diff --git a/web/clitools/mustool.php b/web/clitools/mustool.php
index 2c303f6..04c9021 100755
--- a/web/clitools/mustool.php
+++ b/web/clitools/mustool.php
@@ -21,6 +21,7 @@ require(__DIR__.'/lib/delinstbyid.php');
 $levs=['Debug', 'Info', 'Warning', 'Error'];
 
 $opts=array(
+	'revive'=>false,
 	'shuffle'=>false,
 	'updstats'=>false,
 	'clean'=>false,
@@ -41,6 +42,9 @@ $help='mustool.php
    you choose whether you want to delete them and all records referencing them
    in other tables.
    Example: mustool.php deleteinstswhere "IsMastodon!=1"
+  revive
+   Set a new, succesful check with current time for every instance that
+   succesfully responded to last check.
   shuffle
    Randomize instances list (values in «RPos» column).
   updstats
@@ -74,6 +78,9 @@ for ($i=1; $i<$argc; $i++) {
 	} elseif ($argv[$i]=='shuffle') {
 		$dosome=true;
 		$opts['shuffle']=true;
+	} elseif ($argv[$i]=='revive') {
+		$dosome=true;
+		$opts['revive']=true;
 	} elseif ($argv[$i]=='updstats') {
 		$dosome=true;
 		$opts['updstats']=true;
@@ -109,7 +116,7 @@ if ($opts['deleteinstswhere']) {
 	$buf=[];
 	while ($row=mysqli_fetch_assoc($res)) $buf[]=$row;
 	$cbuf=count($buf);
-	if ($cbuf) {
+	if ($cbuf>0) {
 		foreach ($buf as $row) echo($row['URI'].' (ID='.$row['ID'].')'.N);
 		echo('Do you really want to delete those '.$cbuf.' record(s)? Enter «YES» to do it, anything else to not do it: ');
 		$inp=rtrim(fgets(STDIN));
@@ -123,10 +130,33 @@ if ($opts['deleteinstswhere']) {
 			}
 		}
 	} else {
-		eecho('no Instances records match expression «'.$opts['deleteinstswhereconds'].'».'.N);
+		eecho('no Instances records match expression «'.$opts['deleteinstswhereconds'].'».'.N,2);
 	}
 }
 
+if ($opts['revive']) {
+	$now=time();
+	$res=myq($link,'SELECT * FROM Instances WHERE WasLastCheckOk IS TRUE;');
+	$buf=[];
+	while ($row=mysqli_fetch_assoc($res)) $buf[]=$row;
+	$cbuf=count($buf);
+	$i=0;
+	foreach ($buf as $row) {
+		$i++;
+		$res=myq($link,'INSERT INTO InstChecks (InstID, Time, Status) VALUES ('.$row['ID'].', '.$now.', 1);');
+		if ($res!==false) {
+			$res=myq($link,'UPDATE Instances SET TotChecks='.($row['TotChecks']+1).', OkChecks='.($row['OkChecks']+1).', WasLastCheckOk=1, LastOkCheckTS='.$now.' WHERE ID='.$row['ID'].';');
+			if ($res===false)
+				mexit('could not update instance record with ID='.$row['ID'].'; shutting down.'.N,3);
+			else
+				eecho("{$i}/{$cbuf}\n",1);
+		} else {
+			mexit('could not insert new check record into InstChecks for instance with ID='.$row['ID'].'; shutting down.'.N,3);
+		}
+	}
+	eecho('done! Affected rows: '.$cbuf.'.'.N,1);
+}
+
 if ($opts['shuffle']) {
 	eecho('randomizing values in «RPos» column...'.N,1);
 	$res=myq($link,'SELECT ID FROM Instances');
@@ -239,7 +269,7 @@ if ($opts['clean']) {
 }
 
 if ($opts['optimize']) {
-	eecho('optimizing all the tables in the database...'.N);
+	eecho('optimizing all the tables in the database...'.N,1);
 	$res=myq($link,'SHOW TABLES');
 	while ($row=mysqli_fetch_row($res)) {
 		$rres=myq($link,'OPTIMIZE TABLE '.$row[0]);