hadoop出现namenode running as process 18472. Stop it first.等等，类别似几个的出现。
namenode running as process 32972. Stop it first.
127.0.0.1: ssh: connect to host 127.0.0.1 port 22: No error
127.0.0.1: ssh: connect to host 127.0.0.1 port 22: No error
jobtracker running as process 81312. Stop it first.
127.0.0.1: ssh: connect to host 127.0.0.1 port 22: No error
解决的方法：说明你没有启动起来，所以在启动之前你须要 在又一次启动hadoop之前要先stop掉全部的hadoop服务。
然后返回到正常启动。
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