| 方法一执行systemctl get-default 可以查看当前启动界面root@fenglg-PC:/etc/pam.d# systemctl get-default graphical.target
 切换默认切换字符界面fenglg@fenglg-PC:~$ sudo systemctl set-default multi-user.target
 Removed /etc/systemd/system/default.target.
 Created symlink /etc/systemd/system/default.target → /lib/systemd/system/multi-user.target.
 确认修改结果出现如下软链接,说明修改成功Created symlink /etc/systemd/system/default.target → /lib/systemd/system/multi-user.target.
 
 也可以执行systemctl get-default 查看fenglg@fenglg-PC:/etc/systemd/system$ systemctl get-default multi-user.target
 修改为图形界面sudo systemctl set-default graphical.target
 
 执行结果如下:fenglg@fenglg-PC:/etc/systemd/system$ sudo systemctl set-default graphical.target Removed /etc/systemd/system/default.target.
 Created symlink /etc/systemd/system/default.target → /lib/systemd/system/graphical.target.
 
 再次查看fenglg@fenglg-PC:/etc/systemd/system$ systemctl get-default graphical.target
 每次切换后都可以再次重启,尝试登录切换后的界面,验证是否成功方法二
 可以手动创建软链接,如:sudo ln -svf  /lib/systemd/system/multi-user.target  /etc/systemd/system/default.target 
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