Docker已启动容器安装Pillow失效，Django项目报错求助

问题背景 #

用Docker构建Django应用，容器已创建完成后给模型添加了ImageField，执行docker-compose run web python3 manage.py makemigrations时触发报错，提示需安装Pillow：

web_1  | Watching for file changes with StatReloader
web_1  | Performing system checks...
web_1  | 
web_1  | Exception in thread django-main-thread:
web_1  | Traceback (most recent call last):
web_1  |   File "/usr/local/lib/python3.12/threading.py", line 1052, in _bootstrap_inner
web_1  |     self.run()
web_1  |   File "/usr/local/lib/python3.12/threading.py", line 989, in run
web_1  |     self._target(*self._args, **self._kwargs)
web_1  |   File "/usr/local/lib/python3.12/site-packages/django/utils/autoreload.py", line 64, in wrapper
web_1  |     fn(*args, **kwargs)
web_1  |   File "/usr/local/lib/python3.12/site-packages/django/core/management/commands/runserver.py", line 133, in inner_run
web_1  |     self.check(display_num_errors=True)
web_1  |   File "/usr/local/lib/python3.12/site-packages/django/core/management/base.py", line 556, in check
web_1  |     raise SystemCheckError(msg)
web_1  | django.core.management.base.SystemCheckError: SystemCheckError: System check identified some issues:
web_1  | 
web_1  | ERRORS:
web_1  | system.Task.image: (fields.E210) Cannot use ImageField because Pillow is not installed.
web_1  |    HINT: Get Pillow at https://pypi.org/project/Pillow/ or run command "python -m pip install Pillow".

已尝试的无效操作 #

• 执行docker-compose run web python3 -m pip install Pillow，安装日志显示成功，但重启容器后报错依旧：

Starting db ... done
Creating app_web_run ... done
Collecting Pillow
  Obtaining dependency information for Pillow from https://files.pythonhosted.org/packages/44/ed/a6f7dcd6631ec55b8d26c6a8bca762b04b7025daa3aa67e860a886abed89/Pillow-10.1.0-cp312-cp312-manylinux_2_28_x86_64.whl.metadata
  Downloading Pillow-10.1.0-cp312-cp312-manylinux_2_28_x86_64.whl.metadata (9.5 kB)
Downloading Pillow-10.1.0-cp312-cp312-manylinux_2_28_x86_64.whl (3.6 MB)
   ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 3.6/3.6 MB 287.0 kB/s eta 0:00:00
Installing collected packages: Pillow
Successfully installed Pillow-10.1.0
WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv

• 通过docker exec -it <容器ID/名称> bash进入容器安装Pillow，pip list显示已安装，但容器重启后问题重复出现。
• 尝试通过Dockerfile重新构建镜像，但未解决问题。

当前使用的配置文件 #

Dockerfile #

FROM python:3

ENV PYTHONUNBUFFERED=1

WORKDIR /code
COPY requirements.txt /code/

RUN pip install --upgrade pip
RUN apk --update add \
    build-base \
    jpeg-dev \
    zlib-dev
RUN pip install --no-cache-dir -r requirements.txt
COPY . /code/

docker-compose.yml #

version: "3.11"

services:
  db:
    container_name: db
    image: postgres
    volumes:
      - ./data/db:/var/lib/postgresql/data
    environment:
      - POSTGRES_DB=postgres
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=postgres

  web:
    build:
      context: .
      dockerfile: Dockerfile
    command: python3 manage.py runserver 0.0.0.0:8000
    volumes:
      - .:/code
    ports:
      - "8000:8000"

    depends_on:
      - db

解决方案 #

问题根源 #

1. 直接在容器内安装Pillow是临时操作，容器重启后所有修改会丢失——容器基于镜像运行，镜像未更新的话，每次重启都是全新实例。
2. Dockerfile构建无效的原因是未将Pillow添加到requirements.txt，导致构建镜像时不会自动安装该依赖。
3. Dockerfile中使用了apk命令（Alpine系统包管理器），但基础镜像python:3基于Debian，Debian使用apt-get而非apk，这会导致依赖安装失败。

修复步骤 #

1. 在本地项目的requirements.txt中添加一行：Pillow（或指定版本如Pillow==10.1.0）
2. 修改Dockerfile中的依赖安装命令，适配Debian系统：

FROM python:3

ENV PYTHONUNBUFFERED=1

WORKDIR /code
COPY requirements.txt /code/

RUN pip install --upgrade pip
# 替换apk为apt-get，安装Pillow编译依赖
RUN apt-get update && apt-get install -y --no-install-recommends \
    build-essential \
    libjpeg-dev \
    zlib1g-dev \
    && rm -rf /var/lib/apt/lists/*
RUN pip install --no-cache-dir -r requirements.txt
COPY . /code/

3. 重新构建镜像：docker-compose build web
4. 重启容器：docker-compose up

内容的提问来源于stack exchange，提问作者General Suslik