Confirm Hosts阶段
/etc/hosts前两行必须是
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
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ERROR 2018-03-08 15:02:25,223 NetUtil.py:88 - [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:579)
ERROR 2018-03-08 15:02:25,223 NetUtil.py:89 - SSLError: Failed to connect. Please check openssl library versions.
有可能是openssl版本不匹配，因环境问题无法升级openssl版本，所以可以进行如下修改：
因为python 2.7.5有的版本（或更高版本）增加了certificate verification，正是因为这个特性导致ambari-agent无法连接server。
解决方法：
修改/etc/python/cert-verification.cfg配置文件：
# vim /etc/python/cert-verification.cfg
[https]
verify=disable
修改为verify=disable，就可以正常注册。
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还是失败的话
1、vim /etc/ambari-agent/conf/ambari-agent.ini
查看hostname是否改成本机的主机名；
输入hostname即可知道自己主机的hostname
2、中文和英文操作系统版本问题，中文操作系统出错，英文则成功；
centos6：
修改vim /etc/sysconfig/i18n
LANG="en_US.UTF-8"
SYSFONT="latarcyrheb-sun16"
centos7：
修改vim /etc/locale.conf
LANG="en_US.UTF-8"
LANGUAGE="en_US:en"
---------------------
datanode无法启动
手动启动
/usr/hdp/2.4.0.0-169/hadoop-hdfs/bin/hdfs --config /usr/hdp/current/hadoop-client/conf datanode
19/02/21 13:18:32 FATAL datanode.DataNode: Exception in secureMain
java.lang.ExceptionInInitializerError
at javax.crypto.KeyGenerator.nextSpi(KeyGenerator.java:340)
at javax.crypto.KeyGenerator.<init>(KeyGenerator.java:168)
at javax.crypto.KeyGenerator.getInstance(KeyGenerator.java:223)
at org.apache.hadoop.security.token.SecretManager.<init>(SecretManager.java:143)
at org.apache.hadoop.hdfs.security.token.block.BlockPoolTokenSecretManager.<init>(BlockPoolTokenSecretManager.java:36)
at org.apache.hadoop.hdfs.server.datanode.DataNode.startDataNode(DataNode.java:1148)
at org.apache.hadoop.hdfs.server.datanode.DataNode.<init>(DataNode.java:429)
at org.apache.hadoop.hdfs.server.datanode.DataNode.makeInstance(DataNode.java:2414)
at org.apache.hadoop.hdfs.server.datanode.DataNode.instantiateDataNode(DataNode.java:2301)
at org.apache.hadoop.hdfs.server.datanode.DataNode.createDataNode(DataNode.java:2348)
at org.apache.hadoop.hdfs.server.datanode.DataNode.secureMain(DataNode.java:2530)
at org.apache.hadoop.hdfs.server.datanode.DataNode.main(DataNode.java:2554)
Caused by: java.lang.SecurityException: Can not initialize cryptographic mechanism
at javax.crypto.JceSecurity.<clinit>(JceSecurity.java:93)
... 12 more
Caused by: java.lang.SecurityException: Cannot locate policy or framework files!
at javax.crypto.JceSecurity.setupJurisdictionPolicies(JceSecurity.java:316)
at javax.crypto.JceSecurity.access$000(JceSecurity.java:50)
at javax.crypto.JceSecurity$1.run(JceSecurity.java:85)
at java.security.AccessController.doPrivileged(Native Method)
at javax.crypto.JceSecurity.<clinit>(JceSecurity.java:82)
... 12 more
19/02/21 13:18:32 INFO util.ExitUtil: Exiting with status 1
jce 版本不对
https://blog.csdn.net/zero__007/article/details/80947247
java8的在http://www.oracle.com/technetwork/java/javase/downloads/jce8-download-2133166.html
解压后有三个文件：
README.txt
local_policy.jar
US_export_policy.jar 看README.txt就了解怎么用了,我是将<JAVA_HOME> /jre/lib/security/policy/unlimited里的两个文件替换 。
