在ubuntu16.4下spark的单机/伪分布式配置我在此就不在一一赘述，详情请点击如下连接：
Hadoop安装教程_单机/伪分布式配置_Hadoop2.6.0/Ubuntu14.04
我出现问题是在配置好伪分布式的文件并且NameNode 的格式化正确我弄成后，在启动hdfs时出现如下错误：
hadoop@litao-virtual-machine:/usr/local/hadoop$ ./sbin/start-dfs.sh Starting namenodes on [localhost] localhost: Error: JAVA_HOME is not set and could not be found. localhost: Error: JAVA_HOME is not set and could not be found. Starting secondary namenodes [0.0.0.0] 0.0.0.0: Error: JAVA_HOME is not set and could not be found.
此错误多出现于你的java环境没有配置正确的时候，关于如何正确配置ubuntu下的java请出门右转问百度。
当你的环境是ubuntu16.4 hadoop2.7.4 并且java已经确保正确配置时，（网上其它关于次报错的解决办法都尝试过时）或许下面我的解决办法会让你柳暗花明：
1 vim ./etc/hadoop/hadoop-env.sh #打开你hadoop安装路径下的hadoop环境配置脚本 2 3 # The only required environment variable is JAVA_HOME. All others are 4 # optional. When running a distributed configuration it is best to 5 # set JAVA_HOME in this file, so that it is correctly defined on 6 # remote nodes. 7 8 # The java implementation to use. 9 JAVA_HOME=/usr/local/java/jdk1.8.0_151 #你的java路径 10 export JAVA_HOME #添加这两行内容 11 export JAVA_HOME=${JAVA_HOME} 12 13 # The jsvc implementation to use. Jsvc is required to run secure datanodes
之后就可以重新执行:
./sbin/start-dfs.sh
#由于我在写博客时已经运行过，所以会提示已经运行
1 hadoop@litao-virtual-machine:/usr/local/hadoop$ ./sbin/start-dfs.sh 2 Starting namenodes on [localhost] 3 localhost: namenode running as process 5085. Stop it first. 4 localhost: datanode running as process 5239. Stop it first. 5 Starting secondary namenodes [0.0.0.0] 6 0.0.0.0: secondarynamenode running as process 5407. Stop it first.
问题原因：
根因未知，知识在检查机子各项配置没有问题之后，加上各种猜测性测试得到的解决办法。
希望本条微博可以给您带来帮助！
