diff --git a/src/lib/Hydra/Controller/Build.pm b/src/lib/Hydra/Controller/Build.pm
index 64919f6b..c40e2fa0 100644
--- a/src/lib/Hydra/Controller/Build.pm
+++ b/src/lib/Hydra/Controller/Build.pm
@@ -214,9 +214,7 @@ sub cancel : Chained('build') PathPart Args(0) {
         # builds as well, but we would have to send a signal or
         # something to the build process.
 
-        $build->finished(1);
-        $build->timestamp(time());
-        $build->update;
+        $build->update({finished => 1, timestamp => time});
 
         $c->model('DB::BuildResultInfo')->create(
             { id => $build->id
@@ -233,4 +231,24 @@ sub cancel : Chained('build') PathPart Args(0) {
 }
 
 
+sub keep : Chained('build') PathPart Args(1) {
+    my ($self, $c, $newStatus) = @_;
+
+    my $build = $c->stash->{build};
+
+    requireProjectOwner($c, $build->project);
+
+    die unless $newStatus == 0 || $newStatus == 1;
+
+    $c->model('DB')->schema->txn_do(sub {
+        $build->resultInfo->update({keep => int $newStatus});
+    });
+
+    $c->flash->{buildMsg} =
+        $newStatus == 0 ? "Build will not be kept." : "Build will be kept.";
+    
+    $c->res->redirect($c->uri_for($self->action_for("view_build"), $c->req->captures));
+}
+
+
 1;
diff --git a/src/root/build.tt b/src/root/build.tt
index 486893a7..8b5b6e9e 100644
--- a/src/root/build.tt
+++ b/src/root/build.tt
@@ -57,7 +57,7 @@
           <span class="error">Build failed</span>
           (see <a href="#nix-error">below</a>)
         [% END %]
-        [% IF build.resultInfo.buildstatus == 3 || build.resultInfo.buildstatus == 4 %]
+        [% IF c.user_exists && (build.resultInfo.buildstatus == 3 || build.resultInfo.buildstatus == 4) %]
           <form action="[% c.uri_for('/build' build.id 'restart') %]" method="post" class="inline">
             <button id="restart" type="submit">Restart</button>
           </form>
@@ -174,6 +174,30 @@
       <td>[% build.schedulingInfo.priority %]</td>
     </tr>
   [% END %]
+  [% IF build.finished && build.buildproducts %]
+    <tr>
+      <th>Availability:</th>
+      <td>
+        [% IF !available %]
+          <em>Build output is no longer available</em>
+        [% ELSIF build.resultInfo.keep %]
+          <em>Build output will be kept permanently</em>
+          [% IF c.user_exists %]
+            <form action="[% c.uri_for('/build' build.id 'keep' 0) %]" method="post" class="inline">
+              <button id="unkeep" type="submit">Unkeep</button>
+            </form>
+          [% END %]
+        [% ELSE %]
+          <em>Build output is available, but may be garbage-collected</em>
+          [% IF c.user_exists %]
+            <form action="[% c.uri_for('/build' build.id 'keep' 1) %]" method="post" class="inline">
+              <button id="keep" type="submit">Keep</button>
+            </form>
+          [% END %]
+        [% END %]
+      </td>
+    </tr>
+  [% END %]
 </table>
 
 
diff --git a/src/script/hydra_update_gc_roots.pl b/src/script/hydra_update_gc_roots.pl
index 2949a0c9..ca581e88 100755
--- a/src/script/hydra_update_gc_roots.pl
+++ b/src/script/hydra_update_gc_roots.pl
@@ -21,7 +21,7 @@ sub registerRoot {
 
 sub keepBuild {
     my ($build) = @_;
-    print "keeping build ", $build->id, " (",
+    print STDERR "keeping build ", $build->id, " (",
             strftime("%Y-%m-%d %H:%M:%S", localtime($build->timestamp)), ")\n";
     if (isValidPath($build->outpath)) {
         registerRoot $build->outpath;
@@ -37,16 +37,16 @@ foreach my $project ($db->resultset('Projects')->all) {
 
     # Go over all jobs in this project.
 
-    foreach my $job ($project->builds->search({},
-        {select => [{distinct => 'job'}], as => ['job']}))
-    {
-        print "*** looking for builds to keep in job ", $project->name, ":", $job->job, "\n";
+    foreach my $job ($project->jobs->all) {
+        print STDERR "*** looking for builds to keep in job ",
+            $project->name, ":", $job->jobset->name, ":", $job->name, "\n";
 
         # Keep the N most recent successful builds for each job and
         # platform.
-        my @recentBuilds = $project->builds->search(
-            { job => $job->job
-            , finished => 1
+        # !!! Take time into account? E.g. don't delete builds that
+        # are younger than N days.
+        my @recentBuilds = $job->builds->search(
+            { finished => 1
             , buildStatus => 0 # == success
             },
             { join => 'resultInfo'
@@ -55,13 +55,12 @@ foreach my $project ($db->resultset('Projects')->all) {
             });
         
         keepBuild $_ foreach @recentBuilds;
-
     }
 
     # Go over all releases in this project.
 
     foreach my $releaseSet ($project->releasesets->all) {
-        print "*** looking for builds to keep in release set ", $project->name, ":", $releaseSet->name, "\n";
+        print STDERR "*** looking for builds to keep in release set ", $project->name, ":", $releaseSet->name, "\n";
 
         (my $primaryJob) = $releaseSet->releasesetjobs->search({isprimary => 1});
         my $jobs = [$releaseSet->releasesetjobs->all];
@@ -69,7 +68,7 @@ foreach my $project ($db->resultset('Projects')->all) {
         # Keep all builds belonging to the most recent successful release.
         my $latest = getLatestSuccessfulRelease($project, $primaryJob, $jobs);
         if (defined $latest) {
-            print "keeping latest successful release ", $latest->id, " (", $latest->get_column('releasename'), ")\n";
+            print STDERR "keeping latest successful release ", $latest->id, " (", $latest->get_column('releasename'), ")\n";
             my $release = getRelease($latest, $jobs);
             keepBuild $_->{build} foreach @{$release->{jobs}};
         }
@@ -79,16 +78,16 @@ foreach my $project ($db->resultset('Projects')->all) {
 
 
 # Keep all builds that have been marked as "keep".
-print "*** looking for kept builds\n";
+print STDERR "*** looking for kept builds\n";
 my @buildsToKeep = $db->resultset('Builds')->search({finished => 1, keep => 1}, {join => 'resultInfo'});
 keepBuild $_ foreach @buildsToKeep;
 
 
 # For scheduled builds, we register the derivation and the output as a GC root.
-print "*** looking for scheduled builds\n";
+print STDERR "*** looking for scheduled builds\n";
 foreach my $build ($db->resultset('Builds')->search({finished => 0}, {join => 'schedulingInfo'})) {
     if (isValidPath($build->drvpath)) {
-        print "keeping scheduled build ", $build->id, " (",
+        print STDERR "keeping scheduled build ", $build->id, " (",
             strftime("%Y-%m-%d %H:%M:%S", localtime($build->timestamp)), ")\n";
         registerRoot $build->drvpath;
         registerRoot $build->outpath;
@@ -99,7 +98,7 @@ foreach my $build ($db->resultset('Builds')->search({finished => 0}, {join => 's
 
 
 # Remove existing roots that are no longer wanted.  !!! racy
-print "*** removing unneeded GC roots\n";
+print STDERR "*** removing unneeded GC roots\n";
 
 my $gcRootsDir = getGCRootsDir;