docker内apt-get install提示权限不足

E: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied)
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?

只需要进入docker时使用root用户就可以了
docker exec -it --user root /bin/bash
这样进入是不要密码的，进入之后执行下面两个命令就好了

apt-get  update
apt-get install xx #xx为你安装的东西