1、先下载对应的php-fpm镜像并启动，然后通过 exec登入对应的容器。
2、配置该容器的下载源
cp /etc/apt/sources.list /etc/apt/sources.copy.list # 备份原始下载源数据
echo "deb http://mirrors.ustc.edu.cn/debian stable main contrib non-free" > /etc/apt/sources.list
echo "deb-src http://mirrors.ustc.edu.cn/debian stable main contrib non-free" >> /etc/apt/sources.list
echo "deb http://mirrors.ustc.edu.cn/debian stable-proposed-updates main contrib non-free" >> /etc/apt/sources.list
echo "deb-src http://mirrors.ustc.edu.cn/debian stable-proposed-updates main contrib non-free" >> /etc/apt/sources.list
3、更新下载源、并下载必要的依赖
apt-get update
apt install -y libfreetype6 libwebp-dev libjpeg-dev libpng-dev
4、创建并初始化 /usr/src/php目录
docker-php-source extract
cd /usr/src/php/ext
5、配置 GD 扩展库并进行安装
docker-php-ext-configure gd --with-freetype-dir=/usr/include/ --with-jpeg-dir=/usr/include/ --with-png-dir=/usr/include
docker-php-ext-install gd
6、查看 GD扩展库是否安装成功
php -m | grep gd
7、重启容器
docker restart <容器 ID>
参考链接：
https://www.cnblogs.com/yesok/p/14268728.html
https://blog.csdn.net/weixin_39654823/article/details/111731555