[root@slave-2 bin]# ./zkServer.sh start
ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper-3.4.10/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED

但是zookeeper的進程和端口都沒有起來。

查看zookeeper.out，發現有報錯信息如下：

2018-05-07 10:33:58,556 [myid:3] - INFO  [main:FileSnap@83] - Reading snapshot /opt/data/zookeeper/version-2/snapshot.1900356f19
2018-05-07 10:33:58,966 [myid:3] - ERROR [main:Util@239] - Last transaction was partial.
2018-05-07 10:33:58,968 [myid:3] - ERROR [main:QuorumPeer@648] - Unable to load database on disk
java.io.IOException: The accepted epoch, 19 is less than the current epoch, 3a
    at org.apache.zookeeper.server.quorum.QuorumPeer.loadDataBase(QuorumPeer.java:645)
    at org.apache.zookeeper.server.quorum.QuorumPeer.start(QuorumPeer.java:591)
    at org.apache.zookeeper.server.quorum.QuorumPeerMain.runFromConfig(QuorumPeerMain.java:164)
    at org.apache.zookeeper.server.quorum.QuorumPeerMain.initializeAndRun(QuorumPeerMain.java:111)
    at org.apache.zookeeper.server.quorum.QuorumPeerMain.main(QuorumPeerMain.java:78)
2018-05-07 10:33:58,970 [myid:3] - ERROR [main:QuorumPeerMain@89] - Unexpected exception, exiting abnormally
java.lang.RuntimeException: Unable to run quorum server 
    at org.apache.zookeeper.server.quorum.QuorumPeer.loadDataBase(QuorumPeer.java:649)
    at org.apache.zookeeper.server.quorum.QuorumPeer.start(QuorumPeer.java:591)
    at org.apache.zookeeper.server.quorum.QuorumPeerMain.runFromConfig(QuorumPeerMain.java:164)
    at org.apache.zookeeper.server.quorum.QuorumPeerMain.initializeAndRun(QuorumPeerMain.java:111)
    at org.apache.zookeeper.server.quorum.QuorumPeerMain.main(QuorumPeerMain.java:78)
Caused by: java.io.IOException: The accepted epoch, 19 is less than the current epoch, 3a
    at org.apache.zookeeper.server.quorum.QuorumPeer.loadDataBase(QuorumPeer.java:645)
    ... 4 more
[root@slave-2 bin]# 
 

經過網上查詢，得到解決方法：
將zookeeper的version-2目錄備份一份，再重新創建一個新的version-2目錄，然後重新啟動zookeeper。

操作如下：

[root@slave-2 zookeeper]# ll
total 28
-rw-r--r-- 1 root root     2 Aug 30  2017 myid
drwxr-xr-x 2 root root 24576 May  7 10:36 version-2
-rw-r--r-- 1 root root     5 May  7 10:42 zookeeper_server.pid
[root@slave-2 zookeeper]# mv version-2 version-2.bak
[root@slave-2 zookeeper]# ll
total 28
-rw-r--r-- 1 root root     2 Aug 30  2017 myid
drwxr-xr-x 2 root root 24576 May  7 10:36 version-2.bak
-rw-r--r-- 1 root root     5 May  7 10:42 zookeeper_server.pid
[root@slave-2 zookeeper]# mkdir version-2
[root@slave-2 zookeeper]# ll
total 28
-rw-r--r-- 1 root root     2 Aug 30  2017 myid
drwxr-xr-x 2 root root     6 May  7 10:44 version-2
drwxr-xr-x 2 root root 24576 May  7 10:36 version-2.bak
-rw-r--r-- 1 root root     5 May  7 10:42 zookeeper_server.pid
 

然後重新啟動zookeeper：

[root@slave-2 bin]# ./zkServer.sh start
ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper-3.4.10/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
[root@slave-2 bin]# netstat -tlunp|grep 2181
tcp6       0      0 :::2181                 :::*                    LISTEN      32695/java
 

ZK—zookeeper無法啟動，報“Unable to load database on dis”