Is it possible change date in docker container?

Question

I have a container with a running program inside tomcat. I need to change date only in this container and test my program behaviour. I have time sensitive logic, and sometim

Answer 1

It is very much possible to dynamically change the time in a Docker container, without effecting the host OS.

The solution is to fake it. This lib intercepts all system call programs use to retrieve the current time and date.

The implementation is easy. Add functionality to your Dockerfile as appropriate:

WORKDIR /
RUN git clone https://github.com/wolfcw/libfaketime.git
WORKDIR /libfaketime/src
RUN make install

Remember to set the environment variables LD_PRELOAD before you run the application you want the faked time applied to.

Example:

CMD ["/bin/sh", "-c", "LD_PRELOAD=/usr/local/lib/faketime/libfaketime.so.1 FAKETIME_NO_CACHE=1 python /srv/intercept/manage.py runserver 0.0.0.0:3000]

You can now dynamically change the servers time:

Example:

def set_time(request):
    import os
    import datetime
    print(datetime.datetime.today())
    os.environ["FAKETIME"] = "2020-01-01"  #  string must be "YYYY-MM-DD hh:mm:ss" or "+15d"
    print(datetime.today())