# CentOS下手动安装JDK,Python环境和界面切换

## CentOS7图形界面与命令行界面切换

1. 在图形界面使用 `Ctrl+Alt+F2` 切换到dos界面
2. dos界面 `Ctrl+Alt+F2` 切换回图形界面
3. 在命令上,输入 `init 3` 命令切换到dos界面
4. 输入 `init 5` 命令切换到图形界面

**如果想系统默认以某种方式启动,使用systemd创建符号链接指向默认运行级别。** 修改方法为: 首先删除已经存在的符号链接:

```
rm /etc/systemd/system/default.target
```

默认级别转换为3(文本模式):

```
ln -sf /lib/systemd/system/multi-user.target /etc/systemdsystem/default.target
```

或者默认级别转换为5(图形模式):

```
ln -sf /lib/systemd/system/graphical.target /etc/systemdsystem/default.target
```

重启:

```
reboot
```

## Centos7手动安装JDK以及环境配置

云服务器的SSH登录(建议Xshell),安装必要程序后

依次运行命令:

```
mkdir /usr/java
wget https://download.oracle.com/otn-pub/java/jdk/13.0.2+8/d4173c853231432d94f001e99d882ca7/jdk-13.0.2_linux-x64_bin.tar.gz
tar zxvf jdk-13.0.2_linux-x64_bin.tar.gz
rm -f jdk-13.0.2_linux-x64_bin.tar.gz
vim /etc/profile # 或者 vi /etc/profile
```

末尾添加并保存

```
export JAVA_HOME=/usr/java/jdk1.8.0_152
export CLASSPATH=.:$JAVA_HOME/jre/lib/rt.jar:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
export PATH=$PATH:$JAVA_HOME/bin
```

最后使修改生效

```
source /etc/profile
```

测试命令

```
java -version
```

## CentOS7 下 Python3 的编译安装

配置好yum源: 安装好前置依赖

```
yum -y install gcc python-setuptools.noarch bash-compleetion-extras.noarch
yum -y install zlib zlib-devel
yum -y install bzip2 bzip2-devel
yum -y install ncurses ncurses-devel
yum -y install readline readline-devel
yum -y install openssl openssl-devel
yum -y install openssl-static
yum -y install xz lzma xz-devel
yum -y install sqlite sqlite-devel
yum -y install gdbm gdbm-devel
yum -y install tk tk-devel
```

或者

```
yum install gcc python-setuptools.noarch bash-compleetion-extras.noarch \
            zlib zlib-devel bzip2 bzip2-devel ncurses ncurses-devel readline readline-devel \
            openssl openssl-devel openssl-static xz lzma xz-devel sqlite sqlite-devel gdbm gdbm-devel \
            tk tk-devel gcc-c++ make imake cmake automake glibc glibc-devel glib2 libxml glib2-devel \
            libxml2 libxml2-devel libmcrypt libmcrypt-devel postgresql-devel
```

### 使用源码进行编译安装

官网下载源码包

```
wget https://www.python.org/ftp/python/3.8.1/Python-3.8.1.tgz
```

解压

```
xz Python-3.8.1.tar.gz
tar -xvzf Python-3.8.1.tgz
```

进入目录:配置安装目录,如果没有目标目录需要提前创建

```
./configure --prefix=/usr/local/python3 --enable-optimizations --enable-shared --enable-optimizations　
# 不配置也可以,直接./configure命令

# --prefix：指定安装路径
# --enable-shared：禁用/启用构建共享python库
# --enable-optimizations：启用昂贵,稳定的优化（PGO等）。默认情况下禁用。
# 安装时善用 ./configure --help 这个功能..
```

编译,安装

```
make && make install
```

修改Python共享库

```
vim /etc/ld.so.conf.d/python3.conf
```

在/etc/ld.so.conf.d/python3.conf文件中添加以下内容:

```
/usr/local/python3/lib/
```

刷新动态链


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