MRTG提示错误

flyibm

有一台MRTG服务器，邮件信息如下：

From root@localhost.localdomain  Sun Oct 21 22:00:01 2012
Date: Sun, 21 Oct 2012 22:00:01 +0800
From: root@localhost.localdomain (Cron Daemon)
To: root@localhost.localdomain
Subject: Cron <root@localhost> env LANG=C /usr/bin/mrtg /var/www/html/mrtg/mrtg.cfg
Content-Type: text/plain; charset=UTF-8
Auto-Submitted: auto-generated
X-Cron-Env: <SHELL=/bin/sh>
X-Cron-Env: <HOME=/root>
X-Cron-Env: <PATH=/usr/bin:/bin>
X-Cron-Env: <LOGNAME=root>
X-Cron-Env: <USER=root>

Sunday, 21 October 2012 at 22:00: ERROR: I guess another mrtg is running. A lockfile (/var/www/html/mrtg/mrtg.cfg_l) aged
180 seconds is hanging around. If you are sure that no other mrtg
is running you can remove the lockfile

请问是什么原因？应该怎么解决？谢谢。