diff --git a/classes/clean.php b/classes/clean.php
index d6fc2b1..a927c59 100644
--- a/classes/clean.php
+++ b/classes/clean.php
@@ -398,4 +398,43 @@ protected static function execute_sql($sql) {
     public static function get_settings_section_url($sectionname) {
         return new \moodle_url('/admin/settings.php', array('section' => $sectionname));
     }
+
+    /**
+     * Log some context of where and why this was run.
+     */
+    public static function debug_info() {
+        global $CFG;
+
+        $context = "Time: " . \userdate(time()) . "\n";
+        $context .= "TZ:   " . $CFG->timezone . "\n";
+        $context .= "Host: " . gethostname() . "\n";
+        $context .= "Moodle User: " . $USER->username . "\n";
+        $context .= "\$CFG->dbhost: " . $CFG->dbhost . "\n";
+        $context .= "\$CFG->dbuser: " . $CFG->dbuser . "\n";
+        $context .= "\$CFG->dataroot: " . $CFG->dataroot . "\n";
+        $context .= "\$CFG->wwwroot: " . $CFG->wwwroot . "\n";
+        $context .= "\$CFG->original_wwwroot: " . $CFG->original_wwwroot . "\n";
+
+        self::log($context);
+
+        // Also set this in the DB.
+        set_config('lastwash', $context, 'local_datacleaner');
+
+    }
+
+    /**
+     * Log details in a variety of places
+     *
+     * @param string
+     */
+    public static function log($string) {
+        global $CFG;
+
+        // Send it to stderr.
+        error_log($string);
+
+        // Stash a copy into sitedir log file.
+        mkdir("$CFG->dataroot/datacleaner");
+        file_put_contents("$CFG->dataroot/datacleaner/clean.log", $string, FILE_APPEND);
+    }
 }
diff --git a/cli/clean.php b/cli/clean.php
index 12feba9..c2abd9f 100644
--- a/cli/clean.php
+++ b/cli/clean.php
@@ -26,6 +26,8 @@
 require_once($CFG->libdir.'/adminlib.php');
 require_once(dirname(__FILE__) . '/lib.php');
 
+use local_datacleaner\clean;
+
 // Now get cli options.
 list($options, $unrecognized) = cli_get_params(
     array(
@@ -102,16 +104,18 @@
 }
 
 if ($options['dryrun']) {
-    echo "=== DRY RUN ===\n";
+    clean::log("=== DRY RUN ===\n");
 }
 
 $filter = $options['filter'];
 if ($filter) {
-    echo "Filtering to ONLY run: $filter \n";
+    clean::log("Filtering to ONLY run: $filter \n");
 }
 
 $cascade = null;
 
+local_datacleaner\clean::debug_info();
+
 foreach ($plugins as $plugin) {
     // Get the class that does the work.
     $classname = 'cleaner_' . $plugin->name . '\clean';
@@ -127,7 +131,7 @@
     // Skip subplugins that have a sort order that is greater or equal to 200.
     if ($options['run-pre-wash']) {
         if ($plugin->sortorder >= 200) {
-            echo "NOTICE: Pre washing only. Skipping {$plugin->name} ({$plugin->sortorder}) cleaner.\n";
+            clean::log("NOTICE: Pre washing only. Skipping {$plugin->name} ({$plugin->sortorder}) cleaner.\n");
             continue;
         }
     }
@@ -136,18 +140,18 @@
     // Skip subplugins that have a sort order that is less than 200.
     if ($options['run-post-wash']) {
         if ($plugin->sortorder < 200) {
-            echo "NOTICE: Post washing only. Skipping {$plugin->name} ({$plugin->sortorder}) cleaner.\n";
+            clean::log("NOTICE: Post washing only. Skipping {$plugin->name} ({$plugin->sortorder}) cleaner.\n");
             continue;
         }
     }
 
-    echo "== Running {$plugin->name} cleaner ==\n";
     if (!class_exists($classname)) {
-        echo "ERROR: Unable to locate local/datacleaner/cleaner/{$plugin->name}/classes/clean.php class. Skipping.\n";
+        clean::log("ERROR: Unable to locate local/datacleaner/cleaner/{$plugin->name}/classes/clean.php class. Skipping.\n");
         continue;
     }
 
     $class = new $classname($options);
+    clean::log("== Running {$plugin->name} cleaner ==\n");
 
     if (is_null($cascade) && $class->needs_cascade_delete()) {
         $cascade = new \local_datacleaner\schema_add_cascade_delete($options);
@@ -160,4 +164,4 @@
     $class->execute();
 }
 
-echo "Done.\n";
+clean::log("Done.\n");
diff --git a/cli/lib.php b/cli/lib.php
index 45b5044..7d2614c 100644
--- a/cli/lib.php
+++ b/cli/lib.php
@@ -23,6 +23,8 @@
 
 defined('MOODLE_INTERNAL') || die();
 
+use local_datacleaner\clean;
+
 /**
  * Print a message to the terminal.
  *
@@ -38,6 +40,7 @@ function print_message($text, $highlight = false) {
     } else {
         echo $text;
     }
+    clean::log($text);
 }
 
 /**