Using Docker [读书笔记] 2

Dockerfile 中的 EXEC VS SHELL 形式
Several instructions (RUN, CMD and ENTRYPOINT), take both a shell format and an exec format. The exec form takes a JSON array (e.g. ["executable", "param1", "param2"]) which assumes the first item is the name of an executable which is then executed with the remaining items as parameters. The shell format is a freeform string which will be interpreted by passing to /bin/sh -c. Use the exec form to avoid the shell munging strings or in cases where the image doesn’t have /bin/sh.

FROM base image
ADD 从远程或本地Context copy到image, 如果是压缩文件, 会自动解压. 最好不要用ADD, 用COPY 或 RUN wget/curl;
CMD 当Container启动完, 执行的命令. 后边的CMD 会覆盖前面的CMD;
COPY 有EXEC 和 SHELL 格式, EXEC 的json 格式支持路径中有空格, 支持Wildcard, 但不支持到Context的上层目录;
ENV 设置环境变量
RUN run 给定的脚本, 并commit 其结果
USER 设置用户, 用以给后续的CMD, RUN, COPY, ENTRYPOINT 等用; host 和Container 之间的userId是一样的, user name 可能不一样.
EXPOSE 标明要监听的端口, 用以告诉docker server.
ENTRYPOINT Container 启动后默认执行的脚本, 可能被CMD 或 docker run的命令覆盖.
ONBUILD 如果本image 被用作base image, 那么后续build 时候要执行的脚本
VOLUME 设置要挂载的文件

Docker links are the simplest way to allow containers on the same host to talk to each other. Using Docker links will also add the alias and the link container ID to /etc/hosts on the master container, allowing the link container to be addressed by name from the master container.By default, containers will be able to talk to each other whether not they have been explicitly linked. Perhaps most significantly they are static — links aren’t updated if the link container goes down or is replaced. Also, the link container must be started before the master container, meaning you can’t have bidirectional links.

Volumes are directories[18] that are not part of the container’s UFS, they are just normal directories on the host that are bind mounted into the container.

通过Dockerfile的 VOLUME命令, 不能指定host的文件路径, 所以都是动态指定的, 所以可以通过 docker inspect -f {{.Volumes}} ${containerId} 查看
通过docker run -v hostDir:containerDir 指定路径.

通过 --volumes-from CONTAINER shared volume 即使原container 没有在run, 照样可以使用这个volume.

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