我使用本教程在一台机器上安装了hadoop 2.2：http://www.michael-noll.com/tutorials/running-hadoop-on-ubuntu-linux-single-node-cluster/
一些细节做了一些改变，例如，我使用了java8、/hadoop root dir等，users、ssh、config key都是一样的。
namenode已成功格式化：

13/12/22 05:42:31 INFO common.Storage: Storage directory /hadoop/tmp/dfs/name has been successfully formatted.
13/12/22 05:42:31 INFO namenode.FSImage: Saving image file /hadoop/tmp/dfs/name/current/fsimage.ckpt_0000000000000000000 using no compression
13/12/22 05:42:32 INFO namenode.FSImage: Image file /hadoop/tmp/dfs/name/current/fsimage.ckpt_0000000000000000000 of size 198 bytes saved in 0 seconds.
13/12/22 05:42:32 INFO namenode.NNStorageRetentionManager: Going to retain 1 images with txid >= 0
13/12/22 05:42:32 INFO util.ExitUtil: Exiting with status 0
13/12/22 05:42:32 INFO namenode.NameNode: SHUTDOWN_MSG:

但是，“mkdir”和“ls”命令都不起作用：

$ /hadoop/hadoop/bin/hadoop fs -ls
Java HotSpot(TM) 64-Bit Server VM warning: You have loaded library /hadoop/hadoop-2.2.0/lib/native/libhadoop.so.1.0.0 which might have disabled stack guard. The VM will try to fix the stack guard now.
It's highly recommended that you fix the library with 'execstack -c <libfile>', or link it with '-z noexecstack'.
13/12/22 05:39:33 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
ls: `.': No such file or directory

谢谢你们的帮助。