Hadoop 预装示例 Jars

Question

我刚刚在本地机器上成功设置了 Hadoop。我正在关注我刚买的一本畅销书中的一个例子。我正在尝试获取安装附带的所有 hadoop 示例的列表。为此，我键入以下命令:

bin/hadoop jar hadoop-*-examples.jar

输入此内容后，我应该会得到一个 Hadoop 示例列表，对吗？然而，我所看到的只是这条错误信息:

Not a valid JAR: /home/user/hadoop/hadoop-*-examples.jar

我该如何解决这个问题？这只是一个简单的权限问题吗？

Answer 1

这很可能是配置问题或使用了无效的文件路径。

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。

所以我运行了以下命令来列出所有示例，它就像魅力一样:

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.

此外，如果我使用与您相同的文件名模式，我会收到错误消息:

bin/hadoop jar hadoop-*examples.jar 

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

HTH