Docker容器启动后Cron服务无法运行，容器自动退出求助

报错信息 #

docker: Error response from daemon: OCI runtime create failed: container_linux.go:380: starting container process caused: exec: "cron": executable file not found in $PATH: unknown.

我的Dockerfile内容 #

# Pull base image.
FROM amazonlinux:2

ARG TERRAFORM_VERSION=1.2.6

RUN \
yum update -y && \
yum install unzip -y && \
yum install wget -y && \
yum install vim -y \
yum install bash -y

################################
# Install Terraform
################################

# Download terraform for linux
RUN wget https://releases.hashicorp.com/terraform/${TERRAFORM_VERSION}/terraform_${TERRAFORM_VERSION}_linux_amd64.zip

RUN unzip terraform_${TERRAFORM_VERSION}_linux_amd64.zip

RUN mv terraform /usr/local/bin/


################################
# Install python
################################

RUN yum install -y python3-pip
RUN pip3 install --upgrade pip


################################
# Install AWS CLI
################################
RUN pip install awscli --upgrade --user

# add aws cli location to path
ENV PATH=~/.local/bin:$PATH


RUN mkdir ~/.aws && touch ~/.aws/credentials


################################
# Install Cron
################################

RUN yum -y install ca-certificates shadow-utils cronie && yum -y clean all

# Creating crontab
COPY  ./automation.sh /var/automation.sh


# Giving executable permission to script file.
RUN chmod +x /var/automation.sh \
    && echo "* * * * *  /bin/bash /var/automation.sh" >> /var/crontab


# Ensure sudo group users are not asked for a password
RUN echo '%sudo ALL=(ALL) NOPASSWD:ALL' >> \
/etc/sudoers

#run cron process through cmd

CMD ["cron", "-f"]

问题原因与解决方法 #

核心原因 #

Amazon Linux 2中安装cronie后，cron的可执行文件是/usr/sbin/crond，而非cron，你指定的启动命令cron不存在，导致容器启动失败；同时Dockerfile中还有几处语法和配置问题需要修正。

具体修复步骤 #

1. 修正Cron启动命令
   将CMD ["cron", "-f"]改为CMD ["/usr/sbin/crond", "-n"]，-n参数让crond在前台运行，保证容器不会因为后台进程退出而停止。

2. 修复yum安装命令的语法错误
   原Dockerfile中安装vim的行末尾缺少&&，导致bash执行报错，修改为：

   RUN \
   yum update -y && \
   yum install unzip -y && \
   yum install wget -y && \
   yum install vim -y && \
   yum install bash -y
   

3. 修正crontab任务加载问题
   你把任务写到/var/crontab，但默认crond不会自动加载该文件，可选择以下两种方式之一：

   • 将任务添加到系统crontab：

     RUN echo "* * * * *  /bin/bash /var/automation.sh" >> /etc/crontab
     

   • 将任务添加到root用户的任务列表：

     RUN echo "* * * * *  /bin/bash /var/automation.sh" | crontab -
     

4. 修复PATH环境变量解析问题
   ENV指令中~不会被解析为用户家目录，需替换为绝对路径：

   ENV PATH=/root/.local/bin:$PATH
   

修正后的完整Dockerfile示例 #

# Pull base image.
FROM amazonlinux:2

ARG TERRAFORM_VERSION=1.2.6

RUN \
yum update -y && \
yum install unzip -y && \
yum install wget -y && \
yum install vim -y && \
yum install bash -y

################################
# Install Terraform
################################

RUN wget https://releases.hashicorp.com/terraform/${TERRAFORM_VERSION}/terraform_${TERRAFORM_VERSION}_linux_amd64.zip
RUN unzip terraform_${TERRAFORM_VERSION}_linux_amd64.zip
RUN mv terraform /usr/local/bin/

################################
# Install python
################################

RUN yum install -y python3-pip
RUN pip3 install --upgrade pip

################################
# Install AWS CLI
################################
RUN pip install awscli --upgrade --user
ENV PATH=/root/.local/bin:$PATH

RUN mkdir /root/.aws && touch /root/.aws/credentials

################################
# Install Cron
################################

RUN yum -y install ca-certificates shadow-utils cronie && yum -y clean all

COPY ./automation.sh /var/automation.sh
RUN chmod +x /var/automation.sh
RUN echo "* * * * *  /bin/bash /var/automation.sh" | crontab -

RUN echo '%sudo ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers

CMD ["/usr/sbin/crond", "-n"]

内容的提问来源于stack exchange，提问作者Devops-Learner