版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/lzxlfly/article/details/83388374
一、防火墙
CentOS7默认用firewall作为防火墙，不同于CentOS6用iptables
查看防火墙状态
firewall-cmd --state启动防火墙
systemctl start firewalld.service关闭防火墙
systemctl stop firewalld.service开机启动
systemctl enable firewalld.service #开机自启
systemctl disable firewalld.service #开机不自启重新加载配置
firewall-cmd --reload查看开放端口
firewall-cmd --zone=public --list-ports添加开放端口
firewall-cmd --zone=public --add-port=80/tcp --permanent 移除开放端口
firewall-cmd --zone= public --remove-port=80/tcp --permanent二、自带jdk
装jdk时候发现系统有了个openjdk，上网查看才知道centos7一般自带的jdk，不是oracle官方的，所以要把它卸载掉
[root@localhost home]# java -version
openjdk version "1.8.0_161"
OpenJDK Runtime Environment (build 1.8.0_161-b14)
OpenJDK 64-Bit Server VM (build 25.161-b14, mixed mode)首先查看具体有哪些 jdk
[root@localhost home]# rpm -qa | grep java
python-javapackages-3.4.1-11.el7.noarch
java-1.8.0-openjdk-headless-1.8.0.161-2.b14.el7.x86_64
tzdata-java-2018c-1.el7.noarch
java-1.7.0-openjdk-1.7.0.171-2.6.13.2.el7.x86_64
java-1.8.0-openjdk-1.8.0.161-2.b14.el7.x86_64
javapackages-tools-3.4.1-11.el7.noarch
java-1.7.0-openjdk-headless-1.7.0.171-2.6.13.2.el7.x86_64看到openjdk 1.7、1.8都有，接下来把他们卸载掉，也可以按文件名逐个卸载
[root@localhost home]# rpm -e --nodeps java*openjdk*从新查看是否卸载
[root@localhost home]# rpm -qa | grep java
python-javapackages-3.4.1-11.el7.noarch
tzdata-java-2018c-1.el7.noarch
javapackages-tools-3.4.1-11.el7.noarch接下来安装oracle官方的jdk
[root@localhost home]# rpm -ivh jdk-8u181-linux-x64.rpm
warning: jdk-8u181-linux-x64.rpm: Header V3 RSA/SHA256 Signature, key ID ec551f03: NOKEY
Preparing... ################################# [100%]
Updating / installing...
1:jdk1.8-2000:1.8.0_181-fcs ################################# [100%]
Unpacking JAR files...
tools.jar...
plugin.jar...
javaws.jar...
deploy.jar...
rt.jar...
jsse.jar...
charsets.jar...
localedata.jar...查看自己安装的jdk
[root@localhost home]#java -version
java version "1.8.0_181"
Java(TM) SE Runtime Environment (build 1.8.0_181-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.181-b13, mixed mode)