docker build过程安装mysql， 到mysql密码设置部分卡死了，为何会这样？怎么办？

Unpacking libklibc (2.0.4-8ubuntu1.16.04.2) ...
Selecting previously unselected package klibc-utils.
Preparing to unpack .../klibc-utils_2.0.4-8ubuntu1.16.04.2_amd64.deb ...
Adding 'persion of /usr/share/initramfs-tools/hooks/klibc to /usr/share/initramfs-tools/hooks/klibc^i-t by klibc-utils'
Unpacking klibc-utils (2.0.4-8ubuntu1.16.04.2) ...

While not mandatory, it is highly recommended that you set a password for the
MySQL administrative "root" user.

If this field is left blank, the password will not be changed.

New password for the MySQL "root" user: root

然后就卡死了，很久：（
Ctrl+C 所有下载和镜像都报废的样子,累...