用了很久的hadoop都没问题，装完新东西之后突然打不开？

hadoop拒绝访问？

Permission denied (publickey,password)

root@192.168.78.131’s password:
Permission denied, please try again.
root@192.168.78.131’s password:
Permission denied, please try again.
root@192.168.78.131’s password:
root@192.168.78.131: Permission denied (publickey,password).

hadoop用户启动不了，用sudo更启动不了？

sudo ./sbin/start-dfs.sh
[sudo] hadoop 的密码： 
debug3: receive packet: type 2
debug3: Received SSH2_MSG_IGNORE
debug3: receive packet: type 2
debug3: Received SSH2_MSG_IGNORE

Starting namenodes on [localhost]
ERROR: Attempting to operate on hdfs namenode as root
ERROR: but there is no HDFS_NAMENODE_USER defined. Aborting operation.
Starting datanodes
ERROR: Attempting to operate on hdfs datanode as root
ERROR: but there is no HDFS_DATANODE_USER defined. Aborting operation.
Starting secondary namenodes [ubuntu]
ERROR: Attempting to operate on hdfs secondarynamenode as root
ERROR: but there is no HDFS_SECONDARYNAMENODE_USER defined. Aborting operation.

考虑如下原因

Remote: Ignored authorized keys: bad ownership or modes for file /home/hadoop/.ssh/authorized_keys

尝试以下代码：

cd .ssh
chmod 0600 *

问题成功解决