一 安装JDK

1.下载JDK

目前最新JDK：Java SE Development Kit 8u91
http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html


2.解压安装
我们把JDK安装到这个路径：/usr/lib/jvm
如果没有这个目录（第一次当然没有），我们就新建一个目录
1 cd /usr/lib
2 sudo mkdir jvm
建立好了以后，我们来到刚才下载好的压缩包的目录，解压到我们刚才新建的文件夹里面去，并且修改好名字方便我们管理
1 sudo tar zxvf ./jdk-8u91-linux-x64.tar.gz  -C /usr/lib/jvm
2 cd /usr/lib/jvm
3 sudo mv jdk1.8.0_91/   jdk8

3.配置环境变量
gedit ~/.bashrc
在打开的文件的末尾添加
export JAVA_HOME=/usr/lib/jvm/jdk8
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=${JAVA_HOME}/bin:$PATH
保存退出，然后输入下面的命令来使之生效
source ~/.bashrc

4.配置默认JDK(一般情况下这一步都可以省略)
由于一些Linux的发行版中已经存在默认的JDK，如OpenJDK等。所以为了使得我们刚才安装好的JDK版本能成为默认的JDK版本，我们还要进行下面的配置。
执行下面的命令：

sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk8/bin/java 300
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk8/bin/javac 300
 注意：如果以上两个命令出现找不到路径问题，只要重启一下计算机在重复上面两行代码就OK了。
 
5.验证安装成功
michael@ubuntu:~$ java -version
java version "1.8.0_91"
Java(TM) SE Runtime Environment (build 1.8.0_91-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.91-b14, mixed mode)

二 配置SSH

michael@ubuntu:~$ sudo apt-get install ssh
[sudo] password for michael: 
michael@ubuntu:~$ ls -a /home/michael
.              .dmrc             .local             .python-eggs
..             Documents         .mission-control   redis-3.2.0
.bash_history  Downloads         .mozilla           redis-3.2.0.tar.gz
.bash_logout   examples.desktop  Music              .rediscli_history
.bashrc        ez_setup.py       .oracle_jre_usage  Templates
.bashrc~       .fontconfig       .pam_environment   .thumbnails
.cache         .gconf            Pictures           Videos
.compiz-1      .gnome2           .profile           .Xauthority
.config        .gtk-bookmarks    Public             .xsession-errors
.dbus          .gvfs             .pulse             .xsession-errors.old
Desktop        .ICEauthority     .pulse-cookie
michael@ubuntu:~$ cd .ssh
bash: cd: .ssh: No such file or directory
michael@ubuntu:~$ ssh-keygen -t dsa -P '' -f ~/.ssh/id_dsa

Generating public/private dsa key pair.
Created directory '/home/michael/.ssh'.
Your identification has been saved in /home/michael/.ssh/id_dsa.
Your public key has been saved in /home/michael/.ssh/id_dsa.pub.
The key fingerprint is:
a8:c1:14:50:51:a8:4f:51:05:92:fe:b3:f0:1c:be:71 michael@ubuntu
The key's randomart image is:
+--[ DSA 1024]----+
|  .o=*+o.        |
|    +o           |
|   o..           |
|  .oo  .         |
|   oo.. S        |
|    oo+          |
|    .=.+E        |
|      =o         |
|      ..         |
+-----------------+
michael@ubuntu:~$ cat ~/.ssh/id_dsa.pub >>~/.ssh/authorized_keys
michael@ubuntu:~$ ssh -version
OpenSSH_5.9p1 Debian-5ubuntu1.9, OpenSSL 1.0.1 14 Mar 2012
Bad escape character 'rsion'.
michael@ubuntu:~$ ssh localhost
The authenticity of host 'localhost (127.0.0.1)' can't be established.
ECDSA key fingerprint is b7:fe:dc:32:13:c0:d6:2f:20:1b:ea:c8:ab:ab:c6:55.
Are you sure you want to continue connecting (yes/no)? y
Please type 'yes' or 'no': yes
Warning: Permanently added 'localhost' (ECDSA) to the list of known hosts.
Welcome to Ubuntu 12.04.1 LTS (GNU/Linux 3.2.0-29-generic x86_64)

 * Documentation:  https://help.ubuntu.com/

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Last login: Tue May 24 07:20:17 2016