環境：
主機sam02安裝hive,主機sam03安裝mysql
當主機sam02用hive嘗試連接主機sam03的客戶端mysql時，出現以下錯誤
[root@sam02 conf]# schematool --initSchema -dbType mysql
which: no hbase in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/usr/local/jdk:/usr/local/jdk/bin:/usr/local/hadoop/bin:/usr/local/hadoop/sbin:/usr/local/zookeeper/bin:/usr/local/flume/bin:/root/bin:/usr/local/jdk:/usr/local/jdk/bin:/usr/local/hadoop/bin:/usr/local/hadoop/sbin:/usr/local/zookeeper/bin:/usr/local/flume/bin:/usr/local/hive/bin)
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/usr/local/hive/lib/log4j-slf4j-impl-2.4.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/usr/local/hadoop/share/hadoop/common/lib/slf4j-log4j12-1.7.10.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.apache.logging.slf4j.Log4jLoggerFactory]
Metastore connection URL: jdbc:mysql://sam03:3306/hive?createDatabaseIfNotExist=true
Metastore Connection Driver : com.mysql.jdbc.Driver
Metastore connection User: root
org.apache.hadoop.hive.metastore.HiveMetaException: Failed to get schema version.
Underlying cause: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException : Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
SQL Error code: 0
Use --verbose for detailed stacktrace.
*** schemaTool failed ***
網上說是因為waittime_out的問題，按照網上所說修改后bug還是復現；
后面嘗試在安裝了hive的主機上連接自身的mysql，發現連接成功說明不是waittime_out的問題，最后發現是因為防火牆沒有關閉，關閉了防火牆就解決了。
解決方法：關閉主機sam03的防火牆
systemctl stop firewalld