* Merged the SQLite branch.

14 files changed, 832 insertions, 802 deletions

diff --git a/scripts/GeneratePatches.pm.in b/scripts/GeneratePatches.pm.in
new file mode 100755
index 000000000000..2d2653255e54
--- /dev/null
+++ b/scripts/GeneratePatches.pm.in
@@ -0,0 +1,334 @@
+#! @perl@ -w -I@libexecdir@/nix
+
+use strict;
+use File::Temp qw(tempdir);
+
+
+# Some patch generations options.
+
+# Max size of NAR archives to generate patches for.
+my $maxNarSize = $ENV{"NIX_MAX_NAR_SIZE"};
+$maxNarSize = 160 * 1024 * 1024 if !defined $maxNarSize;
+
+# If patch is bigger than this fraction of full archive, reject.
+my $maxPatchFraction = $ENV{"NIX_PATCH_FRACTION"};
+$maxPatchFraction = 0.60 if !defined $maxPatchFraction;
+
+my $timeLimit = $ENV{"NIX_BSDIFF_TIME_LIMIT"};
+$timeLimit = 180 if !defined $timeLimit;
+
+my $hashAlgo = "sha256";
+
+
+sub findOutputPaths {
+    my $narFiles = shift;
+
+    my %outPaths;
+    
+    foreach my $p (keys %{$narFiles}) {
+
+        # Ignore derivations.
+        next if ($p =~ /\.drv$/);
+        
+        # Ignore builders (too much ambiguity -- they're all called
+        # `builder.sh').
+        next if ($p =~ /\.sh$/);
+        next if ($p =~ /\.patch$/);
+        
+        # Don't bother including tar files etc.
+        next if ($p =~ /\.tar$/ || $p =~ /\.tar\.(gz|bz2|Z|lzma|xz)$/ || $p =~ /\.zip$/ || $p =~ /\.bin$/ || $p =~ /\.tgz$/ || $p =~ /\.rpm$/ || $p =~ /cvs-export$/ || $p =~ /fetchhg$/);
+
+        $outPaths{$p} = 1;
+    }
+
+    return %outPaths;
+}
+
+
+sub getNameVersion {
+    my $p = shift;
+    $p =~ /\/[0-9a-z]+((?:-[a-zA-Z][^\/-]*)+)([^\/]*)$/;
+    my $name = $1;
+    my $version = $2;
+    return undef unless defined $name && defined $version;
+    $name =~ s/^-//;
+    $version =~ s/^-//;
+    return ($name, $version);
+}
+
+
+# A quick hack to get a measure of the `distance' between two
+# versions: it's just the position of the first character that differs
+# (or 999 if they are the same).
+sub versionDiff {
+    my $s = shift;
+    my $t = shift;
+    my $i;
+    return 999 if $s eq $t;
+    for ($i = 0; $i < length $s; $i++) {
+        return $i if $i >= length $t or
+            substr($s, $i, 1) ne substr($t, $i, 1);
+    }
+    return $i;
+}
+
+
+sub getNarBz2 {
+    my $narPath = shift;
+    my $narFiles = shift;
+    my $storePath = shift;
+    
+    my $narFileList = $$narFiles{$storePath};
+    die "missing path $storePath" unless defined $narFileList;
+
+    my $narFile = @{$narFileList}[0];
+    die unless defined $narFile;
+
+    $narFile->{url} =~ /\/([^\/]+)$/;
+    die unless defined $1;
+    return "$narPath/$1";
+}
+
+
+sub containsPatch {
+    my $patches = shift;
+    my $storePath = shift;
+    my $basePath = shift;
+    my $patchList = $$patches{$storePath};
+    return 0 if !defined $patchList;
+    my $found = 0;
+    foreach my $patch (@{$patchList}) {
+        # !!! baseHash might differ
+        return 1 if $patch->{basePath} eq $basePath;
+    }
+    return 0;
+}
+
+
+sub generatePatches {
+    my ($srcNarFiles, $dstNarFiles, $srcPatches, $dstPatches, $narPath, $patchesPath, $patchesURL, $tmpDir) = @_;
+
+    my %srcOutPaths = findOutputPaths $srcNarFiles;
+    my %dstOutPaths = findOutputPaths $dstNarFiles;
+
+    # For each output path in the destination, see if we need to / can
+    # create a patch.
+
+    print STDERR "creating patches...\n";
+
+    foreach my $p (keys %dstOutPaths) {
+
+        # If exactly the same path already exists in the source, skip it.
+        next if defined $srcOutPaths{$p};
+    
+        print "  $p\n";
+
+        # If not, then we should find the paths in the source that are
+        # `most' likely to be present on a system that wants to
+        # install this path.
+
+        (my $name, my $version) = getNameVersion $p;
+        next unless defined $name && defined $version;
+
+        my @closest = ();
+        my $closestVersion;
+        my $minDist = -1; # actually, larger means closer
+
+        # Find all source paths with the same name.
+
+        foreach my $q (keys %srcOutPaths) {
+            (my $name2, my $version2) = getNameVersion $q;
+            next unless defined $name2 && defined $version2;
+
+            if ($name eq $name2) {
+
+                my $srcSystem = @{$$dstNarFiles{$p}}[0]->{system};
+                my $dstSystem = @{$$srcNarFiles{$q}}[0]->{system};
+                if (defined $srcSystem && defined $dstSystem && $srcSystem ne $dstSystem) {
+                    print "    SKIPPING $q due to different systems ($srcSystem vs. $dstSystem)\n";
+                    next;
+                }
+
+                # If the sizes differ too much, then skip.  This
+                # disambiguates between, e.g., a real component and a
+                # wrapper component (cf. Firefox in Nixpkgs).
+                my $srcSize = @{$$srcNarFiles{$q}}[0]->{size};
+                my $dstSize = @{$$dstNarFiles{$p}}[0]->{size};
+                my $ratio = $srcSize / $dstSize;
+                $ratio = 1 / $ratio if $ratio < 1;
+                # print "  SIZE $srcSize $dstSize $ratio $q\n";
+
+                if ($ratio >= 3) {
+                    print "    SKIPPING $q due to size ratio $ratio ($srcSize vs. $dstSize)\n";
+                    next;
+                }
+
+                # If there are multiple matching names, include the
+                # ones with the closest version numbers.
+                my $dist = versionDiff $version, $version2;
+                if ($dist > $minDist) {
+                    $minDist = $dist;
+                    @closest = ($q);
+                    $closestVersion = $version2;
+                } elsif ($dist == $minDist) {
+                    push @closest, $q;
+                }
+            }
+        }
+
+        if (scalar(@closest) == 0) {
+            print "    NO BASE: $p\n";
+            next;
+        }
+
+        foreach my $closest (@closest) {
+
+            # Generate a patch between $closest and $p.
+            print STDERR "  $p <- $closest\n";
+
+            # If the patch already exists, skip it.
+            if (containsPatch($srcPatches, $p, $closest) ||
+                containsPatch($dstPatches, $p, $closest))
+            {
+                print "    skipping, already exists\n";
+                next;
+            }
+
+            my $srcNarBz2 = getNarBz2 $narPath, $srcNarFiles, $closest;
+            my $dstNarBz2 = getNarBz2 $narPath, $dstNarFiles, $p;
+
+            if (! -f $srcNarBz2) {
+                warn "patch source archive $srcNarBz2 is missing\n";
+                next;
+            }
+
+            system("@bunzip2@ < $srcNarBz2 > $tmpDir/A") == 0
+                or die "cannot unpack $srcNarBz2";
+
+            if ((stat "$tmpDir/A")[7] >= $maxNarSize) {
+                print "    skipping, source is too large\n";
+                next;
+            }
+        
+            system("@bunzip2@ < $dstNarBz2 > $tmpDir/B") == 0
+                or die "cannot unpack $dstNarBz2";
+
+            if ((stat "$tmpDir/B")[7] >= $maxNarSize) {
+                print "    skipping, destination is too large\n";
+                next;
+            }
+        
+            my $time1 = time();
+            my $res = system("ulimit -t $timeLimit; @libexecdir@/bsdiff $tmpDir/A $tmpDir/B $tmpDir/DIFF");
+            my $time2 = time();
+            if ($res) {
+                warn "binary diff computation aborted after ", $time2 - $time1, " seconds\n";
+                next;
+            }
+
+            my $baseHash = `@bindir@/nix-hash --flat --type $hashAlgo --base32 $tmpDir/A` or die;
+            chomp $baseHash;
+
+            my $narHash = `@bindir@/nix-hash --flat --type $hashAlgo --base32 $tmpDir/B` or die;
+            chomp $narHash;
+
+            my $narDiffHash = `@bindir@/nix-hash --flat --type $hashAlgo --base32 $tmpDir/DIFF` or die;
+            chomp $narDiffHash;
+
+            my $narDiffSize = (stat "$tmpDir/DIFF")[7];
+            my $dstNarBz2Size = (stat $dstNarBz2)[7];
+
+            print "    size $narDiffSize; full size $dstNarBz2Size; ", $time2 - $time1, " seconds\n";
+        
+            if ($narDiffSize >= $dstNarBz2Size) {
+                print "    rejecting; patch bigger than full archive\n";
+                next;
+            }
+    
+            if ($narDiffSize / $dstNarBz2Size >= $maxPatchFraction) {
+                print "    rejecting; patch too large relative to full archive\n";
+                next;
+            }
+    
+            my $finalName = "$narDiffHash.nar-bsdiff";
+
+            if (-e "$patchesPath/$finalName") {
+                print "    not copying, already exists\n";
+            }
+
+            else {
+                system("cp '$tmpDir/DIFF' '$patchesPath/$finalName.tmp'") == 0
+                    or die "cannot copy diff";
+                rename("$patchesPath/$finalName.tmp", "$patchesPath/$finalName")
+                    or die "cannot rename $patchesPath/$finalName.tmp";
+            }
+        
+            # Add the patch to the manifest.
+            addPatch $dstPatches, $p,
+                { url => "$patchesURL/$finalName", hash => "$hashAlgo:$narDiffHash"
+                , size => $narDiffSize, basePath => $closest, baseHash => "$hashAlgo:$baseHash"
+                , narHash => "$hashAlgo:$narHash", patchType => "nar-bsdiff"
+                };
+        }
+    }
+}
+
+
+# Propagate useful patches from $srcPatches to $dstPatches.  A patch
+# is useful if it produces either paths in the $dstNarFiles or paths
+# that can be used as the base for other useful patches.
+sub propagatePatches {
+    my ($srcPatches, $dstNarFiles, $dstPatches) = @_;
+
+    print STDERR "propagating patches...\n";
+
+    my $changed;
+    do {
+        # !!! we repeat this to reach the transitive closure; inefficient
+        $changed = 0;
+
+        print STDERR "loop\n";
+
+        my %dstBasePaths;
+        foreach my $q (keys %{$dstPatches}) {
+            foreach my $patch (@{$$dstPatches{$q}}) {
+                $dstBasePaths{$patch->{basePath}} = 1;
+            }
+        }
+
+        foreach my $p (keys %{$srcPatches}) {
+            my $patchList = $$srcPatches{$p};
+
+            my $include = 0;
+
+            # Is path $p included in the destination?  If so, include
+            # patches that produce it.
+            $include = 1 if defined $$dstNarFiles{$p};
+
+            # Is path $p a path that serves as a base for paths in the
+            # destination?  If so, include patches that produce it.
+            # !!! check baseHash
+            $include = 1 if defined $dstBasePaths{$p};
+
+            if ($include) {
+                foreach my $patch (@{$patchList}) {
+                    $changed = 1 if addPatch $dstPatches, $p, $patch;
+                }
+            }
+        
+        }
+    
+    } while $changed;
+}
+
+
+# Add all new patches in $srcPatches to $dstPatches.
+sub copyPatches {
+    my ($srcPatches, $dstPatches) = @_;
+    foreach my $p (keys %{$srcPatches}) {
+        addPatch $dstPatches, $p, $_ foreach @{$$srcPatches{$p}};
+    }
+}
+
+
+return 1;
diff --git a/scripts/Makefile.am b/scripts/Makefile.am
index aa5d6f78c18a..60bb0a9b8105 100644
--- a/scripts/Makefile.am
+++ b/scripts/Makefile.am
@@ -1,23 +1,23 @@
 bin_SCRIPTS = nix-collect-garbage \
   nix-pull nix-push nix-prefetch-url \
   nix-install-package nix-channel nix-build \
-  nix-copy-closure 
+  nix-copy-closure nix-generate-patches
 
-noinst_SCRIPTS = nix-profile.sh generate-patches.pl \
+noinst_SCRIPTS = nix-profile.sh GeneratePatches.pm \
   find-runtime-roots.pl build-remote.pl nix-reduce-build \
   copy-from-other-stores.pl nix-http-export.cgi
 
-nix-pull nix-push: readmanifest.pm readconfig.pm download-using-manifests.pl
+nix-pull nix-push: NixManifest.pm NixConfig.pm download-using-manifests.pl
 
-install-exec-local: readmanifest.pm download-using-manifests.pl copy-from-other-stores.pl find-runtime-roots.pl
+install-exec-local: NixManifest.pm GeneratePatches.pm download-using-manifests.pl copy-from-other-stores.pl find-runtime-roots.pl
 	$(INSTALL) -d $(DESTDIR)$(sysconfdir)/profile.d
 	$(INSTALL_PROGRAM) nix-profile.sh $(DESTDIR)$(sysconfdir)/profile.d/nix.sh
 	$(INSTALL) -d $(DESTDIR)$(libexecdir)/nix
-	$(INSTALL_DATA) readmanifest.pm $(DESTDIR)$(libexecdir)/nix 
-	$(INSTALL_DATA) readconfig.pm $(DESTDIR)$(libexecdir)/nix 
-	$(INSTALL_DATA) ssh.pm $(DESTDIR)$(libexecdir)/nix 
+	$(INSTALL_DATA) NixManifest.pm $(DESTDIR)$(libexecdir)/nix 
+	$(INSTALL_DATA) NixConfig.pm $(DESTDIR)$(libexecdir)/nix 
+	$(INSTALL_DATA) SSH.pm $(DESTDIR)$(libexecdir)/nix 
+	$(INSTALL_DATA) GeneratePatches.pm $(DESTDIR)$(libexecdir)/nix 
 	$(INSTALL_PROGRAM) find-runtime-roots.pl $(DESTDIR)$(libexecdir)/nix 
-	$(INSTALL_PROGRAM) generate-patches.pl $(DESTDIR)$(libexecdir)/nix 
 	$(INSTALL_PROGRAM) build-remote.pl $(DESTDIR)$(libexecdir)/nix 
 	$(INSTALL) -d $(DESTDIR)$(libexecdir)/nix/substituters
 	$(INSTALL_PROGRAM) download-using-manifests.pl $(DESTDIR)$(libexecdir)/nix/substituters
@@ -30,15 +30,16 @@ EXTRA_DIST = nix-collect-garbage.in \
   nix-pull.in nix-push.in nix-profile.sh.in \
   nix-prefetch-url.in nix-install-package.in \
   nix-channel.in \
-  readmanifest.pm.in \
-  readconfig.pm.in \
-  ssh.pm \
+  NixManifest.pm.in \
+  NixConfig.pm.in \
+  SSH.pm \
+  GeneratePatches.pm.in \
   nix-build.in \
   download-using-manifests.pl.in \
   copy-from-other-stores.pl.in \
-  generate-patches.pl.in \
   nix-copy-closure.in \
   find-runtime-roots.pl.in \
   build-remote.pl.in \
   nix-reduce-build.in \
-  nix-http-export.cgi.in 
+  nix-http-export.cgi.in \
+  nix-generate-patches.in
diff --git a/scripts/readconfig.pm.in b/scripts/NixConfig.pm.in
index aeb443aeed3a..aeb443aeed3a 100644
--- a/scripts/readconfig.pm.in
+++ b/scripts/NixConfig.pm.in
diff --git a/scripts/readmanifest.pm.in b/scripts/NixManifest.pm.in
index 7244984ead6a..be0dda616922 100644
--- a/scripts/readmanifest.pm.in
+++ b/scripts/NixManifest.pm.in
@@ -33,18 +33,8 @@ sub readManifest {
 
     my $manifestVersion = 2;
 
-    my $storePath;
-    my $url;
-    my $hash;
-    my $size;
-    my $basePath;
-    my $baseHash;
-    my $patchType;
-    my $narHash;
-    my $references;
-    my $deriver;
-    my $hashAlgo;
-    my $copyFrom;
+    my ($storePath, $url, $hash, $size, $basePath, $baseHash, $patchType);
+    my ($narHash, $narSize, $references, $deriver, $hashAlgo, $copyFrom, $system);
 
     while (<MANIFEST>) {
         chomp;
@@ -62,9 +52,11 @@ sub readManifest {
                 undef $hash;
                 undef $size;
                 undef $narHash;
+                undef $narSize;
                 undef $basePath;
                 undef $baseHash;
                 undef $patchType;
+                undef $system;
                 $references = "";
                 $deriver = "";
                 $hashAlgo = "md5";
@@ -89,8 +81,10 @@ sub readManifest {
                     if (!$found) {
                         push @{$narFileList},
                             { url => $url, hash => $hash, size => $size
-                            , narHash => $narHash, references => $references
+                            , narHash => $narHash, narSize => $narSize
+                            , references => $references
                             , deriver => $deriver, hashAlgo => $hashAlgo
+                            , system => $system
                             };
                     }
                 
@@ -100,8 +94,8 @@ sub readManifest {
                     addPatch $patches, $storePath,
                         { url => $url, hash => $hash, size => $size
                         , basePath => $basePath, baseHash => $baseHash
-                        , narHash => $narHash, patchType => $patchType
-                        , hashAlgo => $hashAlgo
+                        , narHash => $narHash, narSize => $narSize
+                        , patchType => $patchType, hashAlgo => $hashAlgo
                         };
                 }
 
@@ -132,9 +126,11 @@ sub readManifest {
             elsif (/^\s*BaseHash:\s*(\S+)\s*$/) { $baseHash = $1; }
             elsif (/^\s*Type:\s*(\S+)\s*$/) { $patchType = $1; }
             elsif (/^\s*NarHash:\s*(\S+)\s*$/) { $narHash = $1; }
+            elsif (/^\s*NarSize:\s*(\d+)\s*$/) { $narSize = $1; }
             elsif (/^\s*References:\s*(.*)\s*$/) { $references = $1; }
             elsif (/^\s*Deriver:\s*(\S+)\s*$/) { $deriver = $1; }
             elsif (/^\s*ManifestVersion:\s*(\d+)\s*$/) { $manifestVersion = $1; }
+            elsif (/^\s*System:\s*(\S+)\s*$/) { $system = $1; }
 
             # Compatibility;
             elsif (/^\s*NarURL:\s*(\S+)\s*$/) { $url = $1; }
@@ -150,7 +146,7 @@ sub readManifest {
 
 
 sub writeManifest {
-    my ($manifest, $narFiles, $patches) = @_;
+    my ($manifest, $narFiles, $patches, $noCompress) = @_;
 
     open MANIFEST, ">$manifest.tmp"; # !!! check exclusive
 
@@ -165,12 +161,14 @@ sub writeManifest {
             print MANIFEST "  StorePath: $storePath\n";
             print MANIFEST "  NarURL: $narFile->{url}\n";
             print MANIFEST "  Hash: $narFile->{hash}\n" if defined $narFile->{hash};
-            print MANIFEST "  NarHash: $narFile->{narHash}\n";
             print MANIFEST "  Size: $narFile->{size}\n" if defined $narFile->{size};
+            print MANIFEST "  NarHash: $narFile->{narHash}\n";
+            print MANIFEST "  NarSize: $narFile->{narSize}\n" if $narFile->{narSize};
             print MANIFEST "  References: $narFile->{references}\n"
                 if defined $narFile->{references} && $narFile->{references} ne "";
             print MANIFEST "  Deriver: $narFile->{deriver}\n"
                 if defined $narFile->{deriver} && $narFile->{deriver} ne "";
+            print MANIFEST "  System: $narFile->{system}\n" if defined $narFile->{system};
             print MANIFEST "}\n";
         }
     }
@@ -182,8 +180,9 @@ sub writeManifest {
             print MANIFEST "  StorePath: $storePath\n";
             print MANIFEST "  NarURL: $patch->{url}\n";
             print MANIFEST "  Hash: $patch->{hash}\n";
-            print MANIFEST "  NarHash: $patch->{narHash}\n";
             print MANIFEST "  Size: $patch->{size}\n";
+            print MANIFEST "  NarHash: $patch->{narHash}\n";
+            print MANIFEST "  NarSize: $patch->{narSize}\n" if $patch->{narSize};
             print MANIFEST "  BasePath: $patch->{basePath}\n";
             print MANIFEST "  BaseHash: $patch->{baseHash}\n";
             print MANIFEST "  Type: $patch->{patchType}\n";
@@ -199,11 +198,13 @@ sub writeManifest {
 
 
     # Create a bzipped manifest.
-    system("@bzip2@ < $manifest > $manifest.bz2.tmp") == 0
-        or die "cannot compress manifest";
+    unless (defined $noCompress) {
+	system("@bzip2@ < $manifest > $manifest.bz2.tmp") == 0
+	    or die "cannot compress manifest";
 
-    rename("$manifest.bz2.tmp", "$manifest.bz2")
-        or die "cannot rename $manifest.bz2.tmp: $!";
+	rename("$manifest.bz2.tmp", "$manifest.bz2")
+	    or die "cannot rename $manifest.bz2.tmp: $!";
+    }
 }
 
 
diff --git a/scripts/ssh.pm b/scripts/SSH.pm
index c6d667a65d90..68f4a628b072 100644
--- a/scripts/ssh.pm
+++ b/scripts/SSH.pm
@@ -3,6 +3,8 @@ use File::Temp qw(tempdir);
 
 our @sshOpts = split ' ', ($ENV{"NIX_SSHOPTS"} or "");
 
+push @sshOpts, "-x";
+
 my $sshStarted = 0;
 my $sshHost;
 
@@ -24,14 +26,17 @@ sub openSSHConnection {
     # child continues to run if we are killed.  So instead make SSH
     # print "started" when it has established the connection, and wait
     # until we see that.
-    open SSH, "ssh $sshHost @sshOpts -M -N -o LocalCommand='echo started' -o PermitLocalCommand=yes |" or die;
-    while (<SSH>) {
+    open SSHPIPE, "ssh $sshHost @sshOpts -M -N -o LocalCommand='echo started' -o PermitLocalCommand=yes |" or die;
+
+    while (<SSHPIPE>) {
         chomp;
-        last if /started/;
+        if ($_ eq "started") {
+            $sshStarted = 1;
+            return 1;
+        }
     }
-    
-    $sshStarted = 1;
-    return 1;
+
+    return 0;
 }
 
 # Tell the master SSH client to exit.
diff --git a/scripts/build-remote.pl.in b/scripts/build-remote.pl.in
index c440b6a0f142..e943b0d9e304 100755
--- a/scripts/build-remote.pl.in
+++ b/scripts/build-remote.pl.in
@@ -3,7 +3,8 @@
 use Fcntl ':flock';
 use English '-no_match_vars';
 use IO::Handle;
-use ssh qw/sshOpts openSSHConnection/;
+use SSH qw/sshOpts openSSHConnection/;
+no warnings('once');
 
 
 # General operation:
@@ -31,57 +32,22 @@ $ENV{"DISPLAY"} = "";
 $ENV{"SSH_ASKPASS"} = "";
 
 
-my $loadIncreased = 0;
-
-my ($amWilling, $localSystem, $neededSystem, $drvPath, $maxSilentTime) = @ARGV;
-$maxSilentTime = 0 unless defined $maxSilentTime;
-
 sub sendReply {
     my $reply = shift;
     print STDERR "# $reply\n";
 }
 
-sub decline {
-    sendReply "decline";
-    exit 0;
-}
-
-my $currentLoad = $ENV{"NIX_CURRENT_LOAD"};
-decline unless defined $currentLoad;
-mkdir $currentLoad, 0777 or die unless -d $currentLoad;
-
-my $conf = $ENV{"NIX_REMOTE_SYSTEMS"};
-decline if !defined $conf || ! -e $conf;
-
-my $canBuildLocally = $amWilling && ($localSystem eq $neededSystem);
-
+sub all { $_ || return 0 for @_; 1 }
 
-# Read the list of machines.
-my @machines;
-open CONF, "< $conf" or die;
-
-while (<CONF>) {
-    chomp;
-    s/\#.*$//g;
-    next if /^\s*$/;
-    /^\s*(\S+)\s+(\S+)\s+(\S+)\s+(\d+)(\s+([0-9\.]+))?\s*$/ or die;
-    push @machines,
-        { hostName => $1
-        , systemTypes => [split(/,/, $2)]
-        , sshKeys => $3
-        , maxJobs => $4
-        , speedFactor => 1.0 * ($6 || 1)
-        , enabled => 1
-        };
-}
 
-close CONF;
+# Initialisation.
+my $loadIncreased = 0;
 
+my ($localSystem, $maxSilentTime, $printBuildTrace) = @ARGV;
+$maxSilentTime = 0 unless defined $maxSilentTime;
 
-# Acquire the exclusive lock on $currentLoad/main-lock.
-my $mainLock = "$currentLoad/main-lock";
-open MAINLOCK, ">>$mainLock" or die;
-flock(MAINLOCK, LOCK_EX) or die;
+my $currentLoad = $ENV{"NIX_CURRENT_LOAD"};
+my $conf = $ENV{"NIX_REMOTE_SYSTEMS"};
 
 
 sub openSlotLock {
@@ -91,150 +57,213 @@ sub openSlotLock {
     open $slotLock, ">>$slotLockFn" or die;
     return $slotLock;
 }
-    
 
-my $hostName;
-my $slotLock;
 
-while (1) {
+# Read the list of machines.
+my @machines;
+if (defined $conf && -e $conf) {
+    open CONF, "< $conf" or die;
+    while (<CONF>) {
+        chomp;
+        s/\#.*$//g;
+        next if /^\s*$/;
+        my @tokens = split /\s/, $_;
+        push @machines,
+            { hostName => $tokens[0]
+            , systemTypes => [ split(/,/, $tokens[1]) ]
+            , sshKeys => $tokens[2]
+            , maxJobs => int($tokens[3])
+            , speedFactor => 1.0 * (defined $tokens[4] ? int($tokens[4]) : 1)
+            , features => [ split(/,/, $tokens[5] || "") ]
+            , enabled => 1
+            };
+    }
+    close CONF;
+}
+
+
+
+# Wait for the calling process to ask us whether we can build some derivation.
+my ($drvPath, $hostName, $slotLock);
+
+REQ: while (1) {
+    $_ = <STDIN> || exit 0;
+    my ($amWilling, $neededSystem);
+    ($amWilling, $neededSystem, $drvPath, $requiredFeatures) = split;
+    my @requiredFeatures = split /,/, $requiredFeatures;
+
+    my $canBuildLocally = $amWilling && ($localSystem eq $neededSystem);
+
+    if (!defined $currentLoad) {
+        sendReply "decline";
+        next;
+    }
+    
+    # Acquire the exclusive lock on $currentLoad/main-lock.
+    mkdir $currentLoad, 0777 or die unless -d $currentLoad;
+    my $mainLock = "$currentLoad/main-lock";
+    open MAINLOCK, ">>$mainLock" or die;
+    flock(MAINLOCK, LOCK_EX) or die;
     
-    # Find all machine that can execute this build, i.e., that support
-    # builds for the given platform and are not at their job limit.
-    my $rightType = 0;
-    my @available = ();
-    LOOP: foreach my $cur (@machines) {
-        if ($cur->{enabled} && grep { $neededSystem eq $_ } @{$cur->{systemTypes}}) {
-            $rightType = 1;
-
-            # We have a machine of the right type.  Determine the load on
-            # the machine.
-            my $slot = 0;
-            my $load = 0;
-            my $free;
-            while ($slot < $cur->{maxJobs}) {
-                my $slotLock = openSlotLock($cur, $slot);
-                if (flock($slotLock, LOCK_EX | LOCK_NB)) {
-                    $free = $slot unless defined $free;
-                    flock($slotLock, LOCK_UN) or die;
-                } else {
-                    $load++;
+    
+    while (1) {
+        # Find all machine that can execute this build, i.e., that
+        # support builds for the given platform and features, and are
+        # not at their job limit.
+        my $rightType = 0;
+        my @available = ();
+        LOOP: foreach my $cur (@machines) {
+            if ($cur->{enabled}
+                && (grep { $neededSystem eq $_ } @{$cur->{systemTypes}})
+                && all(map { my $f = $_; 0 != grep { $f eq $_ } @{$cur->{features}} } @requiredFeatures))
+            {
+                $rightType = 1;
+
+                # We have a machine of the right type.  Determine the load on
+                # the machine.
+                my $slot = 0;
+                my $load = 0;
+                my $free;
+                while ($slot < $cur->{maxJobs}) {
+                    my $slotLock = openSlotLock($cur, $slot);
+                    if (flock($slotLock, LOCK_EX | LOCK_NB)) {
+                        $free = $slot unless defined $free;
+                        flock($slotLock, LOCK_UN) or die;
+                    } else {
+                        $load++;
+                    }
+                    close $slotLock;
+                    $slot++;
                 }
-                close $slotLock;
-                $slot++;
+                
+                push @available, { machine => $cur, load => $load, free => $free }
+                if $load < $cur->{maxJobs};
             }
-
-            push @available, { machine => $cur, load => $load, free => $free }
-            if $load < $cur->{maxJobs};
         }
-    }
 
-    if (defined $ENV{NIX_DEBUG_HOOK}) {
-        print STDERR "load on " . $_->{machine}->{hostName} . " = " . $_->{load} . "\n"
-            foreach @available;
-    }
+        if (defined $ENV{NIX_DEBUG_HOOK}) {
+            print STDERR "load on " . $_->{machine}->{hostName} . " = " . $_->{load} . "\n"
+                foreach @available;
+        }
 
 
-    # Didn't find any available machine?  Then decline or postpone.
-    if (scalar @available == 0) {
-        # Postpone if we have a machine of the right type, except if the
-        # local system can and wants to do the build.
-        if ($rightType && !$canBuildLocally) {
-            sendReply "postpone";
-            exit 0;
-        } else {
-            decline;
+        # Didn't find any available machine?  Then decline or postpone.
+        if (scalar @available == 0) {
+            # Postpone if we have a machine of the right type, except
+            # if the local system can and wants to do the build.
+            if ($rightType && !$canBuildLocally) {
+                sendReply "postpone";
+            } else {
+                sendReply "decline";                
+            }
+            close MAINLOCK;
+            next REQ;
         }
-    }
-
 
-    # Prioritise the available machines as follows:
-    # - First by load divided by speed factor, rounded to the nearest
-    #   integer.  This causes fast machines to be preferred over slow
-    #   machines with similar loads.
-    # - Then by speed factor.
-    # - Finally by load.
-    sub lf { my $x = shift; return int($x->{load} / $x->{machine}->{speedFactor} + 0.4999); }
-    @available = sort
-        { lf($a) <=> lf($b)
-              || $b->{machine}->{speedFactor} <=> $a->{machine}->{speedFactor}
-              || $a->{load} <=> $b->{load}
-        } @available;
 
+        # Prioritise the available machines as follows:
+        # - First by load divided by speed factor, rounded to the nearest
+        #   integer.  This causes fast machines to be preferred over slow
+        #   machines with similar loads.
+        # - Then by speed factor.
+        # - Finally by load.
+        sub lf { my $x = shift; return int($x->{load} / $x->{machine}->{speedFactor} + 0.4999); }
+        @available = sort
+            { lf($a) <=> lf($b)
+                  || $b->{machine}->{speedFactor} <=> $a->{machine}->{speedFactor}
+                  || $a->{load} <=> $b->{load}
+            } @available;
 
-    # Select the best available machine and lock a free slot.
-    my $selected = $available[0]; 
-    my $machine = $selected->{machine};
 
-    $slotLock = openSlotLock($machine, $selected->{free});
-    flock($slotLock, LOCK_EX | LOCK_NB) or die;
-    utime undef, undef, $slotLock;
+        # Select the best available machine and lock a free slot.
+        my $selected = $available[0]; 
+        my $machine = $selected->{machine};
+        
+        $slotLock = openSlotLock($machine, $selected->{free});
+        flock($slotLock, LOCK_EX | LOCK_NB) or die;
+        utime undef, undef, $slotLock;
 
-    close MAINLOCK;
+        close MAINLOCK;
 
 
-    # Connect to the selected machine.
-    @sshOpts = ("-i", $machine->{sshKeys}, "-x");
-    $hostName = $machine->{hostName};
-    last if openSSHConnection $hostName;
+        # Connect to the selected machine.
+        @sshOpts = ("-i", $machine->{sshKeys}, "-x");
+        $hostName = $machine->{hostName};
+        last REQ if openSSHConnection $hostName;
     
-    warn "unable to open SSH connection to $hostName, trying other available machines...\n";
-    $machine->{enabled} = 0;
+        warn "unable to open SSH connection to $hostName, trying other available machines...\n";
+        $machine->{enabled} = 0;
+    }
 }
 
 
 # Tell Nix we've accepted the build.
 sendReply "accept";
-my $x = <STDIN>;
-chomp $x;
-
-if ($x ne "okay") {
-    exit 0;
-}
+my @inputs = split /\s/, readline(STDIN);
+my @outputs = split /\s/, readline(STDIN);
 
 
-# Do the actual build.
 print STDERR "building `$drvPath' on `$hostName'\n";
+print STDERR "@ build-remote $drvPath $hostName\n" if $printBuildTrace;
 
-my $inputs = `cat inputs`; die if ($? != 0);
-$inputs =~ s/\n/ /g;
-
-my $outputs = `cat outputs`; die if ($? != 0);
-$outputs =~ s/\n/ /g;
-
-print "copying inputs...\n";
 
 my $maybeSign = "";
 $maybeSign = "--sign" if -e "/nix/etc/nix/signing-key.sec";
 
-system("NIX_SSHOPTS=\"@sshOpts\" @bindir@/nix-copy-closure $hostName $maybeSign $drvPath $inputs") == 0
+
+# Register the derivation as a temporary GC root.  Note that $PPID is
+# the PID of the remote SSH process, which, due to the use of a
+# persistant SSH connection, should be the same across all remote
+# command invocations for this session.
+my $rootsDir = "@localstatedir@/nix/gcroots/tmp";
+system("ssh $hostName @sshOpts 'mkdir -m 1777 -p $rootsDir; ln -sfn $drvPath $rootsDir/\$PPID.drv'");
+
+sub removeRoots {
+    system("ssh $hostName @sshOpts 'rm -f $rootsDir/\$PPID.drv $rootsDir/\$PPID.out'");
+}
+
+
+# Copy the derivation and its dependencies to the build machine.
+system("NIX_SSHOPTS=\"@sshOpts\" @bindir@/nix-copy-closure $hostName $maybeSign $drvPath @inputs") == 0
     or die "cannot copy inputs to $hostName: $?";
 
-print "building...\n";
-
-my $buildFlags = "--max-silent-time $maxSilentTime --fallback";
-
-# `-tt' forces allocation of a pseudo-terminal.  This is required to
-# make the remote nix-store process receive a signal when the
-# connection dies.  Without it, the remote process might continue to
-# run indefinitely (that is, until it next tries to write to
-# stdout/stderr).
-if (system("ssh $hostName @sshOpts -tt 'nix-store -r $drvPath $buildFlags > /dev/null'") != 0) {
-    # If we couldn't run ssh or there was an ssh problem (indicated by
-    # exit code 255), then we return exit code 1; otherwise we assume
-    # that the builder failed, which we indicate to Nix using exit
-    # code 100.  It's important to distinguish between the two because
-    # the first is a transient failure and the latter is permanent.
-    my $res = $? == -1 || ($? >> 8) == 255 ? 1 : 100;
-    print STDERR "build of `$drvPath' on `$hostName' failed with exit code $?\n";
+
+# Perform the build.
+my $buildFlags = "--max-silent-time $maxSilentTime --fallback --add-root $rootsDir/\$PPID.out --option verbosity 0";
+
+# We let the remote side kill its process group when the connection is
+# closed unexpectedly.  This is necessary to ensure that no processes
+# are left running on the remote system if the local Nix process is
+# killed.  (SSH itself doesn't kill child processes if the connection
+# is interrupted unless the `-tt' flag is used to force a pseudo-tty,
+# in which case every child receives SIGHUP; however, `-tt' doesn't
+# work on some platforms when connection sharing is used.)
+pipe STDIN, DUMMY; # make sure we have a readable STDIN
+if (system("ssh $hostName @sshOpts '(read; kill -INT -\$\$) <&0 & nix-store -r $drvPath $buildFlags > /dev/null' 2>&4") != 0) {
+    # Note that if we get exit code 100 from `nix-store -r', it
+    # denotes a permanent build failure (as opposed to an SSH problem
+    # or a temporary Nix problem).  We propagate this to the caller to
+    # allow it to distinguish between transient and permanent
+    # failures.
+    my $res = $? >> 8;
+    print STDERR "build of `$drvPath' on `$hostName' failed with exit code $res\n";
+    removeRoots;
     exit $res;
 }
 
-print "build of `$drvPath' on `$hostName' succeeded\n";
+#print "build of `$drvPath' on `$hostName' succeeded\n";
 
-foreach my $output (split '\n', $outputs) {
+
+# Copy the output from the build machine.
+foreach my $output (@outputs) {
     my $maybeSignRemote = "";
     $maybeSignRemote = "--sign" if $UID != 0;
     
-    system("ssh $hostName @sshOpts 'nix-store --export $maybeSignRemote $output' | @bindir@/nix-store --import > /dev/null") == 0
+    system("ssh $hostName @sshOpts 'nix-store --export $maybeSignRemote $output'" .
+           "| NIX_HELD_LOCKS=$output @bindir@/nix-store --import > /dev/null") == 0
 	or die "cannot copy $output from $hostName: $?";
 }
+
+
+# Get rid of the temporary GC roots.
+removeRoots;
diff --git a/scripts/copy-from-other-stores.pl.in b/scripts/copy-from-other-stores.pl.in
index 8f0ff4ca8df8..10130c0893ea 100644
--- a/scripts/copy-from-other-stores.pl.in
+++ b/scripts/copy-from-other-stores.pl.in
@@ -17,25 +17,19 @@ foreach my $dir (@remoteStoresAll) {
 }
 
 
+$ENV{"NIX_REMOTE"} = "";
+
+
 sub findStorePath {
     my $storePath = shift;
-    
-    my $storePathName = basename $storePath;
-    
     foreach my $store (@remoteStores) {
-        # Determine whether $storePath exists by looking for the
-        # existence of the info file, and if so, get store path info
-        # from that file.  This rather breaks abstraction: we should
-        # be using `nix-store' for that.  But right now there is no
-        # good way to tell nix-store to access a store mounted under a
-        # different location (there's $NIX_STORE, but that only works
-        # if the remote store is mounted under its "real" location).
-        my $infoFile = "$store/var/nix/db/info/$storePathName";
-        my $storePath2 = "$store/store/$storePathName";
-        if (-f $infoFile && -e $storePath2) {
-            return ($infoFile, $storePath2);
-        }
+        my $sourcePath = "$store/store/" . basename $storePath;
+        next unless -e $sourcePath || -l $sourcePath;
+        $ENV{"NIX_DB_DIR"} = "$store/var/nix/db";
+        return ($store, $sourcePath) if
+            system("@bindir@/nix-store --check-validity $storePath") == 0;
     }
+    return undef;
 }
 
 
@@ -46,37 +40,38 @@ if ($ARGV[0] eq "--query") {
 
         if ($cmd eq "have") {
             my $storePath = <STDIN>; chomp $storePath;
-            (my $infoFile) = findStorePath $storePath;
-            print STDOUT ($infoFile ? "1\n" : "0\n");
+            print STDOUT (defined findStorePath($storePath) ? "1\n" : "0\n");
         }
 
         elsif ($cmd eq "info") {
             my $storePath = <STDIN>; chomp $storePath;
-            (my $infoFile) = findStorePath $storePath;
-            if (!$infoFile) {
+            my ($store, $sourcePath) = findStorePath($storePath);
+            if (!defined $store) {
                 print "0\n";
                 next; # not an error
             }
             print "1\n";
 
-            my $deriver = "";
-            my @references = ();
-
-            open INFO, "<$infoFile" or die "cannot read info file $infoFile\n";
-            while (<INFO>) {
-                chomp;
-                /^([\w-]+): (.*)$/ or die "bad info file";
-                my $key = $1;
-                my $value = $2;
-                if ($key eq "Deriver") { $deriver = $value; }
-                elsif ($key eq "References") { @references = split ' ', $value; }
-            }
-            close INFO;
+            $ENV{"NIX_DB_DIR"} = "$store/var/nix/db";
+            
+            my $deriver = `@bindir@/nix-store --query --deriver $storePath`;
+            die "cannot query deriver of `$storePath'" if $? != 0;
+            chomp $deriver;
+            $deriver = "" if $deriver eq "unknown-deriver";
+
+            my @references = split "\n",
+                `@bindir@/nix-store --query --references $storePath`;
+            die "cannot query references of `$storePath'" if $? != 0;
+
+            my $narSize = `@bindir@/nix-store --query --size $storePath`;
+            die "cannot query size of `$storePath'" if $? != 0;
+            chomp $narSize;
 
             print "$deriver\n";
             print scalar @references, "\n";
             print "$_\n" foreach @references;
-            print "0\n"; # !!! showing size not supported (yet)
+            print "$narSize\n";
+            print "$narSize\n";
         }
 
         else { die "unknown command `$cmd'"; }
@@ -87,8 +82,8 @@ if ($ARGV[0] eq "--query") {
 elsif ($ARGV[0] eq "--substitute") {
     die unless scalar @ARGV == 2;
     my $storePath = $ARGV[1];
-    (my $infoFile, my $sourcePath) = findStorePath $storePath;
-    die unless $infoFile;
+    my ($store, $sourcePath) = findStorePath $storePath;
+    die unless $store;
     print "\n*** Copying `$storePath' from `$sourcePath'\n\n";
     system("$binDir/nix-store --dump $sourcePath | $binDir/nix-store --restore $storePath") == 0
         or die "cannot copy `$sourcePath' to `$storePath'";
diff --git a/scripts/download-using-manifests.pl.in b/scripts/download-using-manifests.pl.in
index d48c7dd4bc3f..fe80bc11f3a7 100644
--- a/scripts/download-using-manifests.pl.in
+++ b/scripts/download-using-manifests.pl.in
@@ -1,7 +1,7 @@
 #! @perl@ -w -I@libexecdir@/nix
 
 use strict;
-use readmanifest;
+use NixManifest;
 use POSIX qw(strftime);
 use File::Temp qw(tempdir);
 
@@ -12,6 +12,10 @@ STDOUT->autoflush(1);
 my $manifestDir = ($ENV{"NIX_MANIFESTS_DIR"} or "@localstatedir@/nix/manifests");
 my $logFile = "@localstatedir@/log/nix/downloads";
 
+# For queries, skip expensive calls to nix-hash etc.  We're just
+# estimating the expected download size.
+my $fast = 1;
+
 
 # Load all manifests.
 my %narFiles;
@@ -31,6 +35,151 @@ for my $manifest (glob "$manifestDir/*.nixmanifest") {
 }
 
 
+sub isValidPath {
+    my $p = shift;
+    if ($fast) {
+        return -e $p;
+    } else {
+        return system("$binDir/nix-store --check-validity '$p' 2> /dev/null") == 0;
+    }
+}
+
+
+sub parseHash {
+    my $hash = shift;
+    if ($hash =~ /^(.+):(.+)$/) {
+        return ($1, $2);
+    } else {
+        return ("md5", $hash);
+    }
+}
+
+
+# Compute the most efficient sequence of downloads to produce the
+# given path.
+sub computeSmallestDownload {
+    my $targetPath = shift;
+    
+    # Build a graph of all store paths that might contribute to the
+    # construction of $targetPath, and the special node "start".  The
+    # edges are either patch operations, or downloads of full NAR
+    # files.  The latter edges only occur between "start" and a store
+    # path.
+    my %graph;
+
+    $graph{"start"} = {d => 0, pred => undef, edges => []};
+
+    my @queue = ();
+    my $queueFront = 0;
+    my %done;
+
+    sub addNode {
+        my $graph = shift;
+        my $u = shift;
+        $$graph{$u} = {d => 999999999999, pred => undef, edges => []}
+            unless defined $$graph{$u};
+    }
+
+    sub addEdge {
+        my $graph = shift;
+        my $u = shift;
+        my $v = shift;
+        my $w = shift;
+        my $type = shift;
+        my $info = shift;
+        addNode $graph, $u;
+        push @{$$graph{$u}->{edges}},
+            {weight => $w, start => $u, end => $v, type => $type, info => $info};
+        my $n = scalar @{$$graph{$u}->{edges}};
+    }
+
+    push @queue, $targetPath;
+
+    while ($queueFront < scalar @queue) {
+        my $u = $queue[$queueFront++];
+        next if defined $done{$u};
+        $done{$u} = 1;
+
+        addNode \%graph, $u;
+
+        # If the path already exists, it has distance 0 from the
+        # "start" node.
+        if (isValidPath($u)) {
+            addEdge \%graph, "start", $u, 0, "present", undef;
+        }
+
+        else {
+
+            # Add patch edges.
+            my $patchList = $patches{$u};
+            foreach my $patch (@{$patchList}) {
+                if (isValidPath($patch->{basePath})) {
+                    # !!! this should be cached
+                    my ($baseHashAlgo, $baseHash) = parseHash $patch->{baseHash};
+                    my $format = "--base32";
+                    $format = "" if $baseHashAlgo eq "md5";
+                    my $hash = $fast && $baseHashAlgo eq "sha256"
+                        ? `$binDir/nix-store -q --hash "$patch->{basePath}"`
+                        : `$binDir/nix-hash --type '$baseHashAlgo' $format "$patch->{basePath}"`;
+                    chomp $hash;
+                    $hash =~ s/.*://;
+                    next if $hash ne $baseHash;
+                }
+                push @queue, $patch->{basePath};
+                addEdge \%graph, $patch->{basePath}, $u, $patch->{size}, "patch", $patch;
+            }
+
+            # Add NAR file edges to the start node.
+            my $narFileList = $narFiles{$u};
+            foreach my $narFile (@{$narFileList}) {
+                # !!! how to handle files whose size is not known in advance?
+                # For now, assume some arbitrary size (1 MB).
+                addEdge \%graph, "start", $u, ($narFile->{size} || 1000000), "narfile", $narFile;
+            }
+        }
+    }
+
+
+    # Run Dijkstra's shortest path algorithm to determine the shortest
+    # sequence of download and/or patch actions that will produce
+    # $targetPath.
+
+    my @todo = keys %graph;
+
+    while (scalar @todo > 0) {
+
+        # Remove the closest element from the todo list.
+        # !!! inefficient, use a priority queue
+        @todo = sort { -($graph{$a}->{d} <=> $graph{$b}->{d}) } @todo;
+        my $u = pop @todo;
+
+        my $u_ = $graph{$u};
+
+        foreach my $edge (@{$u_->{edges}}) {
+            my $v_ = $graph{$edge->{end}};
+            if ($v_->{d} > $u_->{d} + $edge->{weight}) {
+                $v_->{d} = $u_->{d} + $edge->{weight};
+                # Store the edge; to edge->start is actually the
+                # predecessor.
+                $v_->{pred} = $edge; 
+            }
+        }
+    }
+
+
+    # Retrieve the shortest path from "start" to $targetPath.
+    my @path = ();
+    my $cur = $targetPath;
+    return () unless defined $graph{$targetPath}->{pred};
+    while ($cur ne "start") {
+        push @path, $graph{$cur}->{pred};
+        $cur = $graph{$cur}->{pred}->{start};
+    }
+
+    return @path;
+}
+
+
 # Parse the arguments.
 
 if ($ARGV[0] eq "--query") {
@@ -46,6 +195,7 @@ if ($ARGV[0] eq "--query") {
 
         elsif ($cmd eq "info") {
             my $storePath = <STDIN>; chomp $storePath;
+
             my $info;
             if (defined $narFiles{$storePath}) {
                 $info = @{$narFiles{$storePath}}[0];
@@ -57,13 +207,32 @@ if ($ARGV[0] eq "--query") {
                 print "0\n";
                 next; # not an error
             }
+
             print "1\n";
             print "$info->{deriver}\n";
             my @references = split " ", $info->{references};
             print scalar @references, "\n";
             print "$_\n" foreach @references;
-            my $size = $info->{size} || 0;
-            print "$size\n";
+
+            my @path = computeSmallestDownload $storePath;
+            
+            my $downloadSize = 0;
+            while (scalar @path > 0) {
+                my $edge = pop @path;
+                my $u = $edge->{start};
+                my $v = $edge->{end};
+                if ($edge->{type} eq "patch") {
+                    $downloadSize += $edge->{info}->{size} || 0;
+                }
+                elsif ($edge->{type} eq "narfile") {
+                    $downloadSize += $edge->{info}->{size} || 0;
+                }
+            }
+                
+            print "$downloadSize\n";
+            
+            my $narSize = $info->{narSize} || 0;
+            print "$narSize\n";
         }
         
         else { die "unknown command `$cmd'"; }
@@ -79,6 +248,7 @@ elsif ($ARGV[0] ne "--substitute") {
 
 die unless scalar @ARGV == 2;
 my $targetPath = $ARGV[1];
+$fast = 0;
 
 
 # Create a temporary directory.
@@ -110,148 +280,9 @@ foreach my $localPath (@{$localPathList}) {
 }
 
 
-# Build a graph of all store paths that might contribute to the
-# construction of $targetPath, and the special node "start".  The
-# edges are either patch operations, or downloads of full NAR files.
-# The latter edges only occur between "start" and a store path.
-
-my %graph;
-
-$graph{"start"} = {d => 0, pred => undef, edges => []};
-
-my @queue = ();
-my $queueFront = 0;
-my %done;
-
-sub addToQueue {
-    my $v = shift;
-    return if defined $done{$v};
-    $done{$v} = 1;
-    push @queue, $v;
-}
-
-sub addNode {
-    my $u = shift;
-    $graph{$u} = {d => 999999999999, pred => undef, edges => []}
-        unless defined $graph{$u};
-}
-
-sub addEdge {
-    my $u = shift;
-    my $v = shift;
-    my $w = shift;
-    my $type = shift;
-    my $info = shift;
-    addNode $u;
-    push @{$graph{$u}->{edges}},
-        {weight => $w, start => $u, end => $v, type => $type, info => $info};
-    my $n = scalar @{$graph{$u}->{edges}};
-}
-
-addToQueue $targetPath;
-
-sub isValidPath {
-    my $p = shift;
-    return system("$binDir/nix-store --check-validity '$p' 2> /dev/null") == 0;
-}
-
-sub parseHash {
-    my $hash = shift;
-    if ($hash =~ /^(.+):(.+)$/) {
-        return ($1, $2);
-    } else {
-        return ("md5", $hash);
-    }
-}
-
-while ($queueFront < scalar @queue) {
-    my $u = $queue[$queueFront++];
-#    print "$u\n";
-
-    addNode $u;
-
-    # If the path already exists, it has distance 0 from the "start"
-    # node.
-    if (isValidPath($u)) {
-        addEdge "start", $u, 0, "present", undef;
-    }
-
-    else {
-
-        # Add patch edges.
-        my $patchList = $patches{$u};
-        foreach my $patch (@{$patchList}) {
-            if (isValidPath($patch->{basePath})) {
-                # !!! this should be cached
-                my ($baseHashAlgo, $baseHash) = parseHash $patch->{baseHash};
-                my $format = "--base32";
-                $format = "" if $baseHashAlgo eq "md5";
-                my $hash = `$binDir/nix-hash --type '$baseHashAlgo' $format "$patch->{basePath}"`;
-                chomp $hash;
-                if ($hash ne $baseHash) {
-                    print LOGFILE "$$ rejecting $patch->{basePath}\n";
-                    next;
-                }
-            }
-            addToQueue $patch->{basePath};
-            addEdge $patch->{basePath}, $u, $patch->{size}, "patch", $patch;
-        }
-
-        # Add NAR file edges to the start node.
-        my $narFileList = $narFiles{$u};
-        foreach my $narFile (@{$narFileList}) {
-            # !!! how to handle files whose size is not known in advance?
-            # For now, assume some arbitrary size (1 MB).
-            addEdge "start", $u, ($narFile->{size} || 1000000), "narfile", $narFile;
-            if ($u eq $targetPath) {
-                my $size = $narFile->{size} || -1;
-                print LOGFILE "$$ full-download-would-be $size\n";
-            }
-        }
-
-    }
-}
-
-
-# Run Dijkstra's shortest path algorithm to determine the shortest
-# sequence of download and/or patch actions that will produce
-# $targetPath.
-
-sub byDistance { # sort by distance, reversed
-    return -($graph{$a}->{d} <=> $graph{$b}->{d});
-}
-
-my @todo = keys %graph;
-
-while (scalar @todo > 0) {
-
-    # Remove the closest element from the todo list.
-    @todo = sort byDistance @todo;
-    my $u = pop @todo;
-
-    my $u_ = $graph{$u};
-
-    foreach my $edge (@{$u_->{edges}}) {
-        my $v_ = $graph{$edge->{end}};
-        if ($v_->{d} > $u_->{d} + $edge->{weight}) {
-            $v_->{d} = $u_->{d} + $edge->{weight};
-            # Store the edge; to edge->start is actually the
-            # predecessor.
-            $v_->{pred} = $edge; 
-        }
-    }
-}
-
-
-# Retrieve the shortest path from "start" to $targetPath.
-my @path = ();
-my $cur = $targetPath;
-die "don't know how to produce $targetPath\n"
-    unless defined $graph{$targetPath}->{pred};
-while ($cur ne "start") {
-    push @path, $graph{$cur}->{pred};
-    $cur = $graph{$cur}->{pred}->{start};
-}
+# Compute the shortest path.
+my @path = computeSmallestDownload $targetPath;
+die "don't know how to produce $targetPath\n" if scalar @path == 0;
 
 
 # Traverse the shortest path, perform the actions described by the
diff --git a/scripts/generate-patches.pl.in b/scripts/generate-patches.pl.in
deleted file mode 100755
index dba6473508d3..000000000000
--- a/scripts/generate-patches.pl.in
+++ /dev/null
@@ -1,416 +0,0 @@
-#! @perl@ -w -I@libexecdir@/nix
-
-use strict;
-use File::Temp qw(tempdir);
-use readmanifest;
-
-
-# Some patch generations options.
-
-# Max size of NAR archives to generate patches for.
-my $maxNarSize = $ENV{"NIX_MAX_NAR_SIZE"};
-$maxNarSize = 100 * 1024 * 1024 if !defined $maxNarSize;
-
-# If patch is bigger than this fraction of full archive, reject.
-my $maxPatchFraction = $ENV{"NIX_PATCH_FRACTION"};
-$maxPatchFraction = 0.60 if !defined $maxPatchFraction;
-
-
-die unless scalar @ARGV == 5;
-
-my $hashAlgo = "sha256";
-
-my $narDir = $ARGV[0];
-my $patchesDir = $ARGV[1];
-my $patchesURL = $ARGV[2];
-my $srcManifest = $ARGV[3];
-my $dstManifest = $ARGV[4];
-
-my $tmpDir = tempdir("nix-generate-patches.XXXXXX", CLEANUP => 1, TMPDIR => 1)
-    or die "cannot create a temporary directory";
-
-print "TEMP = $tmpDir\n";
-
-#END { rmdir $tmpDir; }
-
-my %srcNarFiles;
-my %srcLocalPaths;
-my %srcPatches;
-
-my %dstNarFiles;
-my %dstLocalPaths;
-my %dstPatches;
-
-readManifest "$srcManifest",
-    \%srcNarFiles, \%srcLocalPaths, \%srcPatches;
-
-readManifest "$dstManifest",
-    \%dstNarFiles, \%dstLocalPaths, \%dstPatches;
-
-
-sub findOutputPaths {
-    my $narFiles = shift;
-
-    my %outPaths;
-    
-    foreach my $p (keys %{$narFiles}) {
-
-        # Ignore derivations.
-        next if ($p =~ /\.drv$/);
-        
-        # Ignore builders (too much ambiguity -- they're all called
-        # `builder.sh').
-        next if ($p =~ /\.sh$/);
-        next if ($p =~ /\.patch$/);
-        
-        # Don't bother including tar files etc.
-        next if ($p =~ /\.tar$/ || $p =~ /\.tar\.(gz|bz2|Z|lzma|xz)$/ || $p =~ /\.zip$/ || $p =~ /\.bin$/ || $p =~ /\.tgz$/ || $p =~ /\.rpm$/ || $p =~ /cvs-export$/ || $p =~ /fetchhg$/);
-
-        $outPaths{$p} = 1;
-    }
-
-    return %outPaths;
-}
-
-print "finding src output paths...\n";
-my %srcOutPaths = findOutputPaths \%srcNarFiles;
-
-print "finding dst output paths...\n";
-my %dstOutPaths = findOutputPaths \%dstNarFiles;
-
-
-sub getNameVersion {
-    my $p = shift;
-    $p =~ /\/[0-9a-z]+((?:-[a-zA-Z][^\/-]*)+)([^\/]*)$/;
-    my $name = $1;
-    my $version = $2;
-    return undef unless defined $name && defined $version;
-    $name =~ s/^-//;
-    $version =~ s/^-//;
-    return ($name, $version);
-}
-
-
-# A quick hack to get a measure of the `distance' between two
-# versions: it's just the position of the first character that differs
-# (or 999 if they are the same).
-sub versionDiff {
-    my $s = shift;
-    my $t = shift;
-    my $i;
-    return 999 if $s eq $t;
-    for ($i = 0; $i < length $s; $i++) {
-        return $i if $i >= length $t or
-            substr($s, $i, 1) ne substr($t, $i, 1);
-    }
-    return $i;
-}
-
-
-sub getNarBz2 {
-    my $narFiles = shift;
-    my $storePath = shift;
-    
-    my $narFileList = $$narFiles{$storePath};
-    die "missing path $storePath" unless defined $narFileList;
-
-    my $narFile = @{$narFileList}[0];
-    die unless defined $narFile;
-
-    $narFile->{url} =~ /\/([^\/]+)$/;
-    die unless defined $1;
-    return "$narDir/$1";
-}
-
-
-sub containsPatch {
-    my $patches = shift;
-    my $storePath = shift;
-    my $basePath = shift;
-    my $patchList = $$patches{$storePath};
-    return 0 if !defined $patchList;
-    my $found = 0;
-    foreach my $patch (@{$patchList}) {
-        # !!! baseHash might differ
-        return 1 if $patch->{basePath} eq $basePath;
-    }
-    return 0;
-}
-
-
-# Compute the "weighted" number of uses of a path in the build graph.
-sub computeUses {
-    my $narFiles = shift;
-    my $path = shift;
-
-    # Find the deriver of $path.
-    return 1 unless defined $$narFiles{$path};
-    my $deriver = @{$$narFiles{$path}}[0]->{deriver};
-    return 1 unless defined $deriver && $deriver ne "";
-
-#    print "  DERIVER $deriver\n";
-
-    # Optimisation: build the referrers graph from the references
-    # graph.
-    my %referrers;
-    foreach my $q (keys %{$narFiles}) {
-        my @refs = split " ", @{$$narFiles{$q}}[0]->{references};
-        foreach my $r (@refs) {
-            $referrers{$r} = [] unless defined $referrers{$r};
-            push @{$referrers{$r}}, $q;
-        }
-    }
-
-    # Determine the shortest path from $deriver to all other reachable
-    # paths in the `referrers' graph.
-
-    my %dist;
-    $dist{$deriver} = 0;
-
-    my @queue = ($deriver);
-    my $pos = 0;
-    
-    while ($pos < scalar @queue) {
-        my $p = $queue[$pos];
-        $pos++;
-
-        foreach my $q (@{$referrers{$p}}) {
-            if (!defined $dist{$q}) {
-                $dist{$q} = $dist{$p} + 1;
-#                print "    $q $dist{$q}\n";
-                push @queue, $q;
-            }
-        }
-    }
-
-    my $wuse = 1.0;
-    foreach my $user (keys %dist) {
-        next if $user eq $deriver;
-#        print "    $user $dist{$user}\n";
-        $wuse += 1.0 / 2.0**$dist{$user};
-    }
-
-#    print "    XXX $path $wuse\n";
-    
-    return $wuse;
-}
-
-
-# For each output path in the destination, see if we need to / can
-# create a patch.
-
-print "creating patches...\n";
-
-foreach my $p (keys %dstOutPaths) {
-
-    # If exactly the same path already exists in the source, skip it.
-    next if defined $srcOutPaths{$p};
-    
-    print "  $p\n";
-
-    # If not, then we should find the paths in the source that are
-    # `most' likely to be present on a system that wants to install
-    # this path.
-
-    (my $name, my $version) = getNameVersion $p;
-    next unless defined $name && defined $version;
-
-    my @closest = ();
-    my $closestVersion;
-    my $minDist = -1; # actually, larger means closer
-
-    # Find all source paths with the same name.
-
-    foreach my $q (keys %srcOutPaths) {
-        (my $name2, my $version2) = getNameVersion $q;
-	next unless defined $name2 && defined $version2;
-
-        if ($name eq $name2) {
-
-            # If the sizes differ too much, then skip.  This
-            # disambiguates between, e.g., a real component and a
-            # wrapper component (cf. Firefox in Nixpkgs).
-            my $srcSize = @{$srcNarFiles{$q}}[0]->{size};
-            my $dstSize = @{$dstNarFiles{$p}}[0]->{size};
-            my $ratio = $srcSize / $dstSize;
-            $ratio = 1 / $ratio if $ratio < 1;
-#            print "  SIZE $srcSize $dstSize $ratio $q\n";
-
-            if ($ratio >= 3) {
-                print "  SKIPPING $q due to size ratio $ratio ($srcSize $dstSize)\n";
-                next;
-            }
-
-            # If the numbers of weighted uses differ too much, then
-            # skip.  This disambiguates between, e.g., the bootstrap
-            # GCC and the final GCC in Nixpkgs.
-#            my $srcUses = computeUses \%srcNarFiles, $q;
-#            my $dstUses = computeUses \%dstNarFiles, $p;
-#            $ratio = $srcUses / $dstUses;
-#            $ratio = 1 / $ratio if $ratio < 1;
-#            print "  USE $srcUses $dstUses $ratio $q\n";
-            
-#            if ($ratio >= 2) {
-#                print "  SKIPPING $q due to use ratio $ratio ($srcUses $dstUses)\n";
-#                next;
-#            }
-
-            # If there are multiple matching names, include the ones
-            # with the closest version numbers.
-            my $dist = versionDiff $version, $version2;
-            if ($dist > $minDist) {
-                $minDist = $dist;
-                @closest = ($q);
-                $closestVersion = $version2;
-            } elsif ($dist == $minDist) {
-                push @closest, $q;
-            }
-        }
-    }
-
-    if (scalar(@closest) == 0) {
-        print "  NO BASE: $p\n";
-        next;
-    }
-
-    foreach my $closest (@closest) {
-
-        # Generate a patch between $closest and $p.
-        print "  $p <- $closest\n";
-
-        # If the patch already exists, skip it.
-        if (containsPatch(\%srcPatches, $p, $closest) ||
-            containsPatch(\%dstPatches, $p, $closest))
-        {
-            print "    skipping, already exists\n";
-            next;
-        }
-
-#        next;
-        
-        my $srcNarBz2 = getNarBz2 \%srcNarFiles, $closest;
-        my $dstNarBz2 = getNarBz2 \%dstNarFiles, $p;
-
-        if (! -f $srcNarBz2) {
-            warn "patch source archive $srcNarBz2 is missing\n";
-            next;
-        }
-
-        system("@bunzip2@ < $srcNarBz2 > $tmpDir/A") == 0
-            or die "cannot unpack $srcNarBz2";
-
-        if ((stat "$tmpDir/A")[7] >= $maxNarSize) {
-            print "    skipping, source is too large\n";
-            next;
-        }
-        
-        system("@bunzip2@ < $dstNarBz2 > $tmpDir/B") == 0
-            or die "cannot unpack $dstNarBz2";
-
-        if ((stat "$tmpDir/B")[7] >= $maxNarSize) {
-            print "    skipping, destination is too large\n";
-            next;
-        }
-        
-        system("@libexecdir@/bsdiff $tmpDir/A $tmpDir/B $tmpDir/DIFF") == 0
-            or die "cannot compute binary diff";
-
-        my $baseHash = `@bindir@/nix-hash --flat --type $hashAlgo --base32 $tmpDir/A` or die;
-        chomp $baseHash;
-
-        my $narHash = `@bindir@/nix-hash --flat --type $hashAlgo --base32 $tmpDir/B` or die;
-        chomp $narHash;
-
-        my $narDiffHash = `@bindir@/nix-hash --flat --type $hashAlgo --base32 $tmpDir/DIFF` or die;
-        chomp $narDiffHash;
-
-        my $narDiffSize = (stat "$tmpDir/DIFF")[7];
-        my $dstNarBz2Size = (stat $dstNarBz2)[7];
-
-        print "    size $narDiffSize; full size $dstNarBz2Size\n";
-        
-        if ($narDiffSize >= $dstNarBz2Size) {
-            print "    rejecting; patch bigger than full archive\n";
-            next;
-        }
-    
-        if ($narDiffSize / $dstNarBz2Size >= $maxPatchFraction) {
-            print "    rejecting; patch too large relative to full archive\n";
-            next;
-        }
-    
-        my $finalName =
-            "$narDiffHash.nar-bsdiff";
-
-        if (-e "$patchesDir/$finalName") {
-            print "    not copying, already exists\n";
-        }
-
-        else {
-
-            system("cp '$tmpDir/DIFF' '$patchesDir/$finalName.tmp'") == 0
-                or die "cannot copy diff";
-            
-            rename("$patchesDir/$finalName.tmp", "$patchesDir/$finalName")
-                or die "cannot rename $patchesDir/$finalName.tmp";
-            
-        }
-        
-        # Add the patch to the manifest.
-        addPatch \%dstPatches, $p,
-            { url => "$patchesURL/$finalName", hash => "$hashAlgo:$narDiffHash"
-            , size => $narDiffSize, basePath => $closest, baseHash => "$hashAlgo:$baseHash"
-            , narHash => "$hashAlgo:$narHash", patchType => "nar-bsdiff"
-            }, 0;
-    }
-}
-
-
-# Add in any potentially useful patches in the source (namely, those
-# patches that produce either paths in the destination or paths that
-# can be used as the base for other useful patches).
-
-print "propagating patches...\n";
-
-my $changed;
-do {
-    # !!! we repeat this to reach the transitive closure; inefficient
-    $changed = 0;
-
-    print "loop\n";
-
-    my %dstBasePaths;
-    foreach my $q (keys %dstPatches) {
-	foreach my $patch (@{$dstPatches{$q}}) {
-	    $dstBasePaths{$patch->{basePath}} = 1;
-	}
-    }
-
-    foreach my $p (keys %srcPatches) {
-        my $patchList = $srcPatches{$p};
-
-        my $include = 0;
-
-        # Is path $p included in the destination?  If so, include
-        # patches that produce it.
-        $include = 1 if defined $dstNarFiles{$p};
-
-        # Is path $p a path that serves as a base for paths in the
-        # destination?  If so, include patches that produce it.
-	# !!! check baseHash
-        $include = 1 if defined $dstBasePaths{$p};
-
-        if ($include) {
-            foreach my $patch (@{$patchList}) {
-                $changed = 1 if addPatch \%dstPatches, $p, $patch;
-            }
-        }
-        
-    }
-    
-} while $changed;
-
-
-# Rewrite the manifest of the destination (with the new patches).
-writeManifest "${dstManifest}",
-    \%dstNarFiles, \%dstPatches;
diff --git a/scripts/nix-build.in b/scripts/nix-build.in
index ed85d5712128..f9d81b36c7a0 100644
--- a/scripts/nix-build.in
+++ b/scripts/nix-build.in
@@ -123,6 +123,11 @@ EOF
         $verbose = 1;
     }
     
+    elsif ($arg eq "--quiet") {
+        push @buildArgs, $arg;
+        push @instArgs, $arg;
+    }
+    
     elsif (substr($arg, 0, 1) eq "-") {
         push @buildArgs, $arg;
     }
@@ -165,7 +170,7 @@ foreach my $expr (@exprs) {
 
     # Build.
     my @outPaths;
-    $pid = open(OUTPATHS, "-|") || exec "$binDir/nix-store", "--add-root", $outLink, "--indirect", "-rv",
+    $pid = open(OUTPATHS, "-|") || exec "$binDir/nix-store", "--add-root", $outLink, "--indirect", "-r",
         @buildArgs, @drvPaths;
     while (<OUTPATHS>) {chomp; push @outPaths, $_;}
     if (!close OUTPATHS) {
diff --git a/scripts/nix-copy-closure.in b/scripts/nix-copy-closure.in
index a477cc01a4cf..c037f003f0d0 100644
--- a/scripts/nix-copy-closure.in
+++ b/scripts/nix-copy-closure.in
@@ -1,6 +1,6 @@
 #! @perl@ -w -I@libexecdir@/nix
 
-use ssh;
+use SSH;
 
 my $binDir = $ENV{"NIX_BIN_DIR"} || "@bindir@";
 
@@ -61,7 +61,7 @@ if ($toMode) { # Copy TO the remote machine.
     my @allStorePaths;
 
     # Get the closure of this path.
-    my $pid = open(READ, "$binDir/nix-store --query --requisites @storePaths|") or die;
+    my $pid = open(READ, "set -f; $binDir/nix-store --query --requisites @storePaths|") or die;
     
     while (<READ>) {
         chomp;
@@ -73,7 +73,7 @@ if ($toMode) { # Copy TO the remote machine.
 
 
     # Ask the remote host which paths are invalid.
-    open(READ, "ssh $sshHost @sshOpts nix-store --check-validity --print-invalid @allStorePaths|");
+    open(READ, "set -f; ssh $sshHost @sshOpts nix-store --check-validity --print-invalid @allStorePaths|");
     my @missing = ();
     while (<READ>) {
         chomp;
@@ -88,7 +88,7 @@ if ($toMode) { # Copy TO the remote machine.
         print STDERR "  $_\n" foreach @missing;
         my $extraOpts = "";
         $extraOpts .= "--sign" if $sign == 1;
-        system("nix-store --export $extraOpts @missing $compressor | ssh $sshHost @sshOpts '$decompressor nix-store --import'") == 0
+        system("set -f; nix-store --export $extraOpts @missing $compressor | ssh $sshHost @sshOpts '$decompressor nix-store --import'") == 0
             or die "copying store paths to remote machine `$sshHost' failed: $?";
     }
 
@@ -101,7 +101,7 @@ else { # Copy FROM the remote machine.
     # machine.  Paths are assumed to be store paths; there is no
     # resolution (following of symlinks).
     my $pid = open(READ,
-        "ssh @sshOpts $sshHost nix-store --query --requisites @storePaths|") or die;
+        "set -f; ssh @sshOpts $sshHost nix-store --query --requisites @storePaths|") or die;
     
     my @allStorePaths;
 
@@ -115,7 +115,7 @@ else { # Copy FROM the remote machine.
 
 
     # What paths are already valid locally?
-    open(READ, "@bindir@/nix-store --check-validity --print-invalid @allStorePaths|");
+    open(READ, "set -f; @bindir@/nix-store --check-validity --print-invalid @allStorePaths|");
     my @missing = ();
     while (<READ>) {
         chomp;
@@ -130,7 +130,7 @@ else { # Copy FROM the remote machine.
         print STDERR "  $_\n" foreach @missing;
         my $extraOpts = "";
         $extraOpts .= "--sign" if $sign == 1;
-        system("ssh $sshHost @sshOpts 'nix-store --export $extraOpts @missing $compressor' | $decompressor @bindir@/nix-store --import") == 0
+        system("set -f; ssh $sshHost @sshOpts 'nix-store --export $extraOpts @missing $compressor' | $decompressor @bindir@/nix-store --import") == 0
             or die "copying store paths from remote machine `$sshHost' failed: $?";
     }
 
diff --git a/scripts/nix-generate-patches.in b/scripts/nix-generate-patches.in
new file mode 100644
index 000000000000..c96cc704a1e8
--- /dev/null
+++ b/scripts/nix-generate-patches.in
@@ -0,0 +1,42 @@
+#! @perl@ -w -I@libexecdir@/nix
+
+use strict;
+use File::Temp qw(tempdir);
+use NixManifest;
+use GeneratePatches;
+
+if (scalar @ARGV != 5) {
+    print STDERR <<EOF;
+Usage: nix-generate-patches NAR-DIR PATCH-DIR PATCH-URI OLD-MANIFEST NEW-MANIFEST
+
+This command generates binary patches between NAR files listed in
+OLD-MANIFEST and NEW-MANIFEST.  The patches are written to the
+directory PATCH-DIR, and the prefix PATCH-URI is used to generate URIs
+for the patches.  The patches are added to NEW-MANIFEST.  All NARs are
+required to exist in NAR-DIR.  Patches are generated between
+succeeding versions of packages with the same name.
+EOF
+    exit 1;
+}
+
+my $narPath = $ARGV[0];
+my $patchesPath = $ARGV[1];
+my $patchesURL = $ARGV[2];
+my $srcManifest = $ARGV[3];
+my $dstManifest = $ARGV[4];
+
+my (%srcNarFiles, %srcLocalPaths, %srcPatches);
+readManifest $srcManifest, \%srcNarFiles, \%srcLocalPaths, \%srcPatches;
+
+my (%dstNarFiles, %dstLocalPaths, %dstPatches);
+readManifest $dstManifest, \%dstNarFiles, \%dstLocalPaths, \%dstPatches;
+
+my $tmpDir = tempdir("nix-generate-patches.XXXXXX", CLEANUP => 1, TMPDIR => 1)
+    or die "cannot create a temporary directory";
+
+generatePatches \%srcNarFiles, \%dstNarFiles, \%srcPatches, \%dstPatches,
+    $narPath, $patchesPath, $patchesURL, $tmpDir;
+
+propagatePatches \%srcPatches, \%dstNarFiles, \%dstPatches;
+
+writeManifest $dstManifest, \%dstNarFiles, \%dstPatches;
diff --git a/scripts/nix-pull.in b/scripts/nix-pull.in
index e2a0cc1fafdf..f3b533ff7a4c 100644
--- a/scripts/nix-pull.in
+++ b/scripts/nix-pull.in
@@ -2,7 +2,7 @@
 
 use strict;
 use File::Temp qw(tempdir);
-use readmanifest;
+use NixManifest;
 
 my $tmpDir = tempdir("nix-pull.XXXXXX", CLEANUP => 1, TMPDIR => 1)
     or die "cannot create a temporary directory";
diff --git a/scripts/nix-push.in b/scripts/nix-push.in
index 38097f740162..1d8ba86a8d0c 100644
--- a/scripts/nix-push.in
+++ b/scripts/nix-push.in
@@ -2,7 +2,7 @@
 
 use strict;
 use File::Temp qw(tempdir);
-use readmanifest;
+use NixManifest;
 
 my $hashAlgo = "sha256";
 
@@ -172,12 +172,6 @@ for (my $n = 0; $n < scalar @storePaths; $n++) {
     $narbz2Hash =~ /^[0-9a-z]+$/ or die "invalid hash";
     close HASH;
 
-    open HASH, "$narDir/nar-hash" or die "cannot open nar-hash";
-    my $narHash = <HASH>;
-    chomp $narHash;
-    $narHash =~ /^[0-9a-z]+$/ or die "invalid hash";
-    close HASH;
-    
     my $narName = "$narbz2Hash.nar.bz2";
 
     my $narFile = "$narDir/$narName";
@@ -195,6 +189,14 @@ for (my $n = 0; $n < scalar @storePaths; $n++) {
     chomp $deriver;
     $deriver = "" if $deriver eq "unknown-deriver";
 
+    my $narHash = `$binDir/nix-store --query --hash '$storePath'`;
+    die "cannot query hash for `$storePath'" if $? != 0;
+    chomp $narHash;
+
+    my $narSize = `$binDir/nix-store --query --size '$storePath'`;
+    die "cannot query size for `$storePath'" if $? != 0;
+    chomp $narSize;
+
     my $url;
     if ($localCopy) {
         $url = "$targetArchivesUrl/$narName";
@@ -205,7 +207,8 @@ for (my $n = 0; $n < scalar @storePaths; $n++) {
         { url => $url
         , hash => "$hashAlgo:$narbz2Hash"
         , size => $narbz2Size
-        , narHash => "$hashAlgo:$narHash"
+        , narHash => "$narHash"
+        , narSize => $narSize
         , references => $references
         , deriver => $deriver
         }