參考https://www.cnblogs.com/xing901022/p/3895719.html
先看報錯信息：
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1521)))
TNS-12541: TNS:no listener
TNS-12560: TNS:protocol adapter error
TNS-00511: No listener
Linux Error: 111: Connection refused
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))
TNS-12541: TNS:no listener
TNS-12560: TNS:protocol adapter error
TNS-00511: No listener
Linux Error: 111: Connection refused
原因：
查看主機名，發現/etc/hosts內localhost只想多個地址，引發監聽沖突
[root@localhost ~]# cat /etc/hosts
127.0.0.1 localhost.domain localhost
10.4.40.70 localhost
解決方法：
修改主機名：
hostname
hostname oracle
/etc/hosts
127.0.0.1 localhost localhost.domain
192.168.0.1 oracle
/etc/sysconfig/network
hostname = oracle
再次啟動,成功