接着一，继续记录hadoop环境遇到的一些问题。
1. 报错信息：Hadoop-Error: Could not find or load main class org.apache.hadoop.mapreduce.v2.app.MRAppMaster
根据报错提示找到hadoop安装目录下$HADOOP_HOME/etc/hadoop/mapred-site.xml,增加以下代码
<property> <name>yarn.app.mapreduce.am.env</name> <value>HADOOP_MAPRED_HOME=${HADOOP_HOME}</value> </property> <property> <name>mapreduce.map.env</name> <value>HADOOP_MAPRED_HOME=${HADOOP_HOME}</value> </property> <property> <name>mapreduce.reduce.env</name> <value>HADOOP_MAPRED_HOME=${HADOOP_HOME}</value> </property>
2. 报错信息：MapReduce报错Exception in thread "main" java.lang.UnsatisfiedLinkError: org.apache.hadoop.io.nativeio
log4j:WARN No appenders could be found for logger (org.apache.hadoop.metrics2.lib.MutableMetricsFactory). log4j:WARN Please initialize the log4j system properly. log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info. Exception in thread "main" java.lang.UnsatisfiedLinkError: org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Ljava/lang/String;I)Z at org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Native Method) at org.apache.hadoop.io.nativeio.NativeIO$Windows.access(NativeIO.java:609) at org.apache.hadoop.fs.FileUtil.canRead(FileUtil.java:977) at org.apache.hadoop.util.DiskChecker.checkAccessByFileMethods(DiskChecker.java:187) at org.apache.hadoop.util.DiskChecker.checkDirAccess(DiskChecker.java:174) at org.apache.hadoop.util.DiskChecker.checkDir(DiskChecker.java:108) at org.apache.hadoop.fs.LocalDirAllocator$AllocatorPerContext.confChanged(LocalDirAllocator.java:285) at org.apache.hadoop.fs.LocalDirAllocator$AllocatorPerContext.getLocalPathForWrite(LocalDirAllocator.java:344) at org.apache.hadoop.fs.LocalDirAllocator.getLocalPathForWrite(LocalDirAllocator.java:150) at org.apache.hadoop.fs.LocalDirAllocator.getLocalPathForWrite(LocalDirAllocator.java:131) at org.apache.hadoop.fs.LocalDirAllocator.getLocalPathForWrite(LocalDirAllocator.java:115) at org.apache.hadoop.mapred.LocalDistributedCacheManager.setup(LocalDistributedCacheManager.java:125) at org.apache.hadoop.mapred.LocalJobRunner$Job.<init>(LocalJobRunner.java:163) at org.apache.hadoop.mapred.LocalJobRunner.submitJob(LocalJobRunner.java:731) at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:240) at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1290) at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1287) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:422) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1746) at org.apache.hadoop.mapreduce.Job.submit(Job.java:1287) at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1308) at com.runner.WordCountRunner.main(WordCountRunner.java:45) Process finished with exit code 1
出现原因：在新版本的windows系统中，会取消部分文件，某些功能无法支持。本地的NativeIO无法写入，我们需要再写一个NativeIO的类，放入代码片段的包中
3. ExitCodeException exitCode=-1073741515
解决方法：
win10配置hadoop 想直接在本地运行报错，提示操作系统缺少 msvcr100.dll文件，去网上找到 msvcr100.dll 文件安装；
网盘提取地址：https://pan.baidu.com/s/1kXyHu3-kAoCCPAJuS9vSZw提取码：x4eg
如果没有效果只能安装常用C++库合集（x86 + 64位）
链接：https://pan.baidu.com/s/12fMY_n3UQQPqkbNLQjUV3Q提取码：4jqw按照提示安装即可
