这是因为zookeeper已经在运行，您可以使用

  ps aux | grep zookeeper 
 $ p检查该过程$ p> 

并手动终止该过程，它将起作用。
 
I'm using confluent platform, the zookeeper is active with status lookup. but when I try to start kafka with confluent it shows zookeeper is down.
$ sudo service zookeeper status
Redirecting to /bin/systemctl status  zookeeper.service
● zookeeper.service - Zookeeper
   Loaded: loaded (/etc/systemd/system/zookeeper.service; disabled; vendor preset: disabled)
   Active: active (running) since Tue 2017-08-08 17:25:34 PDT; 16h ago
     Docs: http://kafka.apache.org/documentation.html
  Process: 3774 ExecStop=/var/www/confluent/bin/zookeeper-server-stop (code=exited, status=1/FAILURE)
 Main PID: 3785 (java)
   CGroup: /system.slice/zookeeper.service
           └─3785 java -Xmx512M -Xms512M -server -XX:+UseG1GC -XX:MaxGCPauseMillis=20 -XX:InitiatingHeapOccupancyPercent=35 -XX:+DisableExplicitGC -Djava.awt.headless=true -Xloggc:/var/log...

 zookeeper[3785]: [2017-08-08 17:26:09,005] INFO Processed session termination for sessionid: 0x15dc460fd0c0000 (org.apache.zooke...Processor)
 zookeeper[3785]: [2017-08-08 17:26:39,000] INFO Expiring session 0x15dc4364baf0004, timeout of 60000ms exceeded (org.apache.zook...perServer)
 zookeeper[3785]: [2017-08-08 17:26:39,000] INFO Expiring session 0x15dc4364baf0002, timeout of 60000ms exceeded (org.apache.zook...perServer)
 zookeeper[3785]: [2017-08-08 17:26:39,000] INFO Expiring session 0x15dc4364baf0003, timeout of 60000ms exceeded (org.apache.zook...perServer)
 zookeeper[3785]: [2017-08-08 17:26:39,001] INFO Processed session termination for sessionid: 0x15dc4364baf0004 (org.apache.zooke...Processor)
 zookeeper[3785]: [2017-08-08 17:26:39,002] INFO Processed session termination for sessionid: 0x15dc4364baf0002 (org.apache.zooke...Processor)
 zookeeper[3785]: [2017-08-08 17:26:39,002] INFO Processed session termination for sessionid: 0x15dc4364baf0003 (org.apache.zooke...Processor)
 zookeeper[3785]: [2017-08-09 09:56:26,711] INFO Accepted socket connection from /127.0.0.1:46446 (org.apache.zookeeper.server.NI...xnFactory)
 zookeeper[3785]: [2017-08-09 09:59:14,796] WARN Exception causing close of session 0x0 due to java.io.IOException: Len error -72...erverCnxn)
 zookeeper[3785]: [2017-08-09 09:59:14,796] INFO Closed socket connection for client /127.0.0.1:46446 (no session established for...erverCnxn)
Hint: Some lines were ellipsized, use -l to show in full.


$ confluent start kafka
Starting zookeeper
|Zookeeper failed to start
zookeeper is [DOWN]
Cannot start Kafka, Zookeeper is not running. Check your deployment

This is because zookeeper is already running, you can check the process with 
ps aux|grep zookeeper
and kill the process manually and it is gonna work.