Cron 作业在 ubuntu Docker 容器中不起作用

Question

我正在构建一个 docker 镜像来安排 Azure azcopy 作业。为了检查 cron 调度是否有效，我开始创建以下 Dockerfile：

FROM ubuntu:20.04

# Updating packages and installing cron, wget and curl
RUN apt-get update && apt-get -y upgrade \
    && apt-get install -y cron \
    && apt-get install -y wget \
    && apt-get -y install curl

# Create directories in the home of the root user
RUN mkdir -p /root/Downloads && mkdir -p /root/bin && mkdir /root/scripts

WORKDIR /root/Downloads

# Download and extract azcopy binary 
RUN wget -O azcopy_v10.tar.gz https://aka.ms/downloadazcopy-v10-linux \
    && tar -xf azcopy_v10.tar.gz --strip-components=1

# Copy the azcpoy binary to the root user bin directory    
RUN cp azcopy /root/bin

# Add the root user bin directory to the shell path
ENV PATH="$PATH:/root/bin"

# Change working directory to the location were scripts are stored
WORKDIR /root/scripts

# Copy the azcopy script to the root user script directory and give proper permissions
COPY ./scripts/azcopy_script.sh .
RUN chmod 777 azcopy_script.sh

# Copy the crontab to the cron.d directory, give appropiate permissions and run it
COPY crontab /etc/cron.d/azcopy_cron_file
RUN chmod 777 /etc/cron.d/azcopy_cron_file && crontab /etc/cron.d/azcopy_cron_file && service cron restart

# Create entrypoint for cron
ENTRYPOINT ["cron", "-f"]

crontab的内容是：

* * * * * root /bin/bash /root/scripts/azcopy_script.sh

azcopy_script.sh的内容是：

#!/bin/bash
echo "This is a test line printed on: $(date)"  >> "/root/test_output.txt"

每分钟都应在

"/root/test_output.txt"

后附加一个新行，但不会创建文件。如果我在容器中启动交互式 shell 会话并手动运行文件，它工作正常。

cron 作业也列在容器中：

root@4bc9565fd3ff:~# crontab -l
* * * * * root /usr/bin/bash /root/scripts/azcopy_script.sh

如果我通过运行

* * * * * root /usr/bin/bash /root/scripts/azcopy_script.sh

将行

crontab -e

添加到根用户 crontab，作业会运行。

Answer 1

（将

/usr/bin/bash

更改为

/bin/bash

，问候）