原文链接：https://www.cnblogs.com/sunddenly/p/4031881.html
Zookeeper支持某些特定的四字命令字母与其的交互。他们大多数是查询命令，用来获取Zookeeper服务的当前状态及相关信息。用户在客户端可以通过telnet或nc向Zookeeper提交相应的命令。Zookeeper常用的四字命令见下图所示。
上图，是Zookeeper四字命令的一个简单用例。
[root@hadoop ~]# echo ruok|nc localhost 2181 [root@hadoop ~]# zkServer.sh start zoo1.cfg JMX enabled by default Using config: /usr/local/zk/bin/../conf/zoo1.cfg Starting zookeeper ... STARTED [root@hadoop ~]# zkServer.sh start zoo2.cfg JMX enabled by default Using config: /usr/local/zk/bin/../conf/zoo2.cfg Starting zookeeper ... STARTED [root@hadoop ~]# zkServer.sh start zoo3.cfg JMX enabled by default Using config: /usr/local/zk/bin/../conf/zoo3.cfg Starting zookeeper ... STARTED [root@hadoop ~]# echo ruok|nc localhost 2181 imok[root@hadoop ~]# echo ruok|nc localhost 2182 imok[root@hadoop ~]# echo ruok|nc localhost 2183 imok[root@hadoop ~]# echo conf|nc localhost 2181 clientPort=2181 dataDir=/usr/local/zk/data_1/version-2 dataLogDir=/usr/local/zk/logs_1/version-2 tickTime=2000 maxClientCnxns=60 minSessionTimeout=4000 maxSessionTimeout=40000 serverId=0 initLimit=10 syncLimit=5 electionAlg=3 electionPort=3387 quorumPort=2287 peerType=0 [root@hadoop ~]#
二、Zookeeper的简单操作
2.1 Zookeeper的shell操作
2.1.1 Zookeeper命令工具
再启动Zookeeper服务之后，输入以下命令，连接到Zookeeper服务：
zkCli.sh -server localhost:2181
执行结果如下所示：
[root@hadoop ~]# zkCli.sh -server localhost:2181 Connecting to localhost:2181 2014-10-17 03:35:51,051 [myid:] - INFO [main:Environment@100] - Client environment:zookeeper.version=3.4.5-1392090, built on 09/30/2012 17:52 GMT 2014-10-17 03:35:51,055 [myid:] - INFO [main:Environment@100] - Client environment:host.name=hadoop 2014-10-17 03:35:51,057 [myid:] - INFO [main:Environment@100] - Client environment:java.version=1.6.0_24 2014-10-17 03:35:51,057 [myid:] - INFO [main:Environment@100] - Client environment:java.vendor=Sun Microsystems Inc. 2014-10-17 03:35:51,066 [myid:] - INFO [main:Environment@100] - Client environment:java.home=/usr/local/jdk/jre 2014-10-17 03:35:51,079 [myid:] - INFO [main:Environment@100] - Client environment:java.class.path=/usr/local/zk/bin/../build/classes:/usr/local/zk/bin/../build/lib/*.jar:/usr/local/zk/bin/../lib/slf4j-log4j12-1.6.1.jar:/usr/local/zk/bin/../lib/slf4j-api-1.6.1.jar:/usr/local/zk/bin/../lib/netty-3.2.2.Final.jar:/usr/local/zk/bin/../lib/log4j-1.2.15.jar:/usr/local/zk/bin/../lib/jline-0.9.94.jar:/usr/local/zk/bin/../zookeeper-3.4.5.jar:/usr/local/zk/bin/../src/java/lib/*.jar:/usr/local/zk/bin/../conf: 2014-10-17 03:35:51,083 [myid:] - INFO [main:Environment@100] - Client environment:java.library.path=/usr/local/jdk/jre/lib/i386/client:/usr/local/jdk/jre/lib/i386:/usr/local/jdk/jre/../lib/i386:/usr/java/packages/lib/i386:/lib:/usr/lib 2014-10-17 03:35:51,084 [myid:] - INFO [main:Environment@100] - Client environment:java.io.tmpdir=/tmp 2014-10-17 03:35:51,086 [myid:] - INFO [main:Environment@100] - Client environment:java.compiler=<NA> 2014-10-17 03:35:51,099 [myid:] - INFO [main:Environment@100] - Client environment:os.name=Linux 2014-10-17 03:35:51,100 [myid:] - INFO [main:Environment@100] - Client environment:os.arch=i386 2014-10-17 03:35:51,101 [myid:] - INFO [main:Environment@100] - Client environment:os.version=2.6.32-358.el6.i686 2014-10-17 03:35:51,101 [myid:] - INFO [main:Environment@100] - Client environment:user.name=root 2014-10-17 03:35:51,102 [myid:] - INFO [main:Environment@100] - Client environment:user.home=/root 2014-10-17 03:35:51,106 [myid:] - INFO [main:Environment@100] - Client environment:user.dir=/root 2014-10-17 03:35:51,120 [myid:] - INFO [main:ZooKeeper@438] - Initiating client connection, connectString=localhost:2181 sessionTimeout=30000 watcher=org.apache.zookeeper.ZooKeeperMain$MyWatcher@b02e7a Welcome to ZooKeeper! JLine support is enabled 2014-10-17 03:35:51,233 [myid:] - INFO [main-SendThread(localhost:2181):ClientCnxn$SendThread@966] - Opening socket connection to server localhost/127.0.0.1:2181. Will not attempt to authenticate using SASL (Unable to locate a login configuration) 2014-10-17 03:35:51,247 [myid:] - INFO [main-SendThread(localhost:2181):ClientCnxn$SendThread@849] - Socket connection established to localhost/127.0.0.1:2181, initiating session [zk: localhost:2181(CONNECTING) 0] 2014-10-17 03:35:51,290 [myid:] - INFO [main-SendThread(localhost:2181):ClientCnxn$SendThread@1207] - Session establishment complete on server localhost/127.0.0.1:2181, sessionid = 0x491da0e20b0000, negotiated timeout = 30000 WATCHER:: WatchedEvent state:SyncConnected type:None path:null [zk: localhost:2181(CONNECTED) 0]