必须指定要使用的jar文件的类名：

hadoop jar pathtojarfile classname arg1 arg2 ..

例子：

hadoop jar example.jar wordcount inputPath outputPath

@阿努普。jar文件的完整/相对路径是必需的。
在您的例子中，它可能是/home/user/hadoop/share/hadoop--examples.jar
hadoop目录中的完整命令可能是
/home/user/hadoop/bin/hadoop/home/user/hadoop/share/hadoop--examples.jar
（我在这里使用了绝对完整路径，但是可以使用相对路径）。

这很可能是配置问题或使用无效的文件路径。
很可能hadoop-*-examples.jar的名称不正确，因为在我的hadoop（1.0.0）版本中，文件名是hadoop-examples-1.0.0.jar。
因此，我运行以下命令列出所有示例，它的工作原理与charm类似：

bin/hadoop jar hadoop-examples-*.jar 

An example program must be given as the first argument.
Valid program names are:
  aggregatewordcount: An Aggregate based map/reduce program that counts the words in the input files.
  aggregatewordhist: An Aggregate based map/reduce program that computes the histogram of the words in the input files.
  dbcount: An example job that count the pageview counts from a database.
  grep: A map/reduce program that counts the matches of a regex in the input.
  join: A job that effects a join over sorted, equally partitioned datasets
  multifilewc: A job that counts words from several files.
  pentomino: A map/reduce tile laying program to find solutions to pentomino problems.
  pi: A map/reduce program that estimates Pi using monte-carlo method.
  randomtextwriter: A map/reduce program that writes 10GB of random textual data per node.
  randomwriter: A map/reduce program that writes 10GB of random data per node.
  secondarysort: An example defining a secondary sort to the reduce.
  sleep: A job that sleeps at each map and reduce task.
  sort: A map/reduce program that sorts the data written by the random writer.
  sudoku: A sudoku solver.
  teragen: Generate data for the terasort
  terasort: Run the terasort
  teravalidate: Checking results of terasort
  wordcount: A map/reduce program that counts the words in the input files.

另外，如果我使用与您相同的文件名模式，则会出现错误：

bin/hadoop jar hadoop-*examples.jar 

Exception in thread "main" java.io.IOException: Error opening job jar: hadoop-*examples.jar

hth公司

你会发现jar在里面 $HADOOP_HOME/share/hadoop/mapreduce/hadoop-*-examples*.jar