB bigger, while giving the
remaining space to /dev/sda2:

 virt-resize --resize /dev/sda1=+200M --expand /dev/sda2 olddisk newdisk

As above, but the output format will be uncompressed qcow2:

 qemu-img create -f qcow2 newdisk.qcow2 15G
 virt-resize --expand /dev/sda2 olddisk newdisk.qcow2

=head1 DETAILED USAGE

=head2 EXPANDING A VIRTUAL MACHINE DISK

=over 4

=item 1. Shut down the virtual machine

=item 2. Locate input disk image

Locate the input disk image (ie. the file or device on the host
containing the guest's disk).  If the guest is managed by libvirt, you
can use C<virsh dumpxml> like this to find the disk image name:

 # virsh dumpxml guestname | xpath /domain/devices/disk/source
 Found 1 nodes:
 -- NODE --
 <source dev="/dev/vg/lv_guest" />

=item 3. Look at current sizing

Use L<virt-filesystems(1)> to display the current partitions and
sizes:

 # virt-filesystems --long --parts --blkdevs -h -a /dev/vg/lv_guest
 Name       Type       Size  Parent
 /dev/sda1  partition  101M  /dev/sda
 /dev/sda2  partition  7.9G  /dev/sda
 /dev/sda   device     8.0G  -

(This example is a virtual machine with an 8 GB disk which we would
like to expand up to 10 GB).

=item 4. Create output disk

Virt-resize cannot do in-place disk modifications.  You have to have
space to store the resized output disk.

To store the resized disk image in a file, create a file of a suitable
size:

 # rm -f outdisk
 # truncate -s 10G outdisk

Or use L<lvcreate(1)> to create a logical volume:

 # lvcreate -L 10G -n lv_name vg_name

Or use L<virsh(1)> vol-create-as to create a libvirt storage volume:

 # virsh pool-list
 # virsh vol-create-as poolname newvol 10G

=item 5. Resize

virt-resize takes two mandatory parameters, the input disk (eg. device
or file) and the output disk.  The output disk is the one created in
the previous step.

 # virt-resize indisk outdisk

This command just copies disk image C<indisk> to disk image C<outdisk>
I<without> resizing or changing any existing partitions.  If
C<outdisk> is larger, then an extra, empty partition is created at the
end of the disk covering the extra space.  If C<outdisk> is smaller,
then it will give an error.

More realistically you'd want to expand existing partitions in the
disk image by passing extra options (for the full list see the
L</OPTIONS> section below).

L</--expand> is the most useful option.  It expands the named
partition within the disk to fill any extra space:

 # virt-resize --expand /dev/sda2 indisk outdisk

(In this case, an extra partition is I<not> created at the end of the
disk, because there will be no unused space).

L</--resize> is the other commonly used option.  The following would
increase the size of /dev/sda1 by 200M, and expand /dev/sda2
to fill the rest of the available space:

 # virt-resize --resize /dev/sda1=+200M --expand /dev/sda2 \
     indisk outdisk

If the expanded partition in the image contains a filesystem or LVM
PV, then if virt-resize knows how, it will resize the contents, the
equivalent of calling a command such as L<pvresize(8)>,
L<resize2fs(8)> or L<ntfsresize(8)>.  However virt-resize does not
know how to resize some filesystems, so you would have to online
resize them after booting the guest.

Other options are covered below.

=item 6. Test

Thoroughly test the new disk image I<before> discarding the old one.

If you are using libvirt, edit the XML to point at the new disk:

 # virsh edit guestname

Change E<lt>source ...E<gt>, see
L<http://libvirt.org/formatdomain.html#elementsDisks>

Then start up the domain with the new, resized disk:

 # virsh start guestname

and check that it still works.  See also the L</NOTES> section below
for additional information.

=item 7. Resize LVs etc inside the guest

(This can also be done offline using L<guestfish(1)>)

Once the guest has booted you should see the new space available, at
least for filesystems that virt-resize knows how to resize, and for
PVs.  The user may need to resize LVs inside PVs, and also resize
filesystem types that virt-resize does not know how to expand.

=back

=head2 SHRINKING A VIRTUAL MACHINE DISK

Shrinking is somewhat more complex than expanding, and only an
overview is given here.

Firstly virt-resize will not attempt to shrink any partition content
(PVs, filesystems).  The user has to shrink content before passing the
disk image to virt-resize, and virt-resize will check that the content
has been shrunk properly.

(Shrinking can also be done offline using L<guestfish(1)>)

After shrinking PVs and filesystems, shut down the guest, and proceed
with steps 3 and 4 above to allocate a new disk image.

Then run virt-resize with any of the C<--shrink> and/or C<--resize>
options.

=head2 IGNORING OR DELETING PARTITIONS

virt-resize also gives a convenient way to ignore or delete partitions
when copying from the input disk to the output disk.  Ignoring a
partition speeds up the copy where you don't care about the existing
contents of a partition.  Deleting a partition removes it completely,
but note that it also renumbers any partitions after the one which is
deleted, which can leave some guests unbootable.

=head2 QCOW2 AND NON-SPARSE RAW FORMATS

If the input disk is in qcow2 format, then you may prefer that the
output is in qcow2 format as well.  Alternately, virt-resize can
convert the format on the fly.  The output format is simply determined
by the format of the empty output container that you provide.  Thus to
create qcow2 output, use:

 qemu-img create [-c] -f qcow2 outdisk [size]

instead of the truncate command (use C<-c> for a compressed disk).

Similarly, to get non-sparse raw output use:

 fallocate -l size outdisk

(on older systems that don't have the L<fallocate(1)> command use
C<dd if=/dev/zero of=outdisk bs=1M count=..>)

=head1 OPTIONS

=over 4

=cut

my $help;

=item B<--help>

Display help.

=cut

my $version;

=item B<--version>

Display version number and exit.

=cut

my @resize;

=item B<--resize part=size>

Resize the named partition (expanding or shrinking it) so that it has
the given size.

C<size> can be expressed as an absolute number followed by
b/K/M/G/T/P/E to mean bytes, Kilobytes, Megabytes, Gigabytes,
Terabytes, Petabytes or Exabytes; or as a percentage of the current
size; or as a relative number or percentage.  For example:

 --resize /dev/sda2=10G

 --resize /dev/sda4=90%

 --resize /dev/sda2=+1G

 --resize /dev/sda2=-200M

 --resize /dev/sda1=+128K

 --resize /dev/sda1=+10%

 --resize /dev/sda1=-10%

You can increase the size of any partition.  Virt-resize will expand
the direct content of the partition if it knows how (see C<--expand>
below).

You can only I<decrease> the size of partitions that contain
filesystems or PVs which have already been shrunk.  Virt-resize will
check this has been done before proceeding, or else will print an
error (see also C<--resize-force>).

You can give this option multiple times.

=cut

my @resize_force;

=item B<--resize-force part=size>

This is the same as C<--resize> except that it will let you decrease
the size of any partition.  Generally this means you will lose any
data which was at the end of the partition you shrink, but you may not
care about that (eg. if shrinking an unused partition, or if you can
easily recreate it such as a swap partition).

See also the C<--ignore> option.

=cut

my $expand;

=item B<--expand part>

Expand the named partition so it uses up all extra space (space left
over after any other resize changes that you request have been done).

If virt-resize knows how, it will expand the direct content of the
partition.  For example, if the partition is an LVM PV, it will expand
the PV to fit (like calling L<pvresize(8)>).  Virt-resize leaves any
other content it doesn't know about alone.

Currently virt-resize can resize:

=over 4

=item *

ext2, ext3 and ext4 filesystems when they are contained
directly inside a partition.

=item *

NTFS filesystems contained directly in a partition, if libguestfs was
compiled with support for NTFS.

The filesystem must have been shut down consistently last time it was
used.  Additionally, L<ntfsresize(8)> marks the resized filesystem as
requiring a consistency check, so at the first boot after resizing
Windows will check the disk.

=item *

LVM PVs (physical volumes).  virt-resize does not usually resize
anything inside the PV, but see the C<--LV-expand> option.  The user
could also resize LVs as desired after boot.

=back

Note that you cannot use C<--expand> and C<--shrink> together.

=cut

my $shrink;

=item B<--shrink part>

Shrink the named partition until the overall disk image fits in the
destination.  The named partition B<must> contain a filesystem or PV
which has already been shrunk using another tool (eg. L<guestfish(1)>
or other online tools).  Virt-resize will check this and give an error
if it has not been done.

The amount by which the overall disk must be shrunk (after carrying
out all other operations requested by the user) is called the
"deficit".  For example, a straight copy (assume no other operations)
from a 5GB disk image to a 4GB disk image results in a 1GB deficit.
In this case, virt-resize would give an error unless the user
specified a partition to shrink and that partition had more than a
gigabyte of free space.

Note that you cannot use C<--expand> and C<--shrink> together.

=cut

my @ignore;

=item B<--ignore part>

Ignore the named partition.  Effectively this means the partition is
allocated on the destination disk, but the content is not copied
across from the source disk.  The content of the partition will be
blank (all zero bytes).

You can give this option multiple times.

=cut

my @delete;

=item B<--delete part>

Delete the named partition.  It would be more accurate to describe
this as "don't copy it over", since virt-resize doesn't do in-place
changes and the original disk image is left intact.

Note that when you delete a partition, then anything contained in the
partition is also deleted.  Furthermore, this causes any partitions
that come after to be I<renumbered>, which can easily make your guest
unbootable.

You can give this option multiple times.

=cut

my @lv_expand;

=item B<--LV-expand logvol>

This takes the logical volume and, as a final step, expands it to fill
all the space available in its volume group.  A typical usage,
assuming a Linux guest with a single PV C</dev/sda2> and a root device
called C</dev/vg_guest/lv_root> would be:

 virt-resize indisk outdisk \
   --expand /dev/sda2 --LV-expand /dev/vg_guest/lv_root

This would first expand the partition (and PV), and then expand the
root device to fill the extra space in the PV.

The contents of the LV are also resized if virt-resize knows how to do
that.  You can stop virt-resize from trying to expand the content by
using the option C<--no-expand-content>.

Use L<virt-filesystems(1)> to list the filesystems in
the guest.

You can give this option multiple times, I<but> it doesn't
make sense to do this unless the logical volumes you specify
are all in different volume groups.

=cut

my $copy_boot_loader = 1;

=item B<--no-copy-boot-loader>

By default, virt-resize copies over some sectors at the start of the
disk (up to the beginning of the first partition).  Commonly these
sectors contain the Master Boot Record (MBR) and the boot loader, and
are required in order for the guest to boot correctly.

If you specify this flag, then this initial copy is not done.  You may
need to reinstall the boot loader in this case.

=cut

my $extra_partition = 1;
my $min_extra_partition = 10 * 1024 * 1024; # see below

=item B<--no-extra-partition>

By default, virt-resize creates an extra partition if there is any
extra, unused space after all resizing has happened.  Use this option
to prevent the extra partition from being created.  If you do this
then the extra space will be inaccessible until you run fdisk, parted,
or some other partitioning tool in the guest.

Note that if the surplus space is smaller than 10 MB, no extra
partition will be created.

=cut

my $expand_content = 1;

=item B<--no-expand-content>

By default, virt-resize will try to expand the direct contents
of partitions, if it knows how (see C<--expand> option above).

If you give the C<--no-expand-content> option then virt-resize
will not attempt this.

=cut

my $debug;

=item B<-d> | B<--debug>

Enable debugging messages.

=cut

my $dryrun;

=item B<-n> | B<--dryrun>

Print a summary of what would be done, but don't do anything.

=cut

my $quiet;

=item B<-q> | B<--quiet>

Don't print the summary.

=cut

my $format;

=item B<--format> raw

Specify the format of the input disk image.  If this flag is not
given then it is auto-detected from the image itself.

If working with untrusted raw-format guest disk images, you should
ensure the format is always specified.

Note that this option I<does not> affect the output format.
See L</QCOW2 AND NON-SPARSE RAW FORMATS>.

=cut

my $output_format;

=item B<--output-format> raw

Specify the format of the output disk image.  If this flag is not
given then it is auto-detected from the image itself.

If working with untrusted raw-format guest disk images, you should
ensure the format is always specified.

Note that you still need to create the output disk with the right
format.  See L</QCOW2 AND NON-SPARSE RAW FORMATS>.

=back

=cut

GetOptions ("help|?" => \$help,
            "version" => \$version,
            "resize=s" => \@resize,
            "resize-force=s" => \@resize_force,
            "expand=s" => \$expand,
            "shrink=s" => \$shrink,
            "ignore=s" => \@ignore,
            "delete=s" => \@delete,
            "lv-expand=s" => \@lv_expand,
            "copy-boot-loader!" => \$copy_boot_loader,
            "extra-partition!" => \$extra_partition,
            "expand-content!" => \$expand_content,
            "d|debug" => \$debug,
            "n|dryrun|dry-run" => \$dryrun,
            "q|quiet" => \$quiet,
            "format=s" => \$format,
            "output-format=s" => \$output_format,
    ) or pod2usage (2);
pod2usage (1) if $help;
if ($version) {
    my $g = Sys::Guestfs->new ();
    my %h = $g->version ();
    print "$h{major}.$h{minor}.$h{release}$h{extra}\n";
    exit
}

die "virt-resize [--options] indisk outdisk\n" unless @ARGV == 2;

# Check in and out images exist.
my $infile = $ARGV[0];
my $outfile = $ARGV[1];
die __x("virt-resize: {file}: does not exist or is not readable\n", file => $infile)
    unless -r $infile;
die __x("virt-resize: {file}: does not exist or is not writable\nYou have to create the destination disk before running this program.\nPlease read the virt-resize(1) manpage for more information.\n", file => $outfile)
    unless -w $outfile;

# Add them to the handle and launch the appliance.
my $g;
launch_guestfs ();

sub launch_guestfs
{
    $g = Sys::Guestfs->new ();
    $g->set_trace (1) if $debug;
    my @args = ($infile);
    push @args, readonly => 1;
    push @args, format => $format if defined $format;
    $g->add_drive_opts (@args);
    @args = ($outfile);
    push @args, format => $output_format if defined $output_format;
    $g->add_drive_opts (@args);
    $g->set_progress_callback (\&progress_callback) unless $quiet;
    $g->launch ();
}

my $sectsize = $g->blockdev_getss ("/dev/sdb");

# Get the size in bytes of each disk.
#
# Originally we computed this by looking at the same of the host file,
# but of course this failed for qcow2 images (RHBZ#633096).  The right
# way to do it is with $g->blockdev_getsize64.
my $insize = $g->blockdev_getsize64 ("/dev/sda");
my $outsize = $g->blockdev_getsize64 ("/dev/sdb");

if ($debug) {
    print "$infile size $insize bytes\n";
    print "$outfile size $outsize bytes\n";
}

# Create a partition table.
#
# We *must* do this before copying the bootloader across, and copying
# the bootloader must be careful not to disturb this partition table
# (RHBZ#633766).  There are two reasons for this:
#
# (1) The 'parted' library is stupid and broken.  In many ways.  In
# this particular instance the stupid and broken bit is that it
# overwrites the whole boot sector when initializating a partition
# table.  (Upstream don't consider this obvious problem to be a bug).
#
# (2) GPT has a backup partition table located at the end of the disk.
# It's non-movable, because the primary GPT contains fixed references
# to both the size of the disk and the backup partition table at the
# end.  This would be a problem for any resize that didn't either
# carefully move the backup GPT (and rewrite those references) or
# recreate the whole partition table from scratch.

my $parttype;
create_partition_table ();

sub create_partition_table
{
    local $_;

    $parttype = $g->part_get_parttype ("/dev/sda");
    print "partition table type: $parttype\n" if $debug;

    $g->part_init ("/dev/sdb", $parttype);
}

# In reality the number of sectors containing boot loader data will be
# less than this (although Windows 7 defaults to putting the first
# partition on sector 2048, and has quite a large boot loader).
#
# However make this large enough to be sure that we have copied over
# the boot loader.  We could also do this by looking for the sector
# offset of the first partition.
#
# It doesn't matter if we copy too much.
my $max_bootloader = 4096 * 512;

die __x("virt-resize: {file}: file is too small to be a disk image ({sz} bytes)\n",
        file => $infile, sz => $insize)
    if $insize < $max_bootloader;
die __x("virt-resize: {file}: file is too small to be a disk image ({sz} bytes)\n",
        file => $outfile, sz => $outsize)
    if $outsize < $max_bootloader;

# Copy the boot loader across.
do_copy_boot_loader () if $copy_boot_loader;

sub do_copy_boot_loader
{
    print "copying boot loader ...\n" if $debug;

    # Don't disturb the partition table that we just wrote.
    # https://secure.wikimedia.org/wikipedia/en/wiki/Master_Boot_Record
    # https://secure.wikimedia.org/wikipedia/en/wiki/GUID_Partition_Table

    my $bootsect = $g->pread_device ("/dev/sda", 446, 0);
    die __"virt-resize: short read" if length ($bootsect) < 446;

    $g->pwrite_device ("/dev/sdb", $bootsect, 0);

    my $start = 512;
    if ($parttype eq "gpt") {
        # XXX With 4K sectors does GPT just fit more entries in a
        # sector, or does it always use 34 sectors?
        $start = 17408;
    }

    my $loader = $g->pread_device ("/dev/sda", $max_bootloader, $start);
    die __"virt-resize: short read" if length ($loader) < $max_bootloader;

    $g->pwrite_device ("/dev/sdb", $loader, $start);
}

my $to_be_expanded = 0;

# Get the partitions on the source disk.
my @partitions;
my %partitions;
check_source_disk ();

sub check_source_disk
{
    local $_;

    # Partitions and PVs.
    my @p = $g->part_list ("/dev/sda");
    foreach (@p) {
        my $name = "/dev/sda" . $_->{part_num};
        push @partitions, $name;

        my %h = %$_;
        $h{name} = $name;
        $h{bootable} = $g->part_get_bootable ("/dev/sda", $h{part_num});
        eval { $h{mbr_id} = $g->part_get_mbr_id ("/dev/sda", $h{part_num}); };
        $partitions{$name} = \%h;
    }
}

# Examine each partition.
my @pvs_full = $g->pvs_full ();
examine_partition ($_) foreach @partitions;

sub examine_partition
{
    local $_;
    my $part = shift;

    # What is it?
    my $type = "unknown";
    eval {
        $type = $g->vfs_type ($part);
    };
    $partitions{$part}->{type} = $type;

    # Can we get the actual size of this object (ie. to find out if it
    # is smaller than the container for shrinking)?
    my $fssize;
    if ($type eq "LVM2_member") { # LVM PV
        foreach (@pvs_full) {
            $fssize = $_->{pv_size}
              if canonicalize ($_->{pv_name}) eq $part;
        }
    } else {                    # Something mountable?
        eval {
            $g->mount_ro ($part, "/");

            my %stat = $g->statvfs ("/");
            $fssize = $stat{bsize} * $stat{blocks};
        };

        eval {
            $g->umount_all ();
        };
    }

    # This might be undef if we didn't successfully find the size.  In
    # that case user won't be allowed to shrink this partition except
    # by forcing it.
    $partitions{$part}->{fssize} = $fssize;

    # Is it partition content that we know how to expand?
    $partitions{$part}->{can_expand_content} = 0;
    if ($expand_content) {
        if ($type eq "LVM2_member") {
            $partitions{$part}->{can_expand_content} = 1;
            $partitions{$part}->{expand_content_method} = "pvresize";
        } elsif ($type =~ /^ext[234]$/) {
            $partitions{$part}->{can_expand_content} = 1;
            $partitions{$part}->{expand_content_method} = "resize2fs";
        } elsif ($type eq "ntfs" && feature_available ($g, "ntfsprogs")) {
            $partitions{$part}->{can_expand_content} = 1;
            $partitions{$part}->{expand_content_method} = "ntfsresize";
        }
    }
}

if ($debug) {
    print "partitions found: ", join (", ", @partitions), "\n";
    foreach my $part (@partitions) {
        print "$part:\n";
        foreach (sort keys %{$partitions{$part}}) {
            print("\t", $_, " = ",
                  defined ($partitions{$part}->{$_})
                  ? $partitions{$part}->{$_} : "undef",
                  "\n");
        }
    }
}

# Examine the LVs (for --lv-expand option).
my @lvs = $g->lvs ();
my %lvs;
examine_lv ($_) foreach @lvs;
mark_lvs_to_expand ();

sub examine_lv
{
    local $_ = shift;

    $lvs{$_}->{name} = $_;

    my $type = "unknown";
    eval {
        $type = $g->vfs_type ($_);
    };
    $lvs{$_}->{type} = $type;

    if ($expand_content) {
        if ($type =~ /^ext[234]$/) {
            $lvs{$_}->{can_expand_content} = 1;
            $lvs{$_}->{expand_content_method} = "resize2fs";
        } elsif ($type eq "ntfs" && feature_available ($g, "ntfsprogs")) {
            $lvs{$_}->{can_expand_content} = 1;
            $lvs{$_}->{expand_content_method} = "ntfsresize";
        }
    }
}

sub mark_lvs_to_expand {
    local $_;

    foreach (@lv_expand) {
        die __x("virt-resize: no logical volume called {n}\n",
                n => $_)
            unless exists $lvs{$_};

        if ($lvs{$_}->{can_expand_content}) {
            $lvs{$_}->{will_expand_content} = 1;
            $to_be_expanded++;
        }
    }
}

sub find_partition
{
    local $_ = shift;
    my $option = shift;

    $_ = "/dev/$_" unless $_ =~ m{^/dev};
    $_ = canonicalize ($_);

    unless (exists $partitions{$_}) {
        die __x("{p}: partition not found in the source disk image, when using the '{opt}' command line option\n",
                p => $_,
                opt => $option)
    }

    if ($partitions{$_}->{ignore}) {
        die __x("{p}: partition ignored, you cannot use it in another command line argument\n",
                p => $_)
    }
    if ($partitions{$_}->{delete}) {
        die __x("{p}: partition deleted, you cannot use it in another command line argument\n",
                p => $_)
    }

    return $_;
}

# Handle --ignore.
do_ignore ($_) foreach @ignore;

sub do_ignore
{
    local $_ = shift;
    $_ = find_partition ($_, "--ignore");
    $partitions{$_}->{ignore} = 1;
}

# Handle --delete.
do_delete ($_) foreach @delete;

sub do_delete
{
    local $_ = shift;
    $_ = find_partition ($_, "--delete");
    $partitions{$_}->{delete} = 1;
}

# Handle --resize and --resize-force.
do_resize ($_, 0, "--resize") foreach @resize;
do_resize ($_, 1, "--resize-force") foreach @resize_force;

sub do_resize
{
    local $_ = shift;
    my $force = shift;
    my $option = shift;

    # Argument is "part=size" ...
    my ($part, $sizefield) = split /=/, $_, 2;
    $part = find_partition ($part, $option);

    if (exists $partitions{$part}->{newsize}) {
        die __x("{p}: this partition has already been marked for resizing\n",
                p => $part);
    }

    # Parse the size field.
    my $oldsize = $partitions{$part}->{part_size};
    my $newsize;
    if (!defined ($sizefield) || $sizefield eq "") {
        die __x("{p}: missing size field in {o} option\n",
                p => $part, o => $option);
    } elsif ($sizefield =~ /^([.\d]+)([bKMGTPE])$/) {
        $newsize = sizebytes ($1, $2);
    } elsif ($sizefield =~ /^\+([.\d]+)([bKMGTPE])$/) {
        my $incr = sizebytes ($1, $2);
        $newsize = $oldsize + $incr;
    } elsif ($sizefield =~ /^-([.\d]+)([bKMGTPE])$/) {
        my $decr = sizebytes ($1, $2);
        $newsize = $oldsize - $decr;
    } elsif ($sizefield =~ /^([.\d]+)%$/) {
        $newsize = $oldsize * $1 / 100;
    } elsif ($sizefield =~ /^\+([.\d]+)%$/) {
        $newsize = $oldsize + $oldsize * $1 / 100;
    } elsif ($sizefield =~ /^-([.\d]+)%$/) {
        $newsize = $oldsize - $oldsize * $1 / 100;
    } else {
        die __x("{p}: {f}: cannot parse size field\n",
                p => $part, f => $sizefield)
    }

    $newsize > 0 or
        die __x("{p}: new size is zero or negative\n", p => $part);

    mark_partition_for_resize ($part, $oldsize, $newsize, $force, $option);
}

sub mark_partition_for_resize
{
    local $_;
    my $part = shift;
    my $oldsize = shift;
    my $newsize = shift;
    my $force = shift;
    my $option = shift;

    # Do nothing if the size is the same.
    return if $oldsize == $newsize;

    my $bigger = $newsize > $oldsize;

    # Check there is space to shrink this.
    unless ($bigger || $force) {
        if (! $partitions{$part}->{fssize} ||
            $partitions{$part}->{fssize} > $newsize) {
            die __x("{p}: cannot make this partition smaller because it contains a\nfilesystem, physical volume or other content that is larger than the new size.\nYou have to resize the content first, see virt-resize(1).\n",
                    p => $part);
        }
    }

    $partitions{$part}->{newsize} = $newsize;

    if ($partitions{$part}->{can_expand_content} && $bigger) {
        $partitions{$part}->{will_expand_content} = 1;
        $to_be_expanded++;
    }
}

# Handle --expand and --shrink.
my $surplus;
if (defined $expand && defined $shrink) {
    die __"virt-resize: you cannot use options --expand and --shrink together\n"
}
if (defined $expand || defined $shrink) {
    calculate_surplus ();

    if ($debug) {
        print "surplus before --expand or --shrink: $surplus (",
          human_size ($surplus), ")\n";
    }

    do_expand () if $expand;
    do_shrink () if $shrink;
}

# (Re-)calculate surplus after doing expand or shrink.
calculate_surplus ();

# Add up the total space required on the target so far, compared
# to the size of the target.  We end up with a surplus or deficit.
sub calculate_surplus
{
    local $_;

    # We need some overhead for partitioning.  Worst case would be for
    # EFI partitioning + massive per-partition alignment.
    my $overhead = $sectsize * (
        2 * 64 +                   # GPT start and end
        (64 * (@partitions + 1))   # Maximum alignment
        ) +
        ($max_bootloader - 64 * 512); # boot loader

    my $required = 0;
    foreach (@partitions) {
        if ($partitions{$_}->{newsize}) {
            $required += $partitions{$_}->{newsize}
        } else {
            $required += $partitions{$_}->{part_size}
        }
    }

    # Compare that to the actual target disk.
    $surplus = $outsize - ($required + $overhead);
}

sub do_expand
{
    local $_;

    unless ($surplus > 0) {
        die __x("virt-resize: error: cannot use --expand when there is no surplus space to\nexpand into.  You need to make the target disk larger by at least {h}.\n",
                h => human_size (-$surplus));
    }

    my $part = find_partition ($expand, "--expand");
    my $oldsize = $partitions{$part}->{part_size};
    mark_partition_for_resize ($part, $oldsize, $oldsize + $surplus,
                               0, "--expand");
}

sub do_shrink
{
    local $_;

    unless ($surplus < 0) {
        die __"virt-resize: error: cannot use --shrink because there is no deficit\n(see 'deficit' in the virt-resize(1) man page)\n"
    }

    my $part = find_partition ($shrink, "--shrink");
    my $oldsize = $partitions{$part}->{part_size};
    mark_partition_for_resize ($part, $oldsize, $oldsize + $surplus,
                               0, "--shrink");
}

# Print summary.
print_summary () unless $quiet;

sub print_summary
{
    local $_;
    print __"Summary of changes:\n";

    foreach my $part (@partitions) {
        if ($partitions{$part}->{ignore}) {
            print __x("{p}: partition will be ignored\n", p => $part);
        } elsif ($partitions{$part}->{delete}) {
            print __x("{p}: partition will be deleted\n", p => $part);
        } elsif ($partitions{$part}->{newsize}) {
            print __x("{p}: partition will be resized from {oldsize} to {newsize}\n",
                      p => $part,
                      oldsize => human_size ($partitions{$part}->{part_size}),
                      newsize => human_size ($partitions{$part}->{newsize}));
            if ($partitions{$part}->{will_expand_content}) {
                print __x("{p}: content will be expanded using the '{meth}' method\n",
                          p => $part,
                          meth => $partitions{$part}->{expand_content_method});
            }
        } else {
            print __x("{p}: partition will be left alone\n", p => $part);
        }
    }

    foreach my $lv (@lv_expand) {
        print __x("{n}: LV will be expanded to maximum size\n",
                  n => $lv);
    }

    foreach my $lv (@lvs) {
        if ($lvs{$lv}->{will_expand_content}) {
            print __x("{n}: content will be expanded using the '{meth}' method\n",
                      n => $lv,
                      meth => $lvs{$lv}->{expand_content_method});
        }
    }

    if ($surplus > 0) {
        print __x("There is a surplus of {spl} bytes ({h}).\n",
                  spl => $surplus,
                  h => human_size ($surplus));
        if ($extra_partition) {
            if ($surplus >= $min_extra_partition) {
                print __"An extra partition will be created for the surplus.\n";
            } else {
                print __"The surplus space is not large enough for an extra partition to be created\nand so it will just be ignored.\n";
            }
        } else {
            print __"The surplus space will be ignored.  Run a partitioning program in the guest\nto partition this extra space if you want.\n";
        }
    } elsif ($surplus < 0) {
        die __x("virt-resize: error: there is a deficit of {def} bytes ({h}).\nYou need to make the target disk larger by at least this amount,\nor adjust your resizing requests.\n",
                def => -$surplus,
                h => human_size (-$surplus));
    }
}

exit 0 if $dryrun;

# Repartition the target disk.
my $nextpart = 1;
repartition ();

sub repartition
{
    local $_;

    # Work out where to start the first partition.
    die __"virt-resize: source disk does not have a first partition\n"
        unless exists ($partitions{"/dev/sda1"});
    my $start = $partitions{"/dev/sda1"}->{part_start} / $sectsize;

    # Align to 64.
    $start = ($start + 63) & ~63;

    print "starting to partition from $start\n" if $debug;

    # Create the new partitions.
    foreach my $part (@partitions) {
        unless ($partitions{$part}->{delete}) {
            # Size in sectors.
            my $size;
            if ($partitions{$part}->{newsize}) {
                $size = ($partitions{$part}->{newsize} + $sectsize - 1)
                    / $sectsize;
            } else {
                $size = ($partitions{$part}->{part_size} + $sectsize - 1)
                    / $sectsize;
            }

            # Create it.
            my ($target, $end, $part_num) = add_partition ($start, $size);
            $partitions{$part}->{target} = $target;

            if ($partitions{$part}->{bootable}) {
                $g->part_set_bootable ("/dev/sdb", $part_num, 1);
            }

            if ($partitions{$part}->{mbr_id}) {
                $g->part_set_mbr_id ("/dev/sdb", $part_num,
                                     $partitions{$part}->{mbr_id});
            }

            # Start of next partition + alignment.
            $start = $end + 1;
            $start = ($start + 63) & ~63;
        }
    }

    # Create surplus partition.
    if ($extra_partition && $surplus >= $min_extra_partition) {
        add_partition ($start, $outsize / $sectsize - 64 - $start);
    }
}

# Add a partition.
sub add_partition
{
    local $_;
    my $start = shift;
    my $size = shift;

    my ($target, $end, $part_num);

    if ($nextpart <= 3 || $parttype ne "msdos") {
        $target = "/dev/sdb$nextpart";
        $end = $start + $size - 1;
        $g->part_add ("/dev/sdb", "primary", $start, $end);
        $part_num = $nextpart++;
    } else {
        if ($nextpart == 4) {
            $g->part_add ("/dev/sdb", "extended", $start, -1);
            $part_num = $nextpart++;
            $start += 64;
        }
        $target = "/dev/sdb$nextpart";
        $end = $start + $size - 1;
        $g->part_add ("/dev/sdb", "logical", $start, $end);
        $part_num = $nextpart++;
    }

    return ($target, $end, $part_num);
}

# Copy over the data.
copy_data ();

sub copy_data
{
    foreach my $part (@partitions)
    {
        unless ($partitions{$part}->{ignore}) {
            my $target = $partitions{$part}->{target};
            if ($target) {
                my $oldsize = $partitions{$part}->{part_size};
                my $newsize;
                if ($partitions{$part}->{newsize}) {
                    $newsize = $partitions{$part}->{newsize};
                } else {
                    $newsize = $partitions{$part}->{part_size};
                }

                if (!$quiet && !$debug) {
                    print __x("Copying {p} ...\n", p => $part);
                }

                $g->copy_size ($part, $target,
                               $newsize < $oldsize ? $newsize : $oldsize);
            }
        }
    }
}

# After copying the data over we must shut down and restart the
# appliance in order to expand the content.  The reason for this may
# not be obvious, but it's because otherwise we'll have duplicate VGs
# (the old VG(s) and the new VG(s)) which breaks LVM.
#
# The restart is only required if we're going to expand something.

if ($to_be_expanded > 0) {
    restart_appliance ();
    expand_partitions ();
    expand_lvs ();
    expand_lvs_content ();
}

sub restart_appliance
{
    # Sync disk and exit.
    $g->umount_all ();
    $g->sync ();
    undef $g;

    $g = Sys::Guestfs->new ();
    $g->set_trace (1) if $debug;
    my @args = ($outfile);
    push @args, format => $output_format if defined $output_format;
    $g->add_drive_opts (@args);
    $g->launch ();

    # Target partitions have changed from /dev/sdb to /dev/sda,
    # so change them.
    foreach my $part (@partitions)
    {
        my $target = $partitions{$part}->{target};
        if ($target) {
            if ($target =~ m{/dev/(.)db(.*)}) {
                $partitions{$part}->{target} = "/dev/$1da$2";
            } else {
                die "internal error: unexpected partition target: $target";
            }
        }
    }
}

sub expand_partitions
{
    foreach my $part (@partitions)
    {
        unless ($partitions{$part}->{ignore}) {
            my $target = $partitions{$part}->{target};
            if ($target) {
                # Expand if requested.
                if ($partitions{$part}->{will_expand_content}) {
                    if (!$quiet && !$debug) {
                        print __x("Expanding {p} using the '{meth}' method\n",
                                  p => $part,
                                  meth => $partitions{$part}->{expand_content_method});
                    }
                    expand_target_partition ($part)
                }
            }
        }
    }
}

sub expand_target_partition
{
    local $_;
    my $part = shift;

    # Assertions.
    die unless $part;
    die unless $partitions{$part}->{can_expand_content};
    die unless $partitions{$part}->{will_expand_content};
    die unless $partitions{$part}->{expand_content_method};
    die unless $partitions{$part}->{target};
    die unless $expand_content;

    my $target = $partitions{$part}->{target};
    my $method = $partitions{$part}->{expand_content_method};
    if ($method eq "pvresize") {
        $g->pvresize ($target);
    }
    elsif ($method eq "resize2fs") {
        $g->e2fsck_f ($target);
        $g->resize2fs ($target);
    }
    elsif ($method eq "ntfsresize") {
        $g->ntfsresize ($target);
    }
    else {
        die "internal error: unknown method: $method";
    }
}

sub expand_lvs
{
    local $_;

    foreach (@lv_expand) {
        $g->lvresize_free ($_, 100);
    }
}

sub expand_lvs_content
{
    local $_;

    foreach (@lvs) {
        if ($lvs{$_}->{will_expand_content}) {
            my $method = $lvs{$_}->{expand_content_method};
            if (!$quiet && !$debug) {
                print __x("Expanding {p} using the '{meth}' method\n",
                          p => $_, meth => $method);
                    }
            if ($method eq "resize2fs") {
                $g->e2fsck_f ($_);
                $g->resize2fs ($_);
            } elsif ($method eq "ntfsresize") {
                $g->ntfsresize ($_);
            } else {
                die "internal error: unknown method: $method";
            }
        }
    }
}

# Sync disk and exit.
$g->umount_all ();
$g->sync ();
undef $g;

exit 0;

sub sizebytes
{
    local $_ = shift;
    my $unit = shift;

    $_ *= 1024 if $unit =~ /[KMGTPE]/;
    $_ *= 1024 if $unit =~ /[MGTPE]/;
    $_ *= 1024 if $unit =~ /[GTPE]/;
    $_ *= 1024 if $unit =~ /[TPE]/;
    $_ *= 1024 if $unit =~ /[PE]/;
    $_ *= 1024 if $unit =~ /[E]/;

    return floor($_);
}

# Convert a number of bytes to a human-readable number.
sub human_size
{
    local $_ = shift;

    my $sgn = "";
    if ($_ < 0) {
        $sgn = "-";
        $_ = -$_;
    }

    $_ /= 1024;

    if ($_ < 1024) {
        sprintf "%s%dK", $sgn, $_;
    } elsif ($_ < 1024 * 1024) {
        sprintf "%s%.1fM", $sgn, ($_ / 1024);
    } else {
        sprintf "%s%.1fG", $sgn, ($_ / 1024 / 1024);
    }
}

# The reverse of device name translation, see
# BLOCK DEVICE NAMING in guestfs(3).
sub canonicalize
{
    local $_ = shift;

    if (m{^/dev/[hv]d([a-z]\d*)$}) {
        return "/dev/sd$1";
    }
    $_;
}

# Not as sophisticated as the guestfish progress bar, because
# I intend to use an external library for this at some point (XXX).
sub progress_callback
{
    my $proc_nr = shift;
    my $serial = shift;
    my $position = shift;
    my $total = shift;

    my $ratio = $position / $total;
    if ($ratio < 0) { $ratio = 0 }
    elsif ($ratio > 1) { $ratio = 1 }

    my $dots = int ($ratio * 76);

    print "[", "#"x$dots, "-"x(76-$dots), "]\r";
    print "\n" if $ratio == 1;
}

=head1 NOTES

=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.

=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.

Windows may initiate a lengthy "chkdsk" on first boot after a resize,
if NTFS partitions have been expanded.  This is just a safety check
and (unless it find errors) is nothing to worry about.

=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.

 guestfish -i -a newdisk
 ><fs> cat /boot/grub/device.map
 # check the contents of this file are sensible or
 # edit the file if necessary
 ><fs> grub-install / /dev/vda
 ><fs> exit

For more flexible guest reconfiguration, including if you need to
specify other parameters to grub-install, use L<virt-rescue(1)>.

=head1 ALTERNATIVE TOOLS

There are several proprietary tools for resizing partitions.  We
won't mention any here.

L<parted(8)> and its graphical shell gparted can do some types of
resizing operations on disk images.  They can resize and move
partitions, but I don't think they can do anything with the contents,
and they certainly don't understand LVM.

L<guestfish(1)> can do everything that virt-resize can do and a lot
more, but at a much lower level.  You will probably end up
hand-calculating sector offsets, which is something that virt-resize
was designed to avoid.  If you want to see the guestfish-equivalent
commands that virt-resize runs, use the C<--debug> flag.

=head1 SHELL QUOTING

Libvirt guest names can contain arbitrary characters, some of which
have meaning to the shell such as C<#> and space.  You may need to
quote or escape these characters on the command line.  See the shell
manual page L<sh(1)> for details.

=head1 SEE ALSO

L<virt-filesystems(1)>,
L<virt-df(1)>,
L<guestfs(3)>,
L<guestfish(1)>,
L<lvm(8)>,
L<pvresize(8)>,
L<lvresize(8)>,
L<resize2fs(8)>,
L<ntfsresize(8)>,
L<virsh(1)>,
L<parted(8)>,
L<truncate(1)>,
L<fallocate(1)>,
L<grub(8)>,
L<grub-install(8)>,
L<virt-rescue(1)>,
L<Sys::Guestfs(3)>,
L<http://libguestfs.org/>.

=head1 AUTHOR

Richard W.M. Jones L<http://people.redhat.com/~rjones/>

=head1 COPYRIGHT

Copyright (C) 2010 Red Hat Inc.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.