• ubuntu 安装jdk 1.8
  • 下载
  • 安装
  • 问题

ubuntu 安装jdk 1.8

文档编写时间：2021/07/14

zhanghe@test:~$ whoami
zhanghe
zhanghe@test:~$ date
Wed Jul 14 12:45:21 UTC 2021
zhanghe@test:~$ cat /proc/version
Linux version 4.15.0-112-generic (buildd@lcy01-amd64-027) (gcc version 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)) #113-Ubuntu SMP Thu Jul 9 23:41:39 UTC 2020
zhanghe@test:~$ uname -a
Linux test 4.15.0-112-generic #113-Ubuntu SMP Thu Jul 9 23:41:39 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

下载

https://www.oracle.com/java/technologies/javase/javase-jdk8-downloads.html

下载东西需要注册账号，这一点有点上火，下载完之后文件名是jdk-8u291-linux-x64.tar.gz

安装

sudo su
root@test:/home/zhanghe# tar -zxvf jdk-8u291-linux-x64.tar.gz 
root@test:/home/zhanghe# mv jdk1.8.0_291 /usr/local/jdk1.8
root@test:/home/zhanghe# ls /usr/local/jdk1.8
bin  COPYRIGHT  include  javafx-src.zip  jmc.txt  jre  legal  lib  LICENSE  man  README.html  release  src.zip  THIRDPARTYLICENSEREADME-JAVAFX.txt  THIRDPARTYLICENSEREADME.txt

vim /etc/profile 
export JAVA_HOME=/usr/local/jdk1.8
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=.:${JAVA_HOME}/bin:$PATH

root@test:/home/zhanghe# source /etc/profile
root@test:/home/zhanghe# java -version
java version "1.8.0_291"
Java(TM) SE Runtime Environment (build 1.8.0_291-b10)
Java HotSpot(TM) 64-Bit Server VM (build 25.291-b10, mixed mode)

问题

这个安装太简单，但是后续会遇到一些问题，那我现在从root退出到普通用户以后，发现jdk就不能用了，哪怕再进入root也不能用了，如下所示，这是怎么回事？其实重启就好了，但是不重启怎么办呢？

root@test:/home/zhanghe# java -version

Command 'java' not found, but can be installed with:

apt install default-jre            
apt install openjdk-11-jre-headless
apt install openjdk-8-jre-headless 

root@test:/home/zhanghe# source /etc/profile
root@test:/home/zhanghe# java -version
java version "1.8.0_291"
Java(TM) SE Runtime Environment (build 1.8.0_291-b10)
Java HotSpot(TM) 64-Bit Server VM (build 25.291-b10, mixed mode)
root@test:/home/zhanghe# exit
exit
zhanghe@test:~$ sudo su
root@test:/home/zhanghe# java -version

Command 'java' not found, but can be installed with:

apt install default-jre            
apt install openjdk-11-jre-headless
apt install openjdk-8-jre-headless 

解决方法，我们不要用sudo su来切换用户，而要用sudo su - 来切换，这样就会切换用户时读取/etc/profile文件，如下所示：

zhanghe@test:~$ sudo su
root@test:/home/zhanghe# exit
exit
zhanghe@test:~$ sudo su -
root@test:~# java -version
java version "1.8.0_291"
Java(TM) SE Runtime Environment (build 1.8.0_291-b10)
Java HotSpot(TM) 64-Bit Server VM (build 25.291-b10, mixed mode)