## 基本結構 Dockerfile 由一行行命令語句組成，并且支持以 `#` 開頭的注釋行。 一般的，Dockerfile 分為四部分：基礎鏡像信息、維護者信息、鏡像操作指令和容器啟動時執行指令。 例如 ``` # This dockerfile uses the ubuntu image # VERSION 2 - EDITION 1 # Author: docker_user # Command format: Instruction [arguments / command] .. # Base image to use, this must be set as the first line FROM ubuntu # Maintainer: docker_user <docker_user at email.com> (@docker_user) MAINTAINER docker_user docker_user@email.com # Commands to update the image RUN echo "deb http://archive.ubuntu.com/ubuntu/ raring main universe" >> /etc/apt/sources.list RUN apt-get update && apt-get install -y nginx RUN echo "\ndaemon off;" >> /etc/nginx/nginx.conf # Commands when creating a new container CMD /usr/sbin/nginx ``` 其中，一開始必須指明所基于的鏡像名稱，接下來推薦說明維護者信息。 后面則是鏡像操作指令，例如 `RUN` 指令，`RUN` 指令將對鏡像執行跟隨的命令。每運行一條 `RUN` 指令，鏡像添加新的一層，并提交。 最后是 `CMD` 指令，來指定運行容器時的操作命令。 下面是一個更復雜的例子 ``` # Nginx # # VERSION 0.0.1 FROM ubuntu MAINTAINER Victor Vieux <victor@docker.com> RUN apt-get update && apt-get install -y inotify-tools nginx apache2 openssh-server # Firefox over VNC # # VERSION 0.3 FROM ubuntu # Install vnc, xvfb in order to create a 'fake' display and firefox RUN apt-get update && apt-get install -y x11vnc xvfb firefox RUN mkdir /.vnc # Setup a password RUN x11vnc -storepasswd 1234 ~/.vnc/passwd # Autostart firefox (might not be the best way, but it does the trick) RUN bash -c 'echo "firefox" >> /.bashrc' EXPOSE 5900 CMD ["x11vnc", "-forever", "-usepw", "-create"] # Multiple images example # # VERSION 0.1 FROM ubuntu RUN echo foo > bar # Will output something like ===> 907ad6c2736f FROM ubuntu RUN echo moo > oink # Will output something like ===> 695d7793cbe4 # You?ll now have two images, 907ad6c2736f with /bar, and 695d7793cbe4 with # /oink. ```