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221 lines
3.7 KiB
Go
221 lines
3.7 KiB
Go
## 7.10 WORKDIR 指定工作目录
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本节涵盖了相关内容与详细描述，主要探讨以下几个方面：
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### 7.10.1 基本语法
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如下代码块所示，展示了相关示例：
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```docker
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WORKDIR <工作目录路径>
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```
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`WORKDIR` 指定后续指令的工作目录。如果目录不存在，Docker 会自动创建。
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---
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### 7.10.2 基本用法
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如下代码块所示，展示了相关示例：
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```docker
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WORKDIR /app
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RUN pwd # 输出 /app
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RUN echo "hello" > world.txt # 创建 /app/world.txt
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COPY . . # 复制到 /app/
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```
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---
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### 7.10.3 为什么需要 WORKDIR
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本节涵盖了相关内容与详细描述，主要探讨以下几个方面：
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#### 常见错误
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如下代码块所示，展示了相关示例：
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```docker
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## ❌ 错误：cd 在下一个 RUN 中无效
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RUN cd /app
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RUN echo "hello" > world.txt # 文件在根目录！
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```
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#### 原因分析
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如下代码块所示，展示了相关示例：
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```dockerfile
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RUN cd /app
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↓
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启动容器 → cd /app（仅内存变化）→ 提交镜像层 → 容器销毁
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│
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↓ 工作目录未改变！
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RUN echo "hello" > world.txt
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↓
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启动新容器（工作目录在 /）→ 创建 /world.txt
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```
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每个 RUN 都在新容器中执行，**前一个 RUN 的内存状态 (包括工作目录) 不会保留**。
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#### 正确做法
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如下代码块所示，展示了相关示例：
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```docker
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## ✅ 正确：使用 WORKDIR
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WORKDIR /app
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RUN echo "hello" > world.txt # 创建 /app/world.txt
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```
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---
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### 7.10.4 相对路径
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WORKDIR 支持相对路径，基于上一个 WORKDIR：
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```docker
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WORKDIR /a
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WORKDIR b
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WORKDIR c
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RUN pwd # 输出 /a/b/c
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```
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---
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### 7.10.5 使用环境变量
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如下代码块所示，展示了相关示例：
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```docker
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ENV APP_HOME=/app
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WORKDIR $APP_HOME
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RUN pwd # 输出 /app
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```
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---
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### 7.10.6 多阶段构建中的 WORKDIR
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如下代码块所示，展示了相关示例：
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```docker
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## 构建阶段
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FROM node:20 AS builder
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WORKDIR /build
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COPY package*.json ./
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RUN npm install
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COPY . .
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RUN npm run build
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## 生产阶段
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FROM nginx:alpine
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WORKDIR /usr/share/nginx/html
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COPY --from=builder /build/dist .
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```
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---
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### 7.10.7 最佳实践
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本节涵盖了相关内容与详细描述，主要探讨以下几个方面：
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#### 1。尽早设置 WORKDIR
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如下代码块所示，展示了相关示例：
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```docker
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FROM node:20
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WORKDIR /app # 尽早设置
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COPY package*.json ./
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RUN npm install
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COPY . .
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CMD ["node", "server.js"]
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```
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#### 2。使用绝对路径
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如下代码块所示，展示了相关示例：
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```docker
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## ✅ 推荐：绝对路径，意图明确
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WORKDIR /app
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## ⚠️ 避免：相对路径可能造成混淆
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WORKDIR app
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```
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#### 3。不要用 RUN cd
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如下代码块所示，展示了相关示例：
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```docker
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## ❌ 避免
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RUN cd /app && echo "hello" > world.txt
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## ✅ 推荐
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WORKDIR /app
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RUN echo "hello" > world.txt
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```
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#### 4。适时重置 WORKDIR
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如下代码块所示，展示了相关示例：
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```docker
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WORKDIR /app
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## ... 应用相关操作 ...
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WORKDIR /data
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## ... 数据相关操作 ...
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...
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```
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---
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### 7.10.8 与其他指令的关系
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相关信息如下表：
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| 指令 | WORKDIR 的影响 |
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|------|---------------|
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| `RUN` | 在 WORKDIR 中执行命令 |
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| `CMD` | 在 WORKDIR 中启动 |
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| `ENTRYPOINT` | 在 WORKDIR 中启动 |
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| `COPY` | 相对目标路径基于 WORKDIR |
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| `ADD` | 相对目标路径基于 WORKDIR |
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```docker
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WORKDIR /app
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RUN pwd # /app
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COPY . . # 复制到 /app
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CMD ["./start.sh"] # /app/start.sh
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```
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---
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### 7.10.9 运行时覆盖
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使用 `-w` 参数覆盖工作目录：
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```bash
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$ docker run -w /tmp myimage pwd
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/tmp
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```
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---
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