Index: locker/bin/signup-sql
===================================================================
--- locker/bin/signup-sql	(revision 660)
+++ locker/bin/signup-sql	(revision 663)
@@ -53,7 +53,13 @@
     echo you control.  Please enter the name of the selected locker below.
     echo "(For the locker /mit/sipb, you would enter sipb)."
-    printf "Locker name: "
-    read lname
-    lroot="/mit/$lname" 
+    while true; do
+        printf "Locker name: "
+        read lname
+        if attach "$lname"; then
+            break
+        fi
+        echo "$lname is not a valid locker name."
+    done
+    lroot="/mit/$lname"
 else
     echo