cloudera-scm-server 宕机后重启，报错，日志如下：
2017-12-05 12:51:11,920 WARN com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1:com.mchange.v2.resourcepool.BasicResourcePool: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1254ff50 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (5). Last acquisition attempt exception:
org.postgresql.util.PSQLException: Connection refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:136)
at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:66)
at org.postgresql.jdbc2.AbstractJdbc2Connection.(AbstractJdbc2Connection.java:125)
at org.postgresql.jdbc3.AbstractJdbc3Connection.(AbstractJdbc3Connection.java:30)
at org.postgresql.jdbc3g.AbstractJdbc3gConnection.(AbstractJdbc3gConnection.java:22)
at org.postgresql.jdbc4.AbstractJdbc4Connection.(AbstractJdbc4Connection.java:30)
at org.postgresql.jdbc4.Jdbc4Connection.(Jdbc4Connection.java:24)
at org.postgresql.Driver.makeConnection(Driver.java:393)
at org.postgresql.Driver.connect(Driver.java:267)
at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)
at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
Caused by: java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:579)
at java.net.Socket.connect(Socket.java:528)
at java.net.Socket.(Socket.java:425)
at java.net.Socket.(Socket.java:208)
at org.postgresql.core.PGStream.(PGStream.java:62)
at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:76)
... 16 more
因为cloudera使用了postgresql，没有启动cloudera-scm-server-db，所以启动cloudera-scm-server-db，然后继续报错，日志如下：
LOG: could not bind IPv4 socket: Permission denied
HINT: Is another postmaster already running on port 7432? If not, wait a few seconds and retry.
LOG: could not bind IPv6 socket: Permission denied
HINT: Is another postmaster already running on port 7432? If not, wait a few seconds and retry.
WARNING: could not create listen socket for "*"
FATAL: could not create any TCP/IP sockets
LOG: could not bind IPv4 socket: Permission denied
HINT: Is another postmaster already running on port 7432? If not, wait a few seconds and retry.
LOG: could not bind IPv6 socket: Permission denied
HINT: Is another postmaster already running on port 7432? If not, wait a few seconds and retry.
WARNING: could not create listen socket for "*"
FATAL: could not create any TCP/IP sockets
查看7432端口并没用被占用，最后发现是selinux开启了，导致 could not create listen socket for "*" ，关闭selinux即可