Dockerfile 跨阶段多阶段使用 ARG 命令

若要想 Dockerfile 的 ARG 命令可以跨多个阶段使用，需要有以下几步：

1. 先在文件最前面使用 ARG 命令定义
2. 然后在每个阶段分别引用 ARG 命令使用

一个示范的 Dockerfile 文件如下：

# global argument, can cross multiple stages
ARG APP_HOME=/home/web/app

# build stage
FROM node:16-alpine as builder
ARG APP_HOME
# maintainer info
LABEL maintainer="FengYin Xu"
# Create app directory
WORKDIR ${APP_HOME}/
# Install app dependencies
# A wildcard is used to ensure both package.json AND package-lock.json are copied
# where available (npm@5+)
COPY package*.json ${APP_HOME}/
RUN npm install
# build production package
COPY . ${APP_HOME}/
RUN npm run build

# deploy stage
FROM nginx:alpine
ARG APP_HOME
COPY --from=builder ${APP_HOME}/build /usr/share/nginx/html
COPY --from=builder ${APP_HOME}/nginx.conf /etc/nginx/conf.d
EXPOSE 80
CMD ["nginx", "-g", "daemon off;"]

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