如果我删除几行代码，Docker 映像大小会增加

Question

我正在尝试减小docker映像的大小，但是Dockerfile很奇怪。

我连接RUN命令以减小图像的大小。当我构建下面的 Dockerfile 时，它只创建 235MB。

FROM nginx:alpine
RUN apk add --no-cache --virtual .build-deps 
        gcc 
        libc-dev 
        make 
        openssl 
        pcre-dev 
        zlib-dev 
        linux-headers 
        curl 
        gnupg 
        libxslt-dev 
        gd-dev 
        perl-dev 
    && apk add --no-cache --virtual .libmodsecurity-deps 
        pcre-dev 
        libxml2-dev 
        git 
        libtool 
        automake 
        autoconf 
        g++ 
        flex 
        bison 
        yajl-dev 
        git 
    # Add runtime dependencies that should not be removed
    && apk add --no-cache 
        doxygen 
        geoip 
        geoip-dev 
        yajl 
        libstdc++ 
        sed 
    # Installing ModSec Library version 3
    && echo "Installing ModSec Library" 
    && git clone -b v3/master --single-branch https://github.com/SpiderLabs/ModSecurity /opt/ModSecurity 
    && cd /opt/ModSecurity 
    && git submodule init 
    && git submodule update 
    && ./build.sh 
    && ./configure && make && make install 
    && echo "Finished Installing ModSec Library" 
    # Installing ModSec - Nginx connector
    && cd /opt 
    && echo 'Installing ModSec - Nginx connector' 
    && git clone --depth 1 https://github.com/SpiderLabs/ModSecurity-nginx.git 
    && wget http://nginx.org/download/nginx-$NGINX_VERSION.tar.gz 
    && tar zxvf nginx-$NGINX_VERSION.tar.gz 
    # Adding Nginx Connector Module
    && cd /opt/nginx-$NGINX_VERSION  
    && ./configure --with-compat --add-dynamic-module=../ModSecurity-nginx 
    && make modules 
    && cp objs/ngx_http_modsecurity_module.so /etc/nginx/modules 
    && echo "Finished Installing ModSec - Nginx connector" 
    # Begin installing ModSec OWASP Rules
    && echo "Begin installing ModSec OWASP Rules" 
    && mkdir /etc/nginx/modsec 
    && wget -P /etc/nginx/modsec/ https://raw.githubusercontent.com/SpiderLabs/ModSecurity/v3/master/modsecurity.conf-recommended 
    && mv /etc/nginx/modsec/modsecurity.conf-recommended /etc/nginx/modsec/modsecurity.conf 
    && sed -i 's/SecRuleEngine DetectionOnly/SecRuleEngine On/' /etc/nginx/modsec/modsecurity.conf 
    # Fetching owasp-modsecurity-crs
    && cd /opt 
    && git clone -b v3.0/master https://github.com/SpiderLabs/owasp-modsecurity-crs 
    && mv owasp-modsecurity-crs/ /usr/local/ 
    && cp /usr/local/owasp-modsecurity-crs/crs-setup.conf.example /usr/local/owasp-modsecurity-crs/crs-setup.conf 
    # Creating modsec file
    && echo 'Creating modsec file' 
    && echo -e '# From https://github.com/SpiderLabs/ModSecurity/blob/master/n 
      # modsecurity.conf-recommendedn 
      # Edit to set SecRuleEngine Onn 
      Include "/etc/nginx/modsec/modsecurity.conf"n 
      # OWASP CRS v3 rulesn 
      Include "/usr/local/owasp-modsecurity-crs/crs-setup.conf"n 
      Include "/usr/local/owasp-modsecurity-crs/rules/*.conf"'
      >>/etc/nginx/modsec/main.conf 
    && chown nginx:nginx /etc/nginx/modsec/main.conf 
    # Removing old Nginx conf files
    && rm -fr /etc/nginx/conf.d/ 
    && rm -fr /etc/nginx/nginx.conf 
    && chown -R nginx:nginx /usr/share/nginx 
    # delete uneeded and clean up
    && apk del .build-deps 
    && apk del .libmodsecurity-deps 
    && rm -fr ModSecurity 
    && rm -fr ModSecurity-nginx 
    && rm -fr nginx-$NGINX_VERSION.tar.gz 
    && rm -fr nginx-$NGINX_VERSION
COPY conf/nginx.conf /etc/nginx
COPY conf/conf.d /etc/nginx/conf.d
COPY errors /usr/share/nginx/errors
WORKDIR /usr/share/nginx/html
CMD nginx -g 'daemon off;'
EXPOSE 80

我已经看过 docker 历史记录 imagedId 它显示此 RUN 命令的大小增加了大约 855MB。有人明白为什么它表现得很奇怪吗？

任何想法都会很有帮助，很难每次都调试构建映像。

Answer 1

我尝试以两种方式构建，发现没有太大区别。
大部分磁盘空间由/opt/ModSecurity
占用。最初在 git 克隆后它是 74MB。

$ docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
oldimage            latest              924a8d4f941e        11 minutes ago      867MB
newimage            latest              d1ca029927c2        About an hour ago   867MB
nginx               alpine              ebe2c7c61055        6 days ago          18MB

但是，在构建完整构建后 - 它已增长到 ~650MB。

$ du -sh *
639.7M  ModSecurity
408.0K  ModSecurity-nginx
7.5M    nginx-1.13.12
996.0K  nginx-1.13.12.tar.gz