参考：https://blog.csdn.net/qq285744011/article/details/104299732

步骤

1. 查看PHP版本： php -v
2. sudo apt-get update

3. sudo apt-get install php7.4-gd

4. 提示已经成功：

   1.  
      Setting up php7.2-gd (7.2.24-0ubuntu0.18.04.2) ...
   2.  
      Creating config file /etc/php/7.2/mods-available/gd.ini with new version
   3.  
      Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
   4.  
      Processing triggers for libc-bin (2.27-3ubuntu1) ...
   5.  
      Processing triggers for libapache2-mod-php7.2 (7.2.24-0ubuntu0.18.04.2) ...

    

5. 重启apache： sudo apache2ctl restart

6. 完成