centos7/8安装java和mysql

一、java的安装
1.首先查看是否已安装

[root@localhost ~]# java -version

2.自带jdk

rpm -qa |grep java

rpm -qa |grep jdk
rpm -qa |grep gcj
3.卸载系统自带

rpm -qa | grep java | xargs rpm -e --nodeps

4.卸载yum安装

yum -y remove java-1.8.0-openjdk-headless.x86_64

5.安装jdk

yum list java-1.8*

yum install java-1.8.0-openjdk* -y

验证：java -version



二、mysql的安装
1.下载

wget -i -c http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm

2.安装
yum -y install mysql57-community-release-el7-10.noarch.rpm

3.0公钥尚未安装

　　rpm --import https://repo.mysql.com/RPM-GPG-KEY-mysql-2022

3.1安装服务

yum -y install mysql-community-server

　　

4.启动mysql

systemctl start  mysqld.service
5.查看运行状态

systemctl status mysqld.service
6.mysql的root密码

grep "password" /var/log/mysqld.log
7.进入mysql

mysql -uroot -p
8.修改mysqlroot密码

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'new password';

linux中mysql密码忘记怎么办？
a.找到/etc/my.cnf文件，[mysqld]下增加：skip-grant-tables
b.重启mysql服务：systemctl start  mysqld.service
c.
　　use mysql;    
　　update mysql.user set authentication_string=password('newpassword') where user='root';
　　flush privileges;
　　exit
d.重启mysql服务
访问不到mysql怎么办？：is not allowed to connect to this MySQL server
　　a.use mysql;
　　b.select t.host from user t where t.user = 'root';
　　c.update user set host = ‘%’ where user = ‘root’;//报错没事  不用管
　　d.flush privileges;
　　e.测试连接

9.下载yum自动更新mysql

yum -y remove mysql57-community-release-el7-10.noarch

三、直接安装jre
1.下载：百度java，在官网下载rpm包
2.进入文件路径执行：yum localinstall jre-8u301-linux-x64.rpm

localinstall安装命令