pve-6.1-3-diff-backup-addon

#!/bin/bash

set -eo pipefail

echo "Proxmox VE 6.1-3 - differential backup support, v3"
echo "Kamil Trzcinski, http://ayufan.eu/, ayufan@ayufan.eu"
echo ""

patch_diff() {
  grep -A 10000 "^__PATCH__$" "$0"
}

patch_revert() {
  patch_diff | patch --reverse --quiet -p1 --batch --ignore-whitespace -d "$@"
}

patch_apply() {
  patch_diff | patch --forward -p1 --batch --ignore-whitespace -d "$@"
}

print_and_run() {
  echo "$ $@"
  "$@"
}

patch_test() {
  local TYPE="$1"
  local VMID="$2"
  local EXT="$3"
  local TARGET_VMID="$4"
  shift 4

  echo "Testing type=$TYPE vmid=$VMID:$TARGET_VMID ext=$ext flags=$@..."

  print_and_run rm -rf /var/lib/vz/dump/vzdump-$TYPE-$VMID-*

  case $TYPE in
    qemu)
      print_and_run qm status "$VMID"

      print_and_run vzdump --fullbackup=0 "$@" $VMID
      print_and_run vzdump --fullbackup=5 "$@" $VMID

      print_and_run qmrestore --force=true /var/lib/vz/dump/vzdump-qemu-$VMID-*.$EXT $TARGET_VMID
      print_and_run qmrestore --force=true /var/lib/vz/dump/vzdump-qemu-$VMID-*.$EXT-*.vcdiff $TARGET_VMID
      ;;

    lxc)
      print_and_run pct status "$VMID"

      print_and_run vzdump --fullbackup=0 "$@" $VMID
      print_and_run vzdump --fullbackup=5 "$@" $VMID

      print_and_run pct restore $TARGET_VMID /var/lib/vz/dump/vzdump-lxc-$VMID-*.$EXT --force=true
      print_and_run pct restore $TARGET_VMID /var/lib/vz/dump/vzdump-lxc-$VMID-*.$EXT-*.vcdiff --force=true
      ;;
  esac
}

case $1 in
revert)
  if patch_revert / --dry-run
  then
    patch_revert /
    echo "RESTORED"
  else
    echo "FAILED to restore!"
    exit 1
  fi

  echo ""
  print_and_run service pveproxy restart
  print_and_run service pvedaemon restart
  ;;

apply)
  if patch_apply / --dry-run
  then
    print_and_run patch_apply /
    echo "APPLIED"
  else
    echo "FAILED to apply!"
    exit 1
  fi

  echo ""
  print_and_run service pveproxy restart
  print_and_run service pvedaemon restart
  ;;

reinstall)
  PATHS=$(patch_diff | grep "^+++ b/" | sed 's/^\+\+\+ b//g')
  echo "Affected file paths:"
  echo "$PATHS"
  echo ""

  PACKAGES=$(dpkg --search $PATHS | cut -d: -f1 | tr -d , | sort -u)
  echo "Affected packages:"
  echo "$PACKAGES"
  echo ""

  echo "Press Enter to continue, or Ctrl-C to cancel."
  read PROMPT

  apt-get --reinstall install $PACKAGES
  ;;

test)
  print_and_run patch_apply / --dry-run --batch
  ;;

patch)
  patch_diff
  ;;

selftest-qemu)
  echo "This is destructive command that requires:"
  echo ""
  echo "- the VM500 present"
  echo "- and VM510 empty"
  echo ""

  if ! qm status 500 &> /dev/null; then
    echo "The VM500 has to be present!"
    exit 1
  fi

  echo "Press enter to continue, Ctrl-C to abort"
  read LINE

  patch_test qemu 500 vma 510
  patch_test qemu 500 vma.lzo 510 --compress=lzo
  ;;

selftest-lxc)
  echo "This is destructive command that requires:"
  echo ""
  echo "- the CT501 present"
  echo "- and CT511 empty"
  echo ""

  if ! pct status 501 &> /dev/null; then
    echo "The CT501 has to be present!"
    exit 1
  fi

  echo "Press enter to continue, Ctrl-C to abort"
  read LINE

  patch_test lxc 501 tar 511
  patch_test lxc 501 tar.lzo 511 --compress=lzo
  ;;

*)
  echo "usage: $0 [apply|revert|test|patch]"
  exit 1
  ;;
esac

exit 0

__PATCH__
diff --git a/usr/share/pve-manager/js/pvemanagerlib.js b/usr/share/pve-manager/js/pvemanagerlib.js
index 7a92574..d2bca5b 100644
--- a/usr/share/pve-manager/js/pvemanagerlib.js
+++ b/usr/share/pve-manager/js/pvemanagerlib.js
@@ -38372,6 +42309,25 @@ Ext.define('PVE.dc.BackupEdit', {
        name: 'mode'
        },
        {
+       xtype: 'numberfield',
+       fieldLabel: gettext('Max Backups'),
+       name: 'maxfiles',
+       minValue: 0,
+       maxValue: 365,
+       value: me.create ? '1' : undefined,
+       allowBlank: false
+       },
+       {
+       xtype: 'numberfield',
+       fieldLabel: gettext('Full Backup Every'),
+       name: 'fullbackup',
+       emptyText : gettext('Days'),
+       minValue: 0,
+       maxValue: 60,
+       value: me.create ? '0' : undefined,
+       allowBlank: true
+       },
+       {
        xtype: 'proxmoxcheckbox',
        fieldLabel: gettext('Enable'),
        name: 'enabled',
diff --git a/usr/share/perl5/PVE/LXC/Create.pm b/usr/share/perl5/PVE/LXC/Create.pm
index cf73dba..e860444 100644
--- a/usr/share/perl5/PVE/LXC/Create.pm
+++ b/usr/share/perl5/PVE/LXC/Create.pm
@@ -71,7 +71,10 @@ sub restore_archive {
     my $archive_fh;
     my $tar_input = '<&STDIN';
     my @compression_opt;
-    if ($archive ne '-') {
+
+    if (PVE::Storage::get_full_backup($archive)) {
+        # ignore
+    } elsif ($archive ne '-') {
        # GNU tar refuses to autodetect this... *sigh*
        my %compression_map = (
            '.gz'  => '-z',
@@ -106,8 +109,19 @@ sub restore_archive {
     push @$cmd, '--anchored';
     push @$cmd, '--exclude' , './dev/*';
 
+    $cmd = [ $cmd ];
+
+    if (my $fullbackup = PVE::Storage::get_full_backup($archive)) {
+        print "extracting from differential archive, using full backup '$fullbackup'\n";
+
+        $cmd = [
+           [ "pve-xdelta3", "-q", "-d", "-c", "-R", "-s", $fullbackup, $archive ],
+           [ @$userns_cmd, 'tar', 'xpf', '-', '--numeric-owner', '--totals', @PVE::Storage::Plugin::COMMON_TAR_FLAGS, '-C', $rootdir, '--skip-old-files', '--anchored', '--exclude' , './dev/*']
+        ];
+    }
+
     if (defined($bwlimit)) {
-       $cmd = [ ['cstream', '-t', $bwlimit*1024], $cmd ];
+       splice @$cmd, 1, 0, ['cstream', '-t', $bwlimit*1024];
     }
 
     if ($archive eq '-') {
diff --git a/usr/share/perl5/PVE/QemuServer.pm b/usr/share/perl5/PVE/QemuServer.pm
index 7becdeb..516d5a5 100644
--- a/usr/share/perl5/PVE/QemuServer.pm
+++ b/usr/share/perl5/PVE/QemuServer.pm
@@ -5944,8 +5944,18 @@ sub tar_archive_read_firstfile {
 
     die "ERROR: file '$archive' does not exist\n" if ! -f $archive;
 
+    my $cmd = undef;
+
+    if ($archive =~ m!([^/]*vzdump-([a-z]*)-(\d*)-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.(tgz|(tar(\.(gz|lzo))?)))--differential-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.vcdiff(\.(gz|lzo))?$!) {
+   my $fullbackup = $archive;
+   $fullbackup =~ s!([^/]*vzdump-([a-z]+)-(\d+)-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.(tgz|(tar(\.(gz|lzo))?)))--differential-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.vcdiff(\.(gz|lzo))?!$1!;
+   $cmd = "-|pve-xdelta3 -q -d -c -R -s '$fullbackup' '$archive' |tar t|";
+    } else {
+   $cmd = "-|tar tf '$archive'|";
+    }
+
     # try to detect archive type first
-    my $pid = open (my $fh, '-|', 'tar', 'tf', $archive) ||
+    my $pid = open (my $fh, $cmd) ||
 	die "unable to open file '$archive'\n";
     my $firstfile = <$fh>;
     kill 15, $pid;
@@ -6297,7 +6307,13 @@ sub restore_vma_archive {
 	}
     }
 
-    if ($comp) {
+    if ($archive =~ m!([^/]*vzdump-([a-z]*)-(\d*)-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.(vma(\.(gz|lzo))?))--differential-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.vcdiff(\.(gz|lzo))?$!) {
+        my $fullbackup = $archive;
+        $fullbackup =~ s!([^/]*vzdump-([a-z]+)-(\d+)-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.(vma(\.(gz|lzo))?))--differential-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.vcdiff(\.(gz|lzo))?!$1!;
+        print "extracting from differential archive, using full backup '$fullbackup'\n";
+        my $uncomp = ['pve-xdelta3', '-q', '-d', '-c', '-R', '-s', $fullbackup, $readfrom];
+	$add_pipe->($uncomp);
+    } elsif ($comp) {
 	my $cmd;
 	if ($comp eq 'gzip') {
 	    $cmd = ['zcat', $readfrom];
@@ -6617,8 +6718,17 @@ sub restore_tar_archive {
 
     # tar option "xf" does not autodetect compression when read from STDIN,
     # so we pipe to zcat
-    my $cmd = "zcat -f|tar xf " . PVE::Tools::shellquote($archive) . " " .
-   PVE::Tools::shellquote("--to-command=$tocmd");
+    my $cmd = undef;
+
+    if ($archive =~ m!([^/]*vzdump-([a-z]*)-(\d*)-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.(tgz|(tar(\.(gz|lzo))?)))--differential-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.vcdiff(\.(gz|lzo))?$!) {
+   my $fullbackup = $archive;
+   $fullbackup =~ s!([^/]*vzdump-([a-z]+)-(\d+)-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.(tgz|(tar(\.(gz|lzo))?)))--differential-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.vcdiff(\.(gz|lzo))?!$1!;
+   print "extracting from differential archive, using full backup '$fullbackup'\n";
+   $cmd = "pve-xdelta3 -q -d -c -R -s '$fullbackup' '$archive' |tar x " . PVE::Tools::shellquote("--to-command=$tocmd");
+    } else {
+   $cmd = "zcat -f|tar xf " . PVE::Tools::shellquote($archive) . " " .
+       PVE::Tools::shellquote("--to-command=$tocmd");
+    }
 
     my $tmpdir = "/var/tmp/vzdumptmp$$";
     mkpath $tmpdir;
diff --git a/usr/share/perl5/PVE/Storage.pm b/usr/share/perl5/PVE/Storage.pm
index 53bdd24..72e10bb 100644
--- a/usr/share/perl5/PVE/Storage.pm
+++ b/usr/share/perl5/PVE/Storage.pm
@@ -512,7 +494,7 @@ sub path_to_volume_id {
 	} elsif ($path =~ m!^$privatedir/(\d+)$!) {
 	    my $vmid = $1;
 	    return ('rootdir', "$sid:rootdir/$vmid");
-   } elsif ($path =~ m!^$backupdir/([^/]+\.(tar|tar\.gz|tar\.lzo|tgz|vma|vma\.gz|vma\.lzo))$!) {
+   } elsif ($path =~ m!^$backupdir/([^/]+\.(tar|tar\.gz|tar\.lzo|tgz|vma|vma\.gz|vma\.lzo|vcdiff|vcdiff\.gz|vcdiff\.lzo))$!) {
 	    my $name = $1;
 	    return ('iso', "$sid:backup/$name");
 	}
@@ -1263,13 +1334,30 @@ sub foreach_volid {
     }
 }
 
+sub get_full_backup {
+   my ($archive) = @_;
+   if ($archive =~ m!([^/]*vzdump-([a-z]*)-(\d*)-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.(tgz|(tar(\.(gz|lzo))?)))--differential-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.vcdiff(\.(gz|lzo))?$!) {
+       my $fullbackup = $archive;
+       $fullbackup =~ s!([^/]*vzdump-([a-z]+)-(\d+)-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.(tgz|(tar(\.(gz|lzo))?)))--differential-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.vcdiff(\.(gz|lzo))?!$1!;
+       return $fullbackup;
+   }
+   return undef;
+}
+
 sub extract_vzdump_config_tar {
     my ($archive, $conf_re) = @_;
 
     die "ERROR: file '$archive' does not exist\n" if ! -f $archive;
 
-    my $pid = open(my $fh, '-|', 'tar', 'tf', $archive) ||
-       die "unable to open file '$archive'\n";
+   my $pid;
+   my $fh;
+
+   if (my $fullbackup = get_full_backup($archive)) {
+       $pid = open($fh, '-|', 'bash', '-c' , "pve-xdelta3 -q -d -c -R -s '$fullbackup' '$archive' | tar tf -")
+           || die "unable to open file '$archive'\n";
+   } else {
+       $pid = open($fh, '-|', 'tar', 'tf', $archive) || die "unable to open file '$archive'\n";
+   }
 
     my $file;
     while (defined($file = <$fh>)) {
@@ -1292,7 +1380,15 @@ sub extract_vzdump_config_tar {
 	$raw .= "$output\n";
     };
 
-    PVE::Tools::run_command(['tar', '-xpOf', $archive, $file, '--occurrence'], outfunc => $out);
+    my $cmd = ['tar', '-xpOf', $archive, $file, '--occurrence'];
+   if (my $fullbackup = get_full_backup($archive)) {
+       $cmd = [
+           [ "bash", "-c", "pve-xdelta3 -q -d -c -R -s '$fullbackup' '$archive' || true" ],
+           [ 'tar', '-xpOf', '-', $file, '--occurrence' ]
+       ];
+   }
+
+    PVE::Tools::run_command($cmd, outfunc => $out);
 
     return wantarray ? ($raw, $file) : $raw;
 }
diff --git a/usr/share/perl5/PVE/Storage/Plugin.pm b/usr/share/perl5/PVE/Storage/Plugin.pm
index 163871d..da6ce2d 100644
--- a/usr/share/perl5/PVE/Storage/Plugin.pm
+++ b/usr/share/perl5/PVE/Storage/Plugin.pm
@@ -423,7 +398,7 @@ sub parse_volname {
 	return ('vztmpl', $1);
     } elsif ($volname =~ m!^rootdir/(\d+)$!) {
 	return ('rootdir', $1, $1);
-    } elsif ($volname =~ m!^backup/([^/]+(\.(tar|tar\.gz|tar\.lzo|tgz|vma|vma\.gz|vma\.lzo)))$!) {
+    } elsif ($volname =~ m!^backup/([^/]+(\.(tar|tar\.gz|tar\.lzo|tgz|vma|vma\.gz|vma\.lzo|vcdiff|vcdiff\.gz|vcdiff\.lzo)))$!) {
 	my $fn = $1;
 	if ($fn =~ m/^vzdump-(openvz|lxc|qemu)-(\d+)-.+/) {
 	    return ('backup', $fn, $2);
@@ -913,7 +925,7 @@ my $get_subdir_files = sub {
 
        } elsif ($tt eq 'backup') {
            next if defined($vmid) && $fn !~  m/\S+-$vmid-\S+/;
-           next if $fn !~ m!/([^/]+\.(tar|tar\.gz|tar\.lzo|tgz|vma|vma\.gz|vma\.lzo))$!;
+           next if $fn !~ m!/([^/]+\.(tar|tar\.gz|tar\.lzo|tgz|vma|vma\.gz|vma\.lzo|vcdiff|vcdiff\.gz|vcdiff\.lzo))$!;
 
            $info = { volid => "$sid:backup/$1", format => $2 };
 
diff --git a/usr/share/perl5/PVE/VZDump.pm b/usr/share/perl5/PVE/VZDump.pm
index 510d964..d950ee2 100644
--- a/usr/share/perl5/PVE/VZDump/Common.pm
+++ b/usr/share/perl5/PVE/VZDump/Common.pm
@@ -203,6 +203,13 @@ my $confdesc = {
 	minimum => 1,
 	default => 1,
     },
+    fullbackup => {
+    type => 'integer',
+    description => "Maximal days of validity for full backups to be used for creating differentials.",
+    optional => 1,
+    minimum => 0,
+    default => 0,
+    },
     remove => {
 	type => 'boolean',
 	description => "Remove old backup files if there are more than 'maxfiles' backup files.",
diff --git a/usr/share/perl5/PVE/VZDump.pm b/usr/share/perl5/PVE/VZDump.pm
index 510d964..d950ee2 100644
--- a/usr/share/perl5/PVE/VZDump.pm
+++ b/usr/share/perl5/PVE/VZDump.pm
@@ -8,6 +10,7 @@ use IO::File;
 use IO::Select;
 use IPC::Open3;
 use File::Path;
+use File::Basename;
 use PVE::RPCEnvironment;
 use PVE::Storage;
 use PVE::Cluster qw(cfs_read_file);
@@ -584,6 +585,22 @@ sub get_backup_file_list {
 
     return $bklist;
 }
+
+sub get_differential_backup_file_list {
+    my ($dir, $bkname, $exclude_fn) = @_;
+
+    my $bklist = [];
+    foreach my $fn (<$dir/${bkname}-*>) {
+   next if $exclude_fn && $fn eq $exclude_fn;
+   if ($fn =~ m!/(${bkname}--differential-(\d{4})_(\d{2})_(\d{2})-(\d{2})_(\d{2})_(\d{2})\.vcdiff(\.(gz|lzo))?)$!) {
+       $fn = "$dir/$1"; # untaint
+       my $t = timelocal ($7, $6, $5, $4, $3 - 1, $2 - 1900);
+       push @$bklist, [$fn, $t];
+   }
+    }
+
+    return $bklist;
+}
  
 sub exec_backup_task {
     my ($self, $task) = @_;
@@ -635,13 +803,40 @@ sub exec_backup_task {
 		if scalar(@$bklist) >= $maxfiles;
 	}
 
-	my $logfile = $task->{logfile} = "$opts->{dumpdir}/$basename.log";
+    my $ext = $vmtype eq 'qemu' ? '.vma' : '.tar';
+    my ($comp, $comp_ext) = compressor_info($opts);
+    if ($comp && $comp_ext) {
+        $ext .= ".${comp_ext}";
+    }
 
-	my $ext = $vmtype eq 'qemu' ? '.vma' : '.tar';
-	my ($comp, $comp_ext) = compressor_info($opts);
-	if ($comp && $comp_ext) {
-	    $ext .= ".${comp_ext}";
-	}
+    my $fullbackup = undef;
+    if ($opts->{fullbackup} && !$opts->{stdout}) {
+        my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime();
+        my $bklist = get_backup_file_list($opts->{dumpdir}, $bkname);
+        $bklist = [ sort { $b->[1] <=> $a->[1] } @$bklist ];
+        my $mintime = timelocal($sec, $min, $hour, $mday, $mon, $year) -
+        	$opts->{fullbackup} * 24 * 60 * 60 -
+        	12 * 60 * 60; # - 12h just to make sure that on last day we create full backup
+
+        foreach my $d (@$bklist) {
+        next if $mintime > $d->[1];
+
+        $fullbackup = $d->[0];
+        $basename = basename($fullbackup);
+        $basename = sprintf "${basename}--differential-%04d_%02d_%02d-%02d_%02d_%02d",
+            $year + 1900, $mon + 1, $mday,
+            $hour, $min, $sec;
+        $ext = ".vcdiff";
+
+        debugmsg ('info', "doing differential backup against '$fullbackup'");
+        last;
+        }
+
+        debugmsg ('info', "doing full backup, because no backup found in last $opts->{fullbackup} day(s)")
+        if !$fullbackup;
+    }
+
+   my $logfile = $task->{logfile} = "$opts->{dumpdir}/$basename.log";
 
 	if ($opts->{stdout}) {
 	    $task->{tarfile} = '-';
@@ -814,7 +1016,7 @@ sub exec_backup_task {
 	}
 
 	debugmsg ('info', "creating archive '$task->{tarfile}'", $logfd);
-   $plugin->archive($task, $vmid, $task->{tmptar}, $comp);
+   $plugin->archive($task, $vmid, $task->{tmptar}, $comp, $fullbackup);
 
 	rename ($task->{tmptar}, $task->{tarfile}) ||
 	    die "unable to rename '$task->{tmptar}' to '$task->{tarfile}'\n";
@@ -826,7 +1028,7 @@ sub exec_backup_task {
 
 	# purge older backup
 
-   if ($maxfiles && $opts->{remove}) {
+   if ($maxfiles && $opts->{remove} && !$fullbackup) {
 	    my $bklist = get_backup_file_list($opts->{dumpdir}, $bkname, $task->{tarfile});
 	    $bklist = [ sort { $b->[1] <=> $a->[1] } @$bklist ];
 
@@ -837,6 +1039,16 @@ sub exec_backup_task {
 		my $logfn = $d->[0];
 		$logfn =~ s/\.(tgz|((tar|vma)(\.(gz|lzo))?))$/\.log/;
 		unlink $logfn;
+
+       my $dbklist = get_differential_backup_file_list($opts->{dumpdir}, basename($d->[0]));
+
+       foreach my $df (@$dbklist) {
+           debugmsg ('info', "delete old differential backup '$df->[0]'", $logfd);
+           unlink $df->[0];
+           $logfn = $df->[0];
+           $logfn =~ s/\.(vcdiff(\.(gz|lzo))?)$/\.log/;
+           unlink $logfn;
+       }
 	    }
 	}
 
diff --git a/usr/share/perl5/PVE/VZDump/LXC.pm b/usr/share/perl5/PVE/VZDump/LXC.pm
index ae793dc..06a88e7 100644
--- a/usr/share/perl5/PVE/VZDump/LXC.pm
+++ b/usr/share/perl5/PVE/VZDump/LXC.pm
@@ -303,7 +296,7 @@ sub assemble {
 }
 
 sub archive {
-    my ($self, $task, $vmid, $filename, $comp) = @_;
+    my ($self, $task, $vmid, $filename, $comp, $basefile) = @_;
 
     my $disks = $task->{disks};
     my @sources;
@@ -363,6 +356,7 @@ sub archive {
 
     my $bwl = $opts->{bwlimit}*1024; # bandwidth limit for cstream
     push @$cmd, [ 'cstream', '-t', $bwl ] if $opts->{bwlimit};
+    push @$cmd, [ 'pve-xdelta3', '-q', '-e', '-c', '-s', $basefile ] if $basefile;
     push @$cmd, [ split(/\s+/, $comp) ] if $comp;
 
     if ($opts->{stdout}) {
diff --git a/usr/share/perl5/PVE/VZDump/QemuServer.pm b/usr/share/perl5/PVE/VZDump/QemuServer.pm
index 70abe99..8cad998 100644
--- a/usr/share/perl5/PVE/VZDump/QemuServer.pm
+++ b/usr/share/perl5/PVE/VZDump/QemuServer.pm
@@ -243,7 +237,7 @@ sub assemble {
 }
 
 sub archive {
-    my ($self, $task, $vmid, $filename, $comp) = @_;
+    my ($self, $task, $vmid, $filename, $comp, $basefile) = @_;
 
     my $conffile = "$task->{tmpdir}/qemu-server.conf";
     my $firewall = "$task->{tmpdir}/qemu-server.fw";
@@ -353,6 +347,15 @@ sub archive {
 		die "unable to open file '$filename' - $!\n";
 	}
 
+   if ($basefile) {
+       my $basecmd = "pve-xdelta3 -e -q -c -s '$basefile'";
+       if ($comp) {
+       $comp = "$basecmd|$comp";
+       } else {
+       $comp = $basecmd;
+       }
+   }
+
 	my $outfileno;
 	if ($comp) {
 	    my @pipefd = POSIX::pipe();