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cron job won't run into my Docker container launched by Visual Studio

since a couple of days I’m trying to create a simple docker that uses cron to execute a scheduled job. I’ve read almost every post found on google but I’m still stucked.

This is my Dockerfile:

FROM mcr.microsoft.com/dotnet/runtime:8.0 AS base
RUN apt-get update
RUN apt-get clean # reduce image size
RUN apt-get install -yqq cron

COPY ["DockerWorkerServiceScheduledExecutable2/cron.allow", "/etc/"]
COPY ["DockerWorkerServiceScheduledExecutable2/mycronjob", "/etc/cron.d/"]

RUN sed -i 's/r$//' /etc/cron.allow
RUN chown -R root:crontab /etc/cron.allow
RUN chmod 0644 /etc/cron.allow
RUN sed -i 's/r$//' /etc/cron.d/mycronjob
RUN chmod 0644 /etc/cron.d/mycronjob

RUN crontab /etc/cron.d/mycronjob
RUN touch /var/log/cron.log
CMD /etc/init.d/crond start
CMD /etc/init.d/cron start && tail -f /var/log/cron.log
CMD /usr/sbin/cron -f
CMD cron

USER app
WORKDIR /app

FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
ARG BUILD_CONFIGURATION=Release
WORKDIR /src
COPY ["DockerWorkerServiceScheduledExecutable2/DockerWorkerServiceScheduledExecutable2.csproj", "DockerWorkerServiceScheduledExecutable2/"]
RUN dotnet restore "./DockerWorkerServiceScheduledExecutable2/./DockerWorkerServiceScheduledExecutable2.csproj"
COPY . .
WORKDIR "/src/DockerWorkerServiceScheduledExecutable2"
RUN dotnet build "./DockerWorkerServiceScheduledExecutable2.csproj" -c $BUILD_CONFIGURATION -o /app/build

CMD /etc/init.d/cron start && tail -f /var/log/cron.log
CMD /usr/sbin/cron -f

This is my cron.allow, that I used trying to register the job for the user "app" with RUN crontab -u app /etc/cron.d/mycronjob, but I think it’s not needed anymore given that I tried to register the job to the root user

root
app

And this is the file "mycronjob"

*/1 * * * * dotnet /app/bin/Debug/net8.0/DockerWorkerServiceScheduledExecutable2.dll >> /var/log/cron.log 2>&1

Last one, this is the Program.cs of the DockerWorkerServiceScheduledExecutable2 project

if (!File.Exists("myfile.txt"))
{
    File.Create("myfile.txt").Close();
}
await File.AppendAllTextAsync("myfile.txt", "DoSomethingUseless: " + DateTime.Now.ToString("dd/MM/yyyy hh:mm:ss") + System.Environment.NewLine + "rn");
Console.WriteLine("DoSomethingUseless: " + DateTime.Now.ToString("dd/MM/yyyy hh:mm:ss"));

I’m a newbie in the linux and docker world so I made a mess probably(99% sure).
The main effect is that if I check cron service status with service cron status I got "cron is not running … failed!"

I know that (probably) this commands do the same stuff, but I was not sure which one was the right one, which was the right row, and, at the end, none of them seems to works 🙁

CMD /etc/init.d/crond start
CMD /etc/init.d/cron start && tail -f /var/log/cron.log
CMD /usr/sbin/cron -f
CMD cron

Can anyone help me to fix that? Any hint would be appreciated too 🙂
As I said initially tried almost everything found on google, I’d like to see my useless message added to the file

thank you

Sergio

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    I have made a step forward, the problem seems to be the "starting image", sorry if I use the wrong name but I don't know how to call it:

    FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build

    this is my new Dockerfile that almost does what I want:

    FROM ubuntu:latest
MAINTAINER [email protected]

RUN apt-get update && apt-get -y install cron && apt-get -y install dotnet8

# Copy hello-cron file to the cron.d directory
# COPY hello-cron /etc/cron.d/hello-cron
COPY ["DockerWorkerServiceScheduledExecutable3/mycronjob", "/etc/cron.d/mycronjob"]
RUN sed -i 's/r$//' /etc/cron.d/mycronjob
# Give execution rights on the cron job
RUN chmod 0644 /etc/cron.d/mycronjob

# Apply cron job
RUN crontab /etc/cron.d/mycronjob
 
# Create the log file to be able to run tail
RUN touch /var/log/cron.log
 
# Run the command on container startup
# CMD cron && tail -f /var/log/cron.log
CMD service cron start && tail -f /var/log/cron.log

WORKDIR /app

# FROM mcr.microsoft.com/dotnet/sdk:8.0 AS build
ARG BUILD_CONFIGURATION=Release
WORKDIR /src
COPY ["DockerWorkerServiceScheduledExecutable3/DockerWorkerServiceScheduledExecutable3.csproj", "DockerWorkerServiceScheduledExecutable3/"]
RUN dotnet restore "./DockerWorkerServiceScheduledExecutable3/./DockerWorkerServiceScheduledExecutable3.csproj"
COPY . .
WORKDIR "/src/DockerWorkerServiceScheduledExecutable3"
RUN dotnet build "./DockerWorkerServiceScheduledExecutable3.csproj" -c $BUILD_CONFIGURATION -o /app/build

    Now the problem is that cron doesn't start automatically, I have to run

    service cron start

    to make it working


  2. 0

    another step 😀
    to make the cron starts at startup I had to create the file "docker-compose.vs.debug.yml" in the same directory of "docker-compose.yml" and add this:

    version: '3.4'

services:
  dockerworkerservicescheduledexecutable3:
    image: ${DOCKER_REGISTRY-}dockerworkerservicescheduledexecutable3
    build:
      context: .
      dockerfile: DockerWorkerServiceScheduledExecutable3/Dockerfile
    entrypoint: sh -c '/etc/init.d/cron start && tail -f /var/log/cron.log'

    in this way in Debug mode it works as hoped.
    Now I have to face the Release mode

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