See cron log ouput with docker logs

cron-tab-docker-logs.txt

1. Alpine (No need for redirection)

using the default cron utility (busybox)

## Dockerfile
=====
FROM alpine:3.7

# Setting up crontab
COPY crontab /tmp/crontab
RUN cat /tmp/crontab > /etc/crontabs/root


CMD ["crond", "-f", "-l", "2"]
=====

## Crontab
=====
* * * * * echo "Crontab is working - watchdog 1"
=====

2. Centos
Redirection to /proc/1/fd/1 inside the crontab declaration line

## Dockerfile
=====
FROM centos:7

RUN yum -y install crontabs

ADD crontab /etc/cron.d/crontab
RUN chmod 0644 /etc/cron.d/crontab
RUN crontab /etc/cron.d/crontab


CMD ["crond", "-n"]
=====

## Crontab
=====
* * * * * echo "Crontab is working - watchdog 1" > /proc/1/fd/1
=====


=> Test show cron ouput with docker logs {container_name}