Docker容器启动失败：exec: 'python3 app.py'不在$PATH中求排查

问题详情 #

未在Dockerfile中指定PATH环境变量，但容器启动时多次出现runc创建失败，报错提示无法找到可执行文件，相关信息如下：

Dockerfile内容 #

# Set the base image to Python 3.9
FROM python:3.9

# Set the working directory to /app
WORKDIR /app

# Copy the current directory contents into the container at /app
COPY . /app

# Install any needed packages specified in requirements.txt
RUN pip3 install --trusted-host pypi.python.org -r requirements.txt

# Set environment variables
ENV SLACK_WEBHOOK_URL ${SLACK_WEBHOOK_URL}

# Make port 80 available to the world outside this container
EXPOSE 80

# Run app.py when the container launches
CMD ["python3", "app.py"]

部署日志片段 #

[5/Oct/2023:11:05:30] [deployment:16] Finalizing your deployment
[5/Oct/2023:11:05:45] [deployment:17] Creating your deployment
[5/Oct/2023:11:09:11] runc create failed: unable to start container process: exec: "python3 app.py": executable file not found in $PATH
[5/Oct/2023:11:09:34] [deployment:17] Node crashed; container "app": CannotStartContainerError: ResourceInitializationError: failed to create new container runtime task: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: exec: "python3 app.py": executable file not
[5/Oct/2023:11:10:04] [deployment:17] Started 1 new node
[5/Oct/2023:11:10:36] [deployment:17] Took too long
[5/Oct/2023:11:10:44] runc create failed: unable to start container process: exec: "python3 app.py": executable file not found in $PATH

排查与解决方法 #

1. 核心原因分析 #

报错显示容器将python3 app.py作为单一可执行文件名去PATH中查找，而非将python3作为命令、app.py作为参数执行。这通常是因为启动命令被错误解析为单一字符串，而非分拆的参数列表。

2. 具体修复方案 #

• 调整Dockerfile的CMD格式
  将数组格式的CMD改为shell格式，让容器通过shell解析命令：

  CMD python3 app.py
  

  或者利用官方Python镜像的默认配置（python已关联到python3），改用：

  CMD ["python", "app.py"]
  

• 检查部署平台的启动命令配置
  若部署平台允许自定义启动命令，确保输入的是分拆的参数（如python3和app.py分别作为两个独立字段），而非合并为python3 app.py单一字符串。

• 验证文件与路径正确性
  在Dockerfile中添加验证步骤，确认文件和路径无误：

  RUN ls -l /app  # 确认app.py存在于工作目录
  RUN which python3  # 确认python3已在PATH中
  

内容的提问来源于stack exchange，提问作者Azizul Haque