1.Exception in thread "main" java.net.ConnectException: Call to master/192.168.1.101:9000 failed on connection exception: java.net.ConnectException: 拒绝连接
at org.apache.hadoop.ipc.Client.wrapException(Client.java:1142)
at org.apache.hadoop.ipc.Client.call(Client.java:1118)
at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:229)
at com.sun.proxy.$Proxy1.getProtocolVersion(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:85)
hadoop的hdfs没启动，
启动hdfs：到bin目录执行start-dfs.sh
执行命令读取文件内容：
报错[root@localhost bin]# ../bin/hadoop URLCat hdfs://192.168.1.101:9000/root/in/test1.txt
Exception in thread "main" java.io.FileNotFoundException: File does not exist: /root/in/test1.txt
at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.fetchLocatedBlocks(DFSClient.java:2006)
at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.openInfo(DFSClient.java:1975)
at org.apache.hadoop.hdfs.DFSClient$DFSInputStream.<init>(DFSClient.java:1967)
at org.apache.hadoop.hdfs.DFSClient.open(DFSClient.java:735)
at org.apache.hadoop.hdfs.DistributedFileSystem.open(DistributedFileSystem.java:165)
at org.apache.hadoop.fs.FileSystem.open(FileSystem.java:436)
at org.apache.hadoop.fs.FsUrlConnection.connect(FsUrlConnection.java:46)
at org.apache.hadoop.fs.FsUrlConnection.getInputStream(FsUrlConnection.java:56)
at java.net.URL.openStream(URL.java:1037)
at URLCat.main(URLCat.java:15)
其实 文件test1.txt是存在的。
原因：没有把本地文件放到hdfs文件系统内。所以需要本地文件通过hadoop的命令存放到hdfs上。
（1）.创建本地文件，当前目录是/usr/local/hadoop1.2.1目录
mkdir input //创建input目录
cd input //到input目录上
echo "hello world ">test1.txt //字符串内不能包含感叹号（!），bash命令无法解析
echo "hello hadoop">test2.txt
（2）.创建好文件后，通过hadoop命令本地文件放到hdfs系统上,当前目录：usr/local/hadoop1.2.1目录
bin/hadoop fs -put input ./in //放到hdf上
bin/hadoop fs -ls //检查hdfs文件
运行结果为：
Found 1 items
drwxr-xr-x - root supergroup 0 2015-05-17 01:11 /user/root/in
bin/hadoop fs -cat ./in/test1.txt //查看文件内容
（3）.通过hadoop提供的例子，读取刚上传的hdf文件的内容，统计单词
bin/hadoop jar hadoop-examples-1.2.1.jar wordcount in out //统计in目录下，文件内容的单词数量
运行结果为：
15/05/17 01:13:40 INFO input.FileInputFormat: Total input paths to process : 2
15/05/17 01:13:40 INFO util.NativeCodeLoader: Loaded the native-hadoop library
15/05/17 01:13:40 WARN snappy.LoadSnappy: Snappy native library not loaded
15/05/17 01:13:41 INFO mapred.JobClient: Running job: job_201505170049_0001
15/05/17 01:13:42 INFO mapred.JobClient: map 0% reduce 0%
15/05/17 01:13:52 INFO mapred.JobClient: map 100% reduce 0%
15/05/17 01:14:28 INFO mapred.JobClient: map 100% reduce 100%
15/05/17 01:14:31 INFO mapred.JobClient: Job complete: job_201505170049_0001
15/05/17 01:14:31 INFO mapred.JobClient: Counters: 29
15/05/17 01:14:31 INFO mapred.JobClient: Job Counters
15/05/17 01:14:31 INFO mapred.JobClient: Launched reduce tasks=1
15/05/17 01:14:31 INFO mapred.JobClient: SLOTS_MILLIS_MAPS=14618
15/05/17 01:14:31 INFO mapred.JobClient: Total time spent by all reduces waiting after reserving slots (ms)=0
15/05/17 01:14:31 INFO mapred.JobClient: Total time spent by all maps waiting after reserving slots (ms)=0
15/05/17 01:14:31 INFO mapred.JobClient: Launched map tasks=2
15/05/17 01:14:31 INFO mapred.JobClient: Data-local map tasks=2
15/05/17 01:14:31 INFO mapred.JobClient: SLOTS_MILLIS_REDUCES=27918
15/05/17 01:14:31 INFO mapred.JobClient: File Output Format Counters
15/05/17 01:14:31 INFO mapred.JobClient: Bytes Written=25
15/05/17 01:14:31 INFO mapred.JobClient: FileSystemCounters
15/05/17 01:14:31 INFO mapred.JobClient: FILE_BYTES_READ=55
15/05/17 01:14:31 INFO mapred.JobClient: HDFS_BYTES_READ=241
15/05/17 01:14:31 INFO mapred.JobClient: FILE_BYTES_WRITTEN=173312
15/05/17 01:14:31 INFO mapred.JobClient: HDFS_BYTES_WRITTEN=25
15/05/17 01:14:31 INFO mapred.JobClient: File Input Format Counters
15/05/17 01:14:31 INFO mapred.JobClient: Bytes Read=25
15/05/17 01:14:31 INFO mapred.JobClient: Map-Reduce Framework
15/05/17 01:14:31 INFO mapred.JobClient: Map output materialized bytes=61
15/05/17 01:14:31 INFO mapred.JobClient: Map input records=2
15/05/17 01:14:31 INFO mapred.JobClient: Reduce shuffle bytes=61
15/05/17 01:14:31 INFO mapred.JobClient: Spilled Records=8
15/05/17 01:14:31 INFO mapred.JobClient: Map output bytes=41
15/05/17 01:14:31 INFO mapred.JobClient: Total committed heap usage (bytes)=415969280
15/05/17 01:14:31 INFO mapred.JobClient: CPU time spent (ms)=1550
15/05/17 01:14:31 INFO mapred.JobClient: Combine input records=4
15/05/17 01:14:31 INFO mapred.JobClient: SPLIT_RAW_BYTES=216
15/05/17 01:14:31 INFO mapred.JobClient: Reduce input records=4
15/05/17 01:14:31 INFO mapred.JobClient: Reduce input groups=3
15/05/17 01:14:31 INFO mapred.JobClient: Combine output records=4
15/05/17 01:14:31 INFO mapred.JobClient: Physical memory (bytes) snapshot=318287872
15/05/17 01:14:31 INFO mapred.JobClient: Reduce output records=3
15/05/17 01:14:31 INFO mapred.JobClient: Virtual memory (bytes) snapshot=1041612800
15/05/17 01:14:31 INFO mapred.JobClient: Map output records=4
[root@backup01 hadoop-1.2.1]# bin/hadoop fs -ls
Found 2 items
drwxr-xr-x - root supergroup 0 2015-05-17 01:11 /user/root/in
drwxr-xr-x - root supergroup 0 2015-05-17 01:14 /user/root/out
[root@backup01 hadoop-1.2.1]# bin/hadoop fs -ls ./out
Found 3 items
-rw-r--r-- 1 root supergroup 0 2015-05-17 01:14 /user/root/out/_SUCCESS
drwxr-xr-x - root supergroup 0 2015-05-17 01:13 /user/root/out/_logs
-rw-r--r-- 1 root supergroup 25 2015-05-17 01:14 /user/root/out/part-r-00000
[root@backup01 hadoop-1.2.1]# bin/hadoop fs -cat ./out/part-r-00000
hadoop 1
hello 2
world 1