我机子上的hadoop安装有一阶段了，由于前几天发现机子上垃圾太多，自己给清理了一下，一不小心不知道清除了什么，导致我的hadoop无法正常启动了。每次执行start-all.sh都会报错，而且还让我重新输入密码。今天早上过来，我又试试，输入SSH localhost命令（纯属凑巧），发现让我输入密码。我当时就想，这个玩意儿在安装hadoop环境的时候不是已经安装过吗？而且还是防止以后重复输入密码的方式。于是我又重新执行了一遍： ssh-keygen -t dsa -P '' -f ~/.ssh/id_dsa 。估计问题是找到了。试了下start-all.sh，ok一切都正常！
Administrator@f523540 /cygdrive/d/hadoop-0.20.2/bin
$ start-all.sh
starting namenode, logging to /cygdrive/d/hadoop-0.20.2/bin/../hadoop_logs/hadoo
p-Administrator-namenode-f523540.out
cygwin warning:
MS-DOS style path detected: D:\hadoop-0.20.2\/build/native
Preferred POSIX equivalent is: /cygdrive/d/hadoop-0.20.2/build/native
CYGWIN environment variable option "nodosfilewarning" turns off this warning.
Consult the user's guide for more details about POSIX paths:
http://cygwin.com/cygwin-ug-net/using.html#using-pathnames
localhost: starting datanode, logging to /cygdrive/d/hadoop-0.20.2/bin/../hadoop
_logs/hadoop-Administrator-datanode-f523540.out
localhost: starting secondarynamenode, logging to /cygdrive/d/hadoop-0.20.2/bin/
../hadoop_logs/hadoop-Administrator-secondarynamenode-f523540.out
starting jobtracker, logging to /cygdrive/d/hadoop-0.20.2/bin/../hadoop_logs/had
oop-Administrator-jobtracker-f523540.out
localhost: starting tasktracker, logging to /cygdrive/d/hadoop-0.20.2/bin/../had
oop_logs/hadoop-Administrator-tasktracker-f523540.out
just enjoy it!~~~~~~~~~~