经常需要对镜像内部的文件进行修改，例如在构建镜像时候修改配置文件。在使用一些开源镜像的过程中发现了一些对镜像文件进行的方式，这里以hadoop集群搭建和storm集群搭建为例介绍两种修改镜像内配置文件的方式。

一、通过context把配置文件传入镜像

step1. 在DockerFile同级目录下，创建conf文件夹，在文件夹中放置修改好的配置文件

step2. 在DockerFile中把conf中的配置文件放置到环境变量中

例：一个docker搭建hadoop集群的案例

文件夹结构

Dockerfile内容：

# # # # # # # # # # # # # # # # # # # # # # # # 

# Dockerfile to build hadoop container images #

# Based on Centos                             #

# # # # # # # # # # # # # # # # # # # # # # # #

#base image

FROM centos7-hadoop

# MainTainer

MAINTAINER neu_wj@163.com

#WORKDIR /root

# ssh without key

RUN ssh-keygen -t rsa -f ~/.ssh/id_rsa -P '' && \    cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys

#RUN ssh-keygen -q -t rsa -b 2048 -f /etc/ssh/ssh_host_rsa_key -N '' && \

#    ssh-keygen -q -t ecdsa -f /etc/ssh/ssh_host_ecdsa_key -N '' && \

#    ssh-keygen -t dsa -f /etc/ssh/ssh_host_ed25519_key  -N '' #RUN sed -i 's/UsePAM yes/UsePAM no/g' /etc/ssh/sshd_config

#RUN sed -i "s/#UsePrivilegeSeparation.*/UsePrivilegeSeparation no/g" /etc/ssh/sshd_config

COPY config/* /tmp/

RUN cat /tmp/ssh_config >> /etc/ssh/ssh_config && \

    mv /tmp/core-site.xml $HADOOP_HOME/etc/hadoop/core-site.xml && \

    mv /tmp/hdfs-site.xml $HADOOP_HOME/etc/hadoop/hdfs-site.xml && \

    mv /tmp/yarn-site.xml $HADOOP_HOME/etc/hadoop/yarn-site.xml && \

    mv /tmp/mapred-site.xml $HADOOP_HOME/etc/hadoop/mapred-site.xml && \

    mv /tmp/slaves $HADOOP_HOME/etc/hadoop/slaves

# SSH and SERF ports

EXPOSE 22 7373 7946

# HDFS ports

EXPOSE 50090 50475 50010

# YARN ports

#

#CMD ["/usr/sbin/sshd", "-D"]

#CMD ["sh", "-c", "service ssh start; bash"]

#CMD ["sh", "-c", "/usr/sbin/sshd -D ; bash"]

CMD ["/usr/sbin/init"]

二、通过镜像启动后的运行程序修改配置

step1. 编写镜像启动时的运行程序docker-entrypoint.sh

在程序中，为要修改的配置项配置环境变量，并修改配置文件，将配置项的值配置为设置的环境变量

step2. 在DockerFile中指定镜像启动时的entrypoint为docker-entrypoint.sh

例：storm官方Docker镜像中对于storm.yaml配置 https://github.com/31z4/storm-docker/tree/4e9cdba376be0143ba0f041a1099bb7912b145ef/1.2.2 

docker-entrypoint.sh内容如下

#!/bin/bash

set -e

# Allow the container to be started with `--user`if [ "$1" = 'storm' -a "$(id -u)" = '0' ]; then

    chown -R "$STORM_USER" "$STORM_CONF_DIR" "$STORM_DATA_DIR" "$STORM_LOG_DIR"

    exec su-exec "$STORM_USER" "$0" "$@"fi# Generate the config only if it doesn't existCONFIG="$STORM_CONF_DIR/storm.yaml"if [ ! -f "$CONFIG" ]; then

    cat << EOF > "$CONFIG"storm.zookeeper.servers: [zookeeper]

nimbus.seeds: [nimbus]

storm.log.dir: "$STORM_LOG_DIR"storm.local.dir: "$STORM_DATA_DIR"EOFfiexec "$@"

Dockerfile内容如下：

FROM openjdk:8-jre-alpine

# Install required packages

RUN apk add --no-cache \

    bash \

    python \    su-exec

ENV STORM_USER=storm \

    STORM_CONF_DIR=/conf \

    STORM_DATA_DIR=/data \

    STORM_LOG_DIR=/logs

# Add a user and make dirs

RUN set -ex; \

    adduser -D "$STORM_USER"; \    mkdir -p "$STORM_CONF_DIR" "$STORM_DATA_DIR" "$STORM_LOG_DIR"; \    chown -R "$STORM_USER:$STORM_USER" "$STORM_CONF_DIR" "$STORM_DATA_DIR" "$STORM_LOG_DIR"``

ARG GPG_KEY=ACEFE18DD2322E1E84587A148DE03962E80B8FFD

ARG DISTRO_NAME=apache-storm-1.2.2# Download Apache Storm, verify its PGP signature, untar and clean up

RUN set -ex; \

    apk add --no-cache --virtual .build-deps \

      gnupg; \    wget -q "http://www.apache.org/dist/storm/$DISTRO_NAME/$DISTRO_NAME.tar.gz"; \    wget -q "http://www.apache.org/dist/storm/$DISTRO_NAME/$DISTRO_NAME.tar.gz.asc"; \

    export GNUPGHOME="$(mktemp -d)"; \

    gpg --keyserver ha.pool.sks-keyservers.net --recv-key "$GPG_KEY" || \

    gpg --keyserver pgp.mit.edu --recv-keys "$GPG_KEY" || \

    gpg --keyserver keyserver.pgp.com --recv-keys "$GPG_KEY"; \

    gpg --batch --verify "$DISTRO_NAME.tar.gz.asc" "$DISTRO_NAME.tar.gz"; \    tar -xzf "$DISTRO_NAME.tar.gz"; \    chown -R "$STORM_USER:$STORM_USER" "$DISTRO_NAME"; \    rm -rf "$GNUPGHOME" "$DISTRO_NAME.tar.gz" "$DISTRO_NAME.tar.gz.asc"; \

    apk del .build-deps

WORKDIR $DISTRO_NAME

ENV PATH $PATH:/$DISTRO_NAME/bin

COPY docker-entrypoint.sh /ENTRYPOINT ["/docker-entrypoint.sh"]