         cb         : undefined
 
     dbg = (m) -> winston.debug("rollback_to_snapshot(#{opts.project_id},#{opts.host},#{opts.snapshot}): #{m}")
-    snapshot = opts.snapshot
+    snapshot_name = opts.snapshot
     f = filesystem(opts.project_id)
 
     async.series([
         (cb) ->
-            if snapshot?
-                if snapshot.indexOf('@') == -1
-                    snapshot = opts.project_id + "@" + snapshot
+            if snapshot_name?
+                if snapshot_name.indexOf('@') == -1
+                    snapshot_name = opts.project_id + "@" + snapshot_name
                 cb()
             else
                 dbg("get most recent snapshot name")

                        if err
                            cb(err)
                        else
                            snapshot = output.stdout.trim()
                            cb()
        (cb) ->
            dbg("rollback to #{snapshot}")
            execute_on
                host    : opts.host
                command : "sudo zfs rollback #{snapshot}"
                timeout : 300
                cb      : cb
    ], (err) -> opts.cb?(err))

        host       : undefined  # defaults to current host, if deployed
        unset_loc  : false      # set location to undefined in the database
        umount     : false      # don't use this -- it causes ZFS deadlock, which requires machine reboots.  Horrible and not needed.
        wait_for_replicate : false  # if true, waits for post-snapshot replication to complete
        cb         : required

    if not opts.host?
