基于Ubuntu的Docker镜像中Python可执行文件缺失问题求助

基于Ubuntu基础镜像用docker-compose构建4个镜像时，celery_worker、celery_beat和flower这3个容器的entrypoint脚本执行失败，提示找不到python可执行文件。进入容器后发现二进制文件实际为python3.10，在Dockerfile里创建了符号链接ln -s /usr/bin/python3.10 /usr/bin/python，但该链接在这三个容器里不生效，web容器则正常。

测试结果 #

Web容器测试 #

$ docker-compose exec web bash
root@9feff05c4ea1:/app# python
Python 3.10.4 (main, Jun 29 2022, 12:14:53) [GCC 11.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

Flower容器测试 #

$ docker-compose exec flower bash
root@fa9d93403410:/app# python
bash: python: command not found

相关配置文件 #

docker-compose.yml #

version: '3.8'

services:
  web:
    build:
      context: .
      dockerfile: ./compose/local/django/Dockerfile
    image: front_office
    command: /start
    volumes:
      - .:/app
    ports:
      - 8010:8000
    env_file:
      - ./front_office/.env
    depends_on:
      - redis
      - db

  db:
    image: postgres
    volumes:
      - postgres_data:/var/lib/postgresql/data/
    environment:
      - POSTGRES_DB=hello_django
      - POSTGRES_USER=hello_django
      - POSTGRES_PASSWORD=hello_django

  redis:
    image: redis

  celery_worker:
    build:
      context: .
      dockerfile: ./compose/local/django/Dockerfile
    image: front_office_worker
    command: /start-celeryworker
    volumes:
      - .:/app
    env_file:
      - ./front_office/.env
    depends_on:
      - redis
      - db

  celery_beat:
    build:
      context: .
      dockerfile: ./compose/local/django/Dockerfile
    image: front_office_beat
    command: /start-celerybeat
    volumes:
      - .:/app
    env_file:
      - ./front_office/.env
    depends_on:
      - redis
      - db

  flower:
    build:
      context: .
      dockerfile: ./compose/local/django/Dockerfile
    image: front_office_flower
    command: /start-flower
    volumes:
      - .:/app
    env_file:
      - ./front_office/.env
    ports:
      - 5557:5555
    depends_on:
      - redis
      - db

volumes:
  postgres_data:

Dockerfile #

FROM ubuntu

ENV PYTHONUNBUFFERED 1
ENV PYTHONDONTWRITEBYTECODE 1

RUN apt-get update \
  && apt-get install -y build-essential \
  && apt-get install -y libpq-dev \
  && apt-get install -y gettext \
  && apt-get install -y python3.10 \
  && apt-get install -y python-pip \
  && apt-get install -y python3-pip \
  && apt-get install -y git \
  && apt-get install -y openssh-client \
  && apt-get install -y libcurl4-openssl-dev libssl-dev \
  && apt-get install -y python3-requests \
  && apt-get install -y cargo \
  && apt-get install -y procps \
  && apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false \
  && rm -rf /var/lib/apt/lists/*

RUN ln -s /usr/bin/python3.10 /usr/bin/python

# Requirements are installed here to ensure they will be cached.
COPY ./requirements.txt /requirements.txt
RUN pip install -r /requirements.txt

COPY ./compose/local/django/entrypoint /entrypoint
RUN sed -i 's/\r$//g' /entrypoint
RUN chmod +x /entrypoint

COPY ./compose/local/django/start /start
RUN sed -i 's/\r$//g' /start
RUN chmod +x /start

COPY ./compose/local/django/celery/worker/start /start-celeryworker
RUN sed -i 's/\r$//g' /start-celeryworker
RUN chmod +x /start-celeryworker

COPY ./compose/local/django/celery/beat/start /start-celerybeat
RUN sed -i 's/\r$//g' /start-celerybeat
RUN chmod +x /start-celerybeat

COPY ./compose/local/django/celery/flower/start /start-flower
RUN sed -i 's/\r$//g' /start-flower
RUN chmod +x /start-flower

WORKDIR /app

ENTRYPOINT ["/entrypoint"]

entrypoint脚本 #

#!/bin/bash

# if any of the commands in your code fails for any reason, the entire script fails
set -o errexit
# fail exit if one of your pipe command fails
set -o pipefail
# exits if any of your variables is not set
set -o nounset

postgres_ready() {
python << END
import sys

import psycopg2

try:
    psycopg2.connect(
        dbname="${SQL_DATABASE}",
        user="${SQL_USER}",
        password="${SQL_PASSWORD}",
        host="${SQL_HOST}",
        port="${SQL_PORT}",
    )
except psycopg2.OperationalError:
    sys.exit(-1)
sys.exit(0)

END
}
until postgres_ready; do
  >&2 echo 'Waiting for PostgreSQL to become available...'
  sleep 1
done
>&2 echo 'PostgreSQL is available'

exec "$@"

容器日志 #

front_office-celery_worker-1  | Waiting for PostgreSQL to become available...
front_office-celery_worker-1  | /entrypoint: line 11: python: command not found
front_office-celery_worker-1  | Waiting for PostgreSQL to become available...
front_office-celery_beat-1    | /entrypoint: line 11: python: command not found
front_office-celery_beat-1    | Waiting for PostgreSQL to become available...
front_office-celery_worker-1  | /entrypoint: line 11: python: command not found
front_office-celery_worker-1  | Waiting for PostgreSQL to become available...
front_office-flower-1         | /entrypoint: line 11: python: command not found
front_office-flower-1         | Waiting for PostgreSQL to become available...
front_office-celery_beat-1    | /entrypoint: line 11: python: command not found
front_office-celery_beat-1    | Waiting for PostgreSQL to become available...
front_office-flower-1         | /entrypoint: line 11: python: command not found
front_office-flower-1         | Waiting for PostgreSQL to become available...
front_office-celery_worker-1  | /entrypoint: line 11: python: command not found

解决方案 #

方法1：强制重新构建镜像，避免缓存问题 #

符号链接命令本身正确，但可能因为镜像缓存导致新修改未生效，执行以下命令强制重新构建所有服务：

docker-compose build --no-cache
docker-compose up -d

方法2：直接修改entrypoint脚本使用python3.10 #

如果符号链接仍不生效，直接在entrypoint脚本中替换python为python3.10：

postgres_ready() {
python3.10 << END
# ... 原有代码保持不变
END
}

方法3：用update-alternatives设置默认Python版本（更规范） #

在Dockerfile中替换手动创建符号链接的命令，使用Ubuntu官方工具设置默认Python：

RUN update-alternatives --install /usr/bin/python python /usr/bin/python3.10 1
RUN update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.10 1

该方式比手动创建符号链接更稳定，能确保系统全局识别python命令。

方法4：检查volume挂载是否干扰系统目录 #

确认docker-compose中所有服务的volume仅挂载本地目录到容器/app，没有误挂载到/usr/bin等系统目录，避免覆盖容器内的Python可执行文件或符号链接。

内容的提问来源于stack exchange，提问作者Florent