10 . Docker 中的 DockerFile 解析(各种指令阐明)
Docker file 是用来构建 Docker 镜像的文本文件，是由一条条构建镜像所需的指令和参数构成的脚本。
官方地址：https://docs.docker.com/engine/reference/builder/
1. DockerFile 构建过程解析
Docker file 内容基础知识
- 每条保留字指令都必须为大写字母 且背面要跟随至少一个参数。
- 指令按照从上到下，顺序执行。
- # 表现表明
- 每条指令都会创建一个新的镜像层并对镜像举行提交。
Docker执行 Dockerfile的大抵流程
- docker 从基础镜像运行一个容器
- 执行一条指令并对容器作出修改
- 执行雷同 docker commit 的利用提交一个新的镜像层。
- docker 再基于刚提交的镜像运行一个新容器
- 执行 dockerfile 中的下一条指令直到全部指令都执行完成。
从应用软件的角度来看，Dockerfile、Docker镜像与Docker容器分别代表软件的三个差别阶段，
- Dockerfile是软件的原材料
- Docker镜像是软件的交付品
- Docker容器则可以认为是软件镜像的运行态，也即依照镜像运行的容器实例
Dockerfile面向开辟，Docker镜像成为交付尺度，Docker容器则涉及摆设与运维，三者缺一不可，协力充当Docker体系的基石。
- Dockerfile，需要定义一个Dockerfile，Dockerfile定义了进程需要的一切东西。Dockerfile涉及的内容包括执行代码大概是文件、情况变量、依靠包、运行时情况、动态链接库、利用系统的发行版、服务进程和内核进程(当应用进程需要和系统服务和内核进程打交道，这时需要思量如何设计namespace的权限控制)等等;
- Docker镜像，在用 Dockerfile 定义一个文件之后，docker build 时会产生一个Docker镜像，当运行 Docker镜像时会真正开始提供服务;
2. DockerFile 常用保留字指令
参考 tomcat8 的dockerfile入门：https://github.com/docker-library/tomcat/blob/master/Dockerfile.template
[code]{{
include "from"
;
include "shared"
-}}
FROM {{ from }}
ENV CATALINA_HOME /usr/local/tomcat
ENV PATH $CATALINA_HOME/bin PATH
RUN mkdir -p "$CATALINA_HOME"
WORKDIR $CATALINA_HOME
# let "Tomcat Native" live somewhere isolated
ENV TOMCAT_NATIVE_LIBDIR $CATALINA_HOME/native-jni-lib
ENV LD_LIBRARY_PATH ${LD_LIBRARY_PATH:+$LD_LIBRARY_PATH:}$TOMCAT_NATIVE_LIBDIR
ENV TOMCAT_MAJOR {{ major }}
ENV TOMCAT_VERSION {{ .version }}
ENV TOMCAT_SHA512 {{ .sha512 }}
{{ if java_variant == "jdk" then ( -}}
RUN set -eux; \
\
{{ if is_apt then ( -}}
savedAptMark="$(apt-mark showmanual)"; \
apt-get update; \
apt-get install -y --no-install-recommends \
ca-certificates \
curl \
gnupg \
; \
{{ ) else ( -}}
# http://yum.baseurl.org/wiki/YumDB.html
if ! command -v yumdb > /dev/null; then \
yum install -y --setopt=skip_missing_names_on_install=False yum-utils; \
yumdb set reason dep yum-utils; \
fi; \
# a helper function to "yum install" things, but only if they aren't installed (and to set their "reason" to "dep" so "yum autoremove" can purge them for us)
_yum_install_temporary() { ( set -eu +x; \
local pkg todo=''; \
for pkg; do \
if ! rpm --query "$pkg" > /dev/null 2>&1; then \
todo="$todo $pkg"; \
fi; \
done; \
if [ -n "$todo" ]; then \
set -x; \
yum install -y --setopt=skip_missing_names_on_install=False $todo; \
yumdb set reason dep $todo; \
fi; \
) }; \
_yum_install_temporary gzip tar; \
{{ ) end -}}
\
ddist() { \
local f="$1"; shift; \
local distFile="$1"; shift; \
local mvnFile="${1:-}"; \
local success=; \
local distUrl=; \
for distUrl in \
# https://apache.org/history/mirror-history.html
"https://dlcdn.apache.org/$distFile" \
# if the version is outdated, we have to pull from the archive
"https://archive.apache.org/dist/$distFile" \
# if all else fails, let's try Maven (https://www.mail-archive.com/users@tomcat.apache.org/msg134940.html; https://mvnrepository.com/artifact/org.apache.tomcat/tomcat; https://repo1.maven.org/maven2/org/apache/tomcat/tomcat/)
${mvnFile:+"https://repo1.maven.org/maven2/org/apache/tomcat/tomcat/$mvnFile"} \
; do \
if curl -fL -o "$f" "$distUrl" && [ -s "$f" ]; then \
success=1; \
break; \
fi; \
done; \
[ -n "$success" ]; \
}; \
\
ddist 'tomcat.tar.gz' "tomcat/tomcat-$TOMCAT_MAJOR/v$TOMCAT_VERSION/bin/apache-tomcat-$TOMCAT_VERSION.tar.gz" "$TOMCAT_VERSION/tomcat-$TOMCAT_VERSION.tar.gz"; \
echo "$TOMCAT_SHA512 *tomcat.tar.gz" | sha512sum --strict --check -; \
ddist 'tomcat.tar.gz.asc' "tomcat/tomcat-$TOMCAT_MAJOR/v$TOMCAT_VERSION/bin/apache-tomcat-$TOMCAT_VERSION.tar.gz.asc" "$TOMCAT_VERSION/tomcat-$TOMCAT_VERSION.tar.gz.asc"; \
GNUPGHOME="$(mktemp -d)"; export GNUPGHOME; \
curl -fL -o upstream-KEYS {{ "https://www.apache.org/dist/tomcat/tomcat-\(major)/KEYS" | @sh }}; \
gpg --batch --import upstream-KEYS; \
# filter upstream KEYS file to *just* known/precomputed fingerprints
printf '' > filtered-KEYS; \
# see https://www.apache.org/dist/tomcat/tomcat-{{ major }}/KEYS
for key in \
{{
# docker run --rm buildpack-deps:bookworm-curl bash -c 'wget -qO- https://www.apache.org/dist/tomcat/tomcat-11/KEYS | gpg --batch --import &> /dev/null && gpg --batch --list-keys --with-fingerprint --with-colons' | awk -F: '$1 == "pub" && $2 == "-" { pub = 1 } pub && $1 == "fpr" { fpr = $10 } $1 == "sub" { pub = 0 } pub && fpr && $1 == "uid" && $2 == "-" { print "\t\t\t#", $10; print "\t\t\t\"" fpr "\","; pub = 0 } END { print "\t\t\t# trailing comma |
