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
That's not possible with Docker. Docker uses the same clock as the outside kernel. What you need is full virtualization which emulates a complete PC.
The sudo
fails because it only makes you root
of the virtual environment inside of the container. This user is not related to the real root
of the host system (except by name and UID) and it can't do what the real root
could do.
If you use a high level language like Python or Java, you often have hooks where you can simulate a certain system time for tests or you can write code which wraps "get current time from system" and returns what your test requires.
Specifically for Java, use joda-time. There you can inject your own time source using DateTimeUtils.setCurrentMillis*()
.
I was having the same problem with my jenkins docker instance following steps fixed my problem
exec into container
docker exec -it 9d41c699a8f4 /bin/bash
See time zone
cat /etc/timezone
: out put Etc/UTC
set new time zone, with nano : Asia/Colombo (your timezone here)
Restart the container
This worked for me, maybe you could try it:
dpkg-reconfigure tzdata
Edit: Execute it inside the container you are having problems. An interface will appear. There you can edit the timezone and localtime for example, and set it correctly, that fixed my problem, that was the same as yours.
Good luck!
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())
For me, I actually needed to set the actual date for testing. I found the following options work on Mac, but you have to realize you'll be changing the date for all of your containers because you're changing the date of the underlying Alpine VM that Docker uses for all of its containers.
OPTION 1: Change the date of your host machine & restart docker
Use this when:
Steps:
Run this sequence again to get back to the right date & time.
OPTION 2: Change the date of the Alpine VM
Use this when:
Steps:
screen ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/tty
date -s [hh:mm]
control-a :
and type d
To reset the time:
screen -r
ntpd -q
control-a :
and type quit
I created a Docker image containing libfaketime for use with Alpine but the process can be done in other distributions.
Here's an example of using it Java using Groovy as an example. But Tomcat can be used as well.
FROM groovy:alpine
COPY --from=trajano/alpine-libfaketime /faketime.so /lib/faketime.so
ENV LD_PRELOAD=/lib/faketime.so \
DONT_FAKE_MONOTONIC=1
Then build and pass the FAKETIME
environment variable when doing a docker run for example
docker build -f fakedemo-java.Dockerfile . -t fakedemo
docker run --rm -e FAKETIME=+15d fakedemo groovy -e "print new Date();"
Source is in https://github.com/trajano/alpine-libfaketime and the docker image is in https://hub.docker.com/r/trajano/alpine-libfaketime
I also created a variant of it based on Ubuntu https://github.com/trajano/ubuntu-faketime