dockerfile保留字

[toc]

参数讲解

from：基础镜像，一般来自哪个（继承）
maintainer：镜像维护者的姓名和邮箱地址
run：容器构建时候执行的命令（docker build)
- shell 格式
- exec 格式
expose：当前容器对外暴露的端口
workdir：指定创建容器后，终端 默认登陆进来的工作目录
user：指定镜像以什么样的用户进行（一般不用，默认是 root）

env：用来在构建镜像过程中设置环境变量

ENV CATALINA_HOME /usr/local/tomcat
ENV PATH $CATALINA_HOME/bin:$PATH
RUN mkdir -p "$CATALINA_HOME"
WORKDIR $CATALINA_HOME

add：将宿主目录下的文件拷贝到镜像且自动处理URL和解压的tar压缩包(一般使用copy不使用add)
copy：（类似于add），将构建的文件、目录复制到新的一层镜像内
· COPY src dest
· COPY ["src", "dest"]
· <src源路径>：源文件或者源目录
· <dest目标路径>：容器内的指定路径，该路径不用事先建好，路径不存在的话，会自动创建。
volume：容器卷，相当于-v
cmd：启动容器后需要做的事情
- 类似于run，也支持 shell 或者 exec
- dockerfile 中可以用多个cmd指令，但 只有最后一个生效，cmd 会被 docker run 之后的参数替换
- 可以想到是bin/bash，catalina.sh 将其覆盖
```
EXPOSE 8080
CMD ["catalina.sh", "run"]
```
entrypoint：也是用来指定一个容器启动时要运行的命令，看后面警告信息~
- 类似于cmd指令，可以和cmd一起用

CMD 和 RUN 区别

CMD 是 docker run 时运行 ⚠️
RUN 是 docker build 时运行 ⚠️

ENTRYPOINT 区别 CMD 会被 Dockerfile 后面参数覆盖，ENTRYPOINT 不会，而且这些参数会被当作参数送给 ENTRYPOINT 指令指定的程序

⚡组合使用，我们构建 nginx:test镜像：

FORM nginx

ENTRYPOINT ["nginx", "-c"]  # 定参
CMD ["/etc/nginx/nginx.conf"]  #变参

时否传参	按照dockerfile编写执行	传参运行
`docker` 命令	`docke run nginx:test`	`docker run nginx:test -c /etc/nginx/new.conf`
衍生出的实际命令	`nginx -c /etc/nginx/nginx.conf`	`nginx -c /etc/nginx/new.conf`

一些自己的📜 对上面的解释

我们在使用 RUN 的时候可以想象为：

RUN ["./test.php" , "dev", "offline"] 等价于 RUN ./test.php dev offline

为什么需要设置环境变量？

ENV MY_PATH /usr/mytest

环境变量也是可以和 RUN 一起用的，或者是工作目录：

RUN makir -p "MY_PATH"
WORKDIR /MY_PATH

就是方便使用而已~

关于 ADD 和 COPY 我比较倾向于 ADD ，它更强大。能处理 URL 类似于 wget，自动帮你下载远程文件。

Dockerfile 可以有多个 CMD 指令，但是只有最后一个生效，CMD 会被 docker run 之后的参数替换，如：

docker run -it -p 8080:8080 tomcat /bin/bash

/bin/bash 最后替换了原有 CMD ，此时会出现找不到服务器~

上手

我们以创建一个dockerfile为例

创建Dockerfile文件，注意一定要是D大写

touch Dockerfile

编写Dockerfile：

💡 注意：除了FROM语句其他都是非必须的！

FROM aloine
# 指定shell语句运行在哪个路径下
WORKDIR /app  
# 将宿主机的文件拷贝到容器app下面
COPY src/ /app
#运行的是shell语句
RUN echo 321 >> 1.txt
#一般执行CMD后就结束了，所以选择的是阻塞式脚本 
CMD tail -f 1.txt

运行Dockerfile脚本

-t 指定名称
. 指定当前目录下

docker build -t test .

运行：

docker run test

参考dockerfile

参考tomcat8的dockerfile入门

不管我们远程拉取的热门容器，或者是自己打包的镜像，都需要 dockerfile 作为支撑。

https://github.com/docker-library/tomcat/blob/master/10.0/jdk8/corretto/Dockerfile

# NOTE: THIS DOCKERFILE IS GENERATED VIA "apply-templates.sh"
#
# PLEASE DO NOT EDIT IT DIRECTLY.
#

FROM amazoncorretto:8
# 基础镜像，一般来自哪个

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

# see https://www.apache.org/dist/tomcat/tomcat-10/KEYS
# see also "versions.sh" (https://github.com/docker-library/tomcat/blob/master/versions.sh)
ENV GPG_KEYS A9C5DF4D22E99998D9875A5110C01C5A2F6059E7

ENV TOMCAT_MAJOR 10
ENV TOMCAT_VERSION 10.0.20
ENV TOMCAT_SHA512 53bfdbac2e6af5cca97dc01fffb0428380fbe21d8375f45d015c16a57017ff946fdc555ebad9e9fcbcb97b438c4f6daf3aa39d36ca79fd5a372cfc1a80b7117f

RUN set -eux; \
	\
# http://yum.baseurl.org/wiki/YumDB.html
	if ! command -v yumdb > /dev/null; then \
		yum install -y 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 $todo; \
			yumdb set reason dep $todo; \
		fi; \
	) }; \
	_yum_install_temporary gzip tar; \
	\
	ddist() { \
		local f="$1"; shift; \
		local distFile="$1"; shift; \
		local mvnFile="${1:-}"; \
		local success=; \
		local distUrl=; \
		for distUrl in \
# https://issues.apache.org/jira/browse/INFRA-8753?focusedCommentId=14735394#comment-14735394
			"https://www.apache.org/dyn/closer.cgi?action=download&filename=$distFile" \
# if the version is outdated (or we're grabbing the .asc file), we might have to pull from the dist/archive :/
			"https://downloads.apache.org/$distFile" \
			"https://www-us.apache.org/dist/$distFile" \
			"https://www.apache.org/dist/$distFile" \
			"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-$TOMCAT_VERSION.tar.gz.asc"; \
	export GNUPGHOME="$(mktemp -d)"; \
	for key in $GPG_KEYS; do \
		gpg --batch --keyserver keyserver.ubuntu.com --recv-keys "$key"; \
	done; \
	gpg --batch --verify tomcat.tar.gz.asc tomcat.tar.gz; \
	tar -xf tomcat.tar.gz --strip-components=1; \
	rm bin/*.bat; \
	rm tomcat.tar.gz*; \
	command -v gpgconf && gpgconf --kill all || :; \
	rm -rf "$GNUPGHOME"; \
	\
# https://tomcat.apache.org/tomcat-9.0-doc/security-howto.html#Default_web_applications
	mv webapps webapps.dist; \
	mkdir webapps; \
# we don't delete them completely because they're frankly a pain to get back for users who do want them, and they're generally tiny (~7MB)
	\
	nativeBuildDir="$(mktemp -d)"; \
	tar -xf bin/tomcat-native.tar.gz -C "$nativeBuildDir" --strip-components=1; \
	_yum_install_temporary \
		apr-devel \
		gcc \
		make \
		openssl11-devel \
	; \
	( \
		export CATALINA_HOME="$PWD"; \
		cd "$nativeBuildDir/native"; \
		aprConfig="$(command -v apr-1-config)"; \
		./configure \
			--libdir="$TOMCAT_NATIVE_LIBDIR" \
			--prefix="$CATALINA_HOME" \
			--with-apr="$aprConfig" \
			--with-java-home="$JAVA_HOME" \
			--with-ssl=yes \
		; \
		nproc="$(nproc)"; \
		make -j "$nproc"; \
		make install; \
	); \
	rm -rf "$nativeBuildDir"; \
	rm bin/tomcat-native.tar.gz; \
	\
# mark any explicit dependencies as manually installed
	find "$TOMCAT_NATIVE_LIBDIR" -type f -executable -exec ldd '{}' ';' \
		| awk '/=>/ && $(NF-1) != "=>" { print $(NF-1) }' \
		| xargs -rt readlink -e \
		| sort -u \
		| xargs -rt rpm --query --whatprovides \
		| sort -u \
		| tee "$TOMCAT_NATIVE_LIBDIR/.dependencies.txt" \
		| xargs -r yumdb set reason user \
	; \
	\
# clean up anything added temporarily and not later marked as necessary
	yum autoremove -y; \
	yum clean all; \
	rm -rf /var/cache/yum; \
	\
# sh removes env vars it doesn't support (ones with periods)
# https://github.com/docker-library/tomcat/issues/77
	find ./bin/ -name '*.sh' -exec sed -ri 's|^#!/bin/sh$|#!/usr/bin/env bash|' '{}' +; \
	\
# fix permissions (especially for running as non-root)
# https://github.com/docker-library/tomcat/issues/35
	chmod -R +rX .; \
	chmod 777 logs temp work; \
	\
# smoke test
	catalina.sh version

# verify Tomcat Native is working properly
RUN set -eux; \
	nativeLines="$(catalina.sh configtest 2>&1)"; \
	nativeLines="$(echo "$nativeLines" | grep 'Apache Tomcat Native')"; \
	nativeLines="$(echo "$nativeLines" | sort -u)"; \
	if ! echo "$nativeLines" | grep -E 'INFO: Loaded( APR based)? Apache Tomcat Native library' >&2; then \
		echo >&2 "$nativeLines"; \
		exit 1; \
	fi

EXPOSE 8080
CMD ["catalina.sh", "run"]

补充：

案例如下：假设已通过 Dockerfile 构建了 nginx:test 镜像：

是否传参	按照dockerfile编写执行	传参运行
Docker命令	docker run nginx:test	docker run nginx:test -c /etc/nginx/new.conf
衍生出的实际命令	nginx -c /etc/nginx/nginx.conf	nginx -c /etc/nginx/new.conf

ENV MY_PATH /usr/mytest

这个环境变量可以在后续的任何RUN指令中使用，这就如同在命令前面指定了环境变量前缀一样；

也可以在其它指令中直接使用这些环境变量，

比如：WORKDIR $MY_PATH

# dockerfile保留字

# 参数讲解

# 上手

# 参考dockerfile

# 补充：

dockerfile保留字

参数讲解

上手

参考dockerfile

补充：