hadoopmaster主机上传文件出错：

hadoopmaster主机上传文件出错： put: File /a.txt._COPYING_ could only be replicated to 0 nodes instead of minReplication (=1). There are 3 datanode(s) running and 3 node(s) are excluded in this operation.

刚开始装好hadoop的时候，namenode机上传文件没有错误，今天打开时突然不能上传文件，报错 put: […]