在我的Dockerfile我有一句话：
RUN apt-get -qq update && apt-get install -y -qq --no-install-recommends vim
Docker在构建容器映像时运行它：
$ docker build .
Sending build context to Docker daemon 31.74 kB
Step 1 : FROM node
---> 2647b0da972f
Step 2 : MAINTAINER jillix <support@jillix.com>
---> Using cache
---> 06aad06901af
Step 3 : ENV DEBIAN_FRONTEND noninteractive
---> Using cache
---> d4f2c77d2fa1
Step 4 : RUN apt-get -qq update && apt-get install -y -qq --no-install-recommends vim
---> Running in 263680fcd78f
debconf: delaying package configuration, since apt-utils is not installed
Selecting previously unselected package libgpm2:amd64.
(Reading database ... 21065 files and directories currently installed.)
Preparing to unpack .../libgpm2_1.20.4-6.1+b2_amd64.deb ...
Unpacking libgpm2:amd64 (1.20.4-6.1+b2) ...
Selecting previously unselected package vim-common.
Preparing to unpack .../vim-common_2%3a7.4.488-7_amd64.deb ...
Unpacking vim-common (2:7.4.488-7) ...
Selecting previously unselected package vim-runtime.
Preparing to unpack .../vim-runtime_2%3a7.4.488-7_all.deb ...
Adding 'diversion of /usr/share/vim/vim74/doc/help.txt to /usr/share/vim/vim74/doc/help.txt.vim-tiny by vim-runtime'
Adding 'diversion of /usr/share/vim/vim74/doc/tags to /usr/share/vim/vim74/doc/tags.vim-tiny by vim-runtime'
Unpacking vim-runtime (2:7.4.488-7) ...
Selecting previously unselected package vim.
Preparing to unpack .../vim_2%3a7.4.488-7_amd64.deb ...
Unpacking vim (2:7.4.488-7) ...
Processing triggers for mime-support (3.58) ...
Processing triggers for hicolor-icon-theme (0.13-1) ...
Setting up libgpm2:amd64 (1.20.4-6.1+b2) ...
Setting up vim-common (2:7.4.488-7) ...
Setting up vim-runtime (2:7.4.488-7) ...
Processing /usr/share/vim/addons/doc
Setting up vim (2:7.4.488-7) ...
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/vim (vim) in auto mode
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/vimdiff (vimdiff) in auto mode
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/rvim (rvim) in auto mode
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/rview (rview) in auto mode
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/vi (vi) in auto mode
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/view (view) in auto mode
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/ex (ex) in auto mode
update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/editor (editor) in auto mode
Processing triggers for libc-bin (2.19-18+deb8u1) ...
---> 0b46f93ada63
...
但是当我运行我的容器时，没有安装vim：
root@db969727026f:/app# vim
bash: vim: command not found
如果我在容器中运行相同的apt-get命令，则会安装vim（这也告诉我Docker没有）。
我做错了什么？还是Docker？