核心原则： 不要手动进入容器改文件，而是重新构建镜像 → 删除旧容器 → 运行新容器。

第 16 步操作

1. 修改 app.py，改变返回内容

cd ~/my-python-app cat > app.py << 'EOF' from http.server import HTTPServer, BaseHTTPRequestHandler
import datetime

class Handler(BaseHTTPRequestHandler):
    def do_GET(self):
        self.send_response(200)
        self.send_header('Content-type', 'text/html')
        self.end_headers()
        now = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
        message = f'<h1>Updated! Current time: {now}</h1>'
        self.wfile.write(message.encode())

if __name__ == '__main__':
    print('Starting server on port 8000...')
    HTTPServer(('0.0.0.0', 8000), Handler).serve_forever()
EOF

2. 重新构建 alpine 镜像（用同样的 tag，会覆盖旧镜像）

docker build -t my-python-app:alpine -f Dockerfile.optimized .

注意：由于 COPY app.py 这一层缓存失效，Docker 会重新执行这一层和之后的层。

3. 停止并删除旧容器

docker stop my-app-alpine docker rm my-app-alpine

4. 运行新容器

docker run -d --name my-app-alpine -p 8001:8000 my-python-app:alpine

5. 测试更新后的内容

curl http://localhost:8001

root@docker-test:~/my-python-app# cd ~/my-python-app
root@docker-test:~/my-python-app# cat > app.py << 'EOF'
> from http.server import HTTPServer, BaseHTTPRequestHandler
> import datetime
> 
> class Handler(BaseHTTPRequestHandler):
>     def do_GET(self):
>         self.send_response(200)
>         self.send_header('Content-type', 'text/html')
>         self.end_headers()
>         now = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
>         message = f'<h1>Updated! Current time: {now}</h1>'
>         self.wfile.write(message.encode())
> 
> if __name__ == '__main__':
>     print('Starting server on port 8000...')
>     HTTPServer(('0.0.0.0', 8000), Handler).serve_forever()
> EOF
root@docker-test:~/my-python-app# ll
total 20
drwxr-xr-x  2 root root 4096 May 12 08:27 ./
drwx------ 11 root root 4096 May 12 08:27 ../
-rw-r--r--  1 root root  552 May 12 08:33 app.py
-rw-r--r--  1 root root  223 May 12 08:21 Dockerfile
-rw-r--r--  1 root root  201 May 12 08:27 Dockerfile.optimized
root@docker-test:~/my-python-app# docker build -t my-python-app:alpine -f Dockerfile.optimized .
[+] Building 0.2s (8/8) FINISHED                                                        docker:default
 => [internal] load build definition from Dockerfile.optimized                                    0.0s
 => => transferring dockerfile: 250B                                                              0.0s
 => [internal] load metadata for docker.io/library/python:3.9-alpine                              0.1s
 => [internal] load .dockerignore                                                                 0.0s
 => => transferring context: 2B                                                                   0.0s
 => [1/3] FROM docker.io/library/python:3.9-alpine@sha256:c99b6eb43b3ac4d750db3d6e8b22268d5ea9a9  0.0s
 => [internal] load build context                                                                 0.0s
 => => transferring context: 587B                                                                 0.0s
 => CACHED [2/3] WORKDIR /app                                                                     0.0s
 => [3/3] COPY app.py .                                                                           0.0s
 => exporting to image                                                                            0.0s
 => => exporting layers                                                                           0.0s
 => => writing image sha256:e7c452100cf157732dbf140e3c472cdb8b896562f59af5d9ca384acf04140651      0.0s
 => => naming to docker.io/library/my-python-app:alpine                                           0.0s
root@docker-test:~/my-python-app# docker stop my-app-alpine 
my-app-alpine
root@docker-test:~/my-python-app# docker rm my-app-alpine 
my-app-alpine
root@docker-test:~/my-python-app# docker run -d --name my-app-alpine -p 8001:8000 my-python-app:alpine f7905eb9dd30bf250a9c827d0fe40d3a515ccbc19b33468bf95aa8060d26bff9
root@docker-test:~/my-python-app# curl http://localhost:8001
<h1>Updated! Current time: 2026-05-12 08:35:03</h1>root@docker-test:~/my-python-app#