centos7和centos6通過yum安裝JDK1.8
查看JDK的安裝路徑
# java -version
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查看Linux系統版本信息
# cat /etc/redhat-release
CentOS release 6.9 (Final)
[root@li409-225 ~]# cat /etc/issue
CentOS release 6.9 (Final)
Kernel \r on an \m
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centos6或centos7都可用的 yum安裝jdk
安裝之前先檢查一下系統有沒有自帶open-jdk
命令：
rpm -qa |grep java
rpm -qa |grep jdk
rpm -qa |grep gcj
如果沒有輸入信息表示沒有安裝。
如果安裝可以使用
rpm -qa | grep java | xargs rpm -e --nodeps
批量卸載所有帶有Java的文件 這句命令的關鍵字是java
檢索包含java的列表（可跳過此步）：
yum list java*
檢索1.8的列表：
yum list java-1.8*
安裝1.8.0的所有文件：
yum install java-1.8.0-openjdk* -y
出現 Complete!表示安裝完成
使用命令檢查是否安裝成功：
#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)
不需要對path進行手動設置，已自動設置好了
yum install 了之后，java 是默認下載到 /usr/lib/jvm/ 這個目錄下。
# find / -name 'java'
/var/lib/alternatives/java
/etc/pki/ca-trust/extracted/java
/etc/pki/java
/etc/alternatives/java
/etc/java
/root/sphinx-for-chinese-2.2.1-dev-r4311/api/java
/usr/share/javadoc/java-1.8.0-openjdk-1.8.0.161-3.b14.el6_9/jre/api/plugin/dom/com/sun/java
/usr/share/javadoc/java-1.8.0-openjdk-1.8.0.161-3.b14.el6_9/jre/api/accessibility/jaccess/spec/com/sun/java
/usr/share/javadoc/java-1.8.0-openjdk-1.8.0.161-3.b14.el6_9/api/org/omg/stub/java
/usr/share/javadoc/java-1.8.0-openjdk-1.8.0.161-3.b14.el6_9/api/java
/usr/share/javadoc/java-1.8.0-openjdk-1.8.0.161-3.b14.el6_9-debug/jre/api/plugin/dom/com/sun/java
/usr/share/javadoc/java-1.8.0-openjdk-1.8.0.161-3.b14.el6_9-debug/jre/api/accessibility/jaccess/spec/com/sun/java
/usr/share/javadoc/java-1.8.0-openjdk-1.8.0.161-3.b14.el6_9-debug/api/org/omg/stub/java
/usr/share/javadoc/java-1.8.0-openjdk-1.8.0.161-3.b14.el6_9-debug/api/java
/usr/share/javadoc/java
/usr/share/doc/db4-devel-4.7.25/ref/java
/usr/share/doc/db4-devel-4.7.25/java
/usr/share/java
/usr/bin/java
/usr/lib/jvm-exports/java
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.161-3.b14.el6_9.x86_64-debug/jre/bin/java
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.161-3.b14.el6_9.x86_64-debug/bin/java
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.161-3.b14.el6_9.x86_64/jre/bin/java
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.161-3.b14.el6_9.x86_64/bin/java
/usr/lib/jvm/java
/usr/lib/java
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其中啟動命令需要用到的兩個是：
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.161-3.b14.el6_9.x86_64/bin/java
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.161-3.b14.el6_9.x86_64/jre/lib/ext
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