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1 FATAL org.apache.hadoop.ha.ZKFailoverController: Unable to start failover controller. Parent znode does not exist.
这个错误导致启动不了DFSZKFailoverController，从而不能选举出Active Node，导致了Hadoop两个NameNode都是Standby，我是这样做的
停掉Hadoop所有进程，然后重新格式化Zookeeper
hdfs zkfc -formatZK
2 紧接着上个问题，再重新格式化过zookeeper之后，发现yarn启动不了了
2015-08-05 19:00:33,718 INFO org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore: Exception while executing a ZK operation. org.apache.zookeeper.KeeperException$NoNodeException: KeeperErrorCode = NoNode at org.apache.zookeeper.KeeperException.create(KeeperException.java:111) at org.apache.zookeeper.ZooKeeper.multiInternal(ZooKeeper.java:949) at org.apache.zookeeper.ZooKeeper.multi(ZooKeeper.java:915) at org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore$4.run(ZKRMStateStore.java:937) at org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore$4.run(ZKRMStateStore.java:934) at org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore$ZKAction.runWithCheck(ZKRMStateStore.java:1076) at org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore$ZKAction.runWithRetries(ZKRMStateStore.java:1095) at org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore.doMultiWithRetries(ZKRMStateStore.java:934) at org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore.doMultiWithRetries(ZKRMStateStore.java:948) at org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore.removeRMDTMasterKeyState(ZKRMStateStore.java:844) at org.apache.hadoop.yarn.server.resourcemanager.recovery.RMStateStore.removeRMDTMasterKey(RMStateStore.java:733) at org.apache.hadoop.yarn.server.resourcemanager.security.RMDelegationTokenSecretManager.removeStoredMasterKey(RMDelegationTokenSecretManager.java:99) at org.apache.hadoop.security.token.delegation.AbstractDelegationTokenSecretManager.removeExpiredKeys(AbstractDelegationTokenSecretManager.java:371) at org.apache.hadoop.security.token.delegation.AbstractDelegationTokenSecretManager.rollMasterKey(AbstractDelegationTokenSecretManager.java:348) at org.apache.hadoop.security.token.delegation.AbstractDelegationTokenSecretManager$ExpiredTokenRemover.run(AbstractDelegationTokenSecretManager.java:646) at java.lang.Thread.run(Thread.java:745) 2015-08-05 19:00:33,718 INFO org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore: Maxed out ZK retries. Giving up! 2015-08-05 19:00:33,718 INFO org.apache.hadoop.yarn.server.resourcemanager.security.RMDelegationTokenSecretManager: removing master key with keyID 55 2015-08-05 19:00:33,738 INFO org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore: Exception while executing a ZK operation. org.apache.zookeeper.KeeperException$NoNodeException: KeeperErrorCode = NoNode at org.apache.zookeeper.KeeperException.create(KeeperException.java:111) at org.apache.zookeeper.ZooKeeper.multiInternal(ZooKeeper.java:949) at org.apache.zookeeper.ZooKeeper.multi(ZooKeeper.java:915) at org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore$4.run(ZKRMStateStore.java:937) at org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore$4.run(ZKRMStateStore.java:934) at org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore$ZKAction.runWithCheck(ZKRMStateStore.java:1076) at org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore$ZKAction.runWithRetries(ZKRMStateStore.java:1095) at org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore.doMultiWithRetries(ZKRMStateStore.java:934) at org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore.doMultiWithRetries(ZKRMStateStore.java:948) at org.apache.hadoop.yarn.server.resourcemanager.recovery.ZKRMStateStore.removeRMDTMasterKeyState(ZKRMStateStore.java:844) at org.apache.hadoop.yarn.server.resourcemanager.recovery.RMStateStore.removeRMDTMasterKey(RMStateStore.java:733) at org.apache.hadoop.yarn.server.resourcemanager.security.RMDelegationTokenSecretManager.removeStoredMasterKey(RMDelegationTokenSecretManager.java:99) at org.apache.hadoop.security.token.delegation.AbstractDelegationTokenSecretManager.removeExpiredKeys(AbstractDelegationTokenSecretManager.java:371) at org.apache.hadoop.security.token.delegation.AbstractDelegationTokenSecretManager.rollMasterKey(AbstractDelegationTokenSecretManager.java:348) at org.apache.hadoop.security.token.delegation.AbstractDelegationTokenSecretManager$ExpiredTokenRemover.run(AbstractDelegationTokenSecretManager.java:646) at java.lang.Thread.run(Thread.java:745)
但是这个问题，估计还是因为zookeeper造成的，但是我没任何修改，从新启动yarn。。。竟然成功了
start-yarn.sh
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原文地址：http://www.cnblogs.com/liuchangchun/p/4705723.html
