yum安装配置jdk

1、检查是否已安装JDK及卸载

以下命令二选一，中括号选一即可

yum list installed | grep [java][jdk]
rpm -qa | grep [java][jdk][gcj]

[[e-mail] ~]# yum list installed | grep java
Repodata is over 2 weeks old. Install yum-cron? Or run: yum makecache fast
java-1.7.0-openjdk.x86_64              1:1.7.0.111-2.6.7.8.el7         @anaconda
java-1.7.0-openjdk-headless.x86_64     1:1.7.0.111-2.6.7.8.el7         @anaconda
java-1.8.0-openjdk.x86_64              1:1.8.0.102-4.b14.el7           @anaconda
java-1.8.0-openjdk-headless.x86_64     1:1.8.0.102-4.b14.el7           @anaconda
javapackages-tools.noarch              3.4.1-11.el7                    @anaconda
python-javapackages.noarch             3.4.1-11.el7                    @anaconda
tzdata-java.noarch                     2016g-2.el7                     @anaconda

执行命令出现如上图所示，需要卸载，反之即不用

卸载JAVA环境：

yum -y remove java-1.6.0-openjdk*  //表时卸载所有openjdk相关文件输入
yum -y remove tzdata-java.noarch   //卸载tzdata-java

2、安装JDK

查看JDK软件包列表

yum search java | grep -i --color jdk

选择版本安装

yum install -y java-1.8.0-openjdk java-1.8.0-openjdk-devel
#或如下命令，安装jdk1.8.0的所有文件
yum install -y java-1.8.0-openjdk*

查看JDK是否安装成功

[[e-mail] ~]# java -version
openjdk version "1.8.0_252"
OpenJDK Runtime Environment (build 1.8.0_252-b09)
OpenJDK 64-Bit Server VM (build 25.252-b09, mixed mode)

3、配置环境变量

JDK默认安装路径/usr/lib/jvm

[[e-mail] ~]# ls /usr/lib/jvm
java                                             java-openjdk       jre-1.8.0-openjdk-1.8.0.252.b09-2.el7_8.x86_64
java-1.8.0                                       jre                jre-openjdk
java-1.8.0-openjdk                               jre-1.8.0
java-1.8.0-openjdk-1.8.0.252.b09-2.el7_8.x86_64  jre-1.8.0-openjdk

在/etc/profile文件添加如下命令

[[e-mail] ~]# vim /etc/profile
# set java environment  
JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.181-3.b13.el7_5.x86_64
PATH=$PATH:$JAVA_HOME/bin  
CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar  
export JAVA_HOME  CLASSPATH  PATH 

保存关闭profile文件，执行如下命令生效

[[e-mail] ~]# source  /etc/profile

使用如下命令，查看JDK变量

 echo $JAVA_HOME
 echo $PATH
 echo $CLASSPATH

[[e-mail] ~]#  echo $JAVA_HOME
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.181-3.b13.el7_5.x86_64
[[e-mail] ~]#  echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin:/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.181-3.b13.el7_5.x86_64/bin
[[e-mail] ~]#  echo $CLASSPATH
.:/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.181-3.b13.el7_5.x86_64/lib/dt.jar:/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.181-3.b13.el7_5.x86_64/lib/tools.jar