以下Dockerfile为何build不了？问题出在哪里？
FROM ubuntu
LABEL Description="test" Vender="test" Version="1.0"
RUN apt-get update && apt-get install -y git gcc g++ tmux apt-utils mysql-client mysql-server
docker build -t test/test .
卡在下面这里了，等多久没没用，为何会这样呢？
上面Dockerfile问题出在哪里呢？
Selecting previously unselected package psmisc.
Preparing to unpack .../psmisc_22.21-2.1build1_amd64.deb ...
Unpacking psmisc (22.21-2.1build1) ...
Processing triggers for systemd (229-4ubuntu6) ...
Processing triggers for libc-bin (2.23-0ubuntu3) ...
Setting up mysql-common (5.7.16-0ubuntu0.16.04.1) ...
update-alternatives: using /etc/mysql/my.cnf.fallback to provide /etc/mysql/my.cnf (my.cnf) in auto mode
Selecting previously unselected package mysql-server-5.7.
(Reading database ... 10999 files and directories currently installed.)
Preparing to unpack .../mysql-server-5.7_5.7.16-0ubuntu0.16.04.1_amd64.deb ...
debconf: unable to initialize frontend: Dialog
debconf: (TERM is not set, so the dialog frontend is not usable.)
debconf: falling back to frontend: Readline
Configuring mysql-server-5.7
----------------------------
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: 
