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 sometimes need to see what happens in a few days or months later. Is it possible in docker? I read that if I change date in container, date will get changed on the host system. But it is a bad idea for me. I need to have a few instances of this application on one server and have possibilities of setting up different time for each instance.

But when I try to change date inside the container I get the error:

sudo date 04101812
date: cannot set date: Operation not permitted
Fri Apr 10 18:12:00 UTC 2015

Answer 1

The solutions shown using libfaketime didn't quite work for me using an ARM Mac to run debian-based images

• the x64 image trajano/alpine-libfaketime provides a file that is not compatible with aarm64
• Running make after cloning the the source repo didn't work in Debian

Luckily, libfaketime is available via apt-get on Debian, so I simply took my third-party image, installed libfaketime, and set the LD_PRELOAD variable. Here was the new dockerfile I created:

FROM <upstream image>
RUN apt-get update && apt-get install -y libfaketime
ENV LD_PRELOAD=/usr/lib/aarch64-linux-gnu/faketime/libfaketime.so.1

The path for libfaketime.so.1 will depend on the architecture of <upstream image>, but you can find it by running dpkg -L libfaketime from inside the container.

Then I just passed the FAKETIME environment variable in and everything worked.

Answer 2

If you want to change the date of a container, you would need to relax security on your container by adding the --cap-add SYS_TIME flag to your container at startup.

ie:

docker run --rm -it --cap-add SYS_TIME alpine date -s 2020-08-25

This will provide you more permissions on the container, without need be a root.

Here's a link for reference

You can also do this in kubernetes:

apiVersion: v1
kind: Pod
metadata:
  name: hello-world
spec:
spec:
  containers:
  - name: friendly-container
    image: "alpine:3.4"
    command: ["/bin/echo", "hello", "world", "date -s 2020-08-25"]
    securityContext:
      capabilities:
        add:
        - SYS_TIME

Answer 3

My solution: I run docker on top of a virtualbox vm via vagrant.

This is not as complex as it sounds. The Vagrantfile below resets the datetime of the vm to a specific one, before the machine goes up. The corresponding docker-compose provisioner takes care of automatically running the docker-compose.yml.

Vagrantfile:

Vagrant.configure("2") do |config|
  config.vm.define "ubuntuvm" do |ubuntuvm|
    config.vm.box = "ubuntu/focal64"
    config.vm.provision :docker

    ubuntuvm.trigger.before :up do |trigger|
      trigger.info = "changing time"
      trigger.ruby do |env,machine|
        require 'time'
        machineTime = "2022/07/02 00:20:00"
        offset = DateTime.parse(machineTime).strftime("%Q").to_i - DateTime.now.strftime("%Q").to_i
        puts "Updating machine time to: #{machineTime} by shifting biossystemtime #{offset} ms"
        puts `VBoxManage setextradata #{machine.id} "VBoxInternal/Devices/VMMDev/0/Config/GetHostTimeDisabled" 1`
        puts `VBoxManage modifyvm #{machine.id} --biossystemtimeoffset #{offset}`
      end
    end
  end


  config.vm.hostname = "ubuntuvm"
  # config.vm.network "forwarded_port", guest: 80 host: 8080
  # config.vm.synched_folter "../data"", "/vagrant_data"

  config.vm.provider "virtualbox" do |vb|
      # vb.memory = "1024"
  end
  config.vm.provision :docker_compose, yml: "/vagrant/docker-compose.yml", rebuild: true, run: "always"
end

Then I just need to do a the following:

# start the machine and run the docker-compose
vagrant up

Everytime I start the machine I see the messages:

ubuntuvm: Updating machine time to: 2022/07/02 00:20:00 by shifting biossystemtime -212710744 ms
ubuntuvm: Running docker-compose up...

other commands:

# get inside the machine with ssh to check its time and also check the container's time (docker commands already exist inside there due to the provisioner).
vagrant ssh ubuntuvm
# stop the machine
vagrant halt
# destroy the machine
vagrant destroy

prerequisites

• install virtualbox
• install vagrant
• Install docker-compose provisioner (optional for using docker-compose instead of just docker)

Known issues:

On the first run only, vagrant up will fail to update the time because for some reason the before-up trigger is executed even before the machine is created. On all other executions the machine is already there, so the time is reset as expected.

Answer 4

docker exec -it [Container Id] /bin/bash (exec into container)

rm /etc/localtime (see time zone)

ln -s /usr/share/zoneinfo/Asia/Karachi /etc/localtime (set new time zone)

Answer 5

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 trajano / alpine-libfaketime | Github and the docker image is in trajano/alpine-libfaketime | dockerhub

I also created a variant of it based on Ubuntu: trajano / ubuntu-faketime | Github

Answer 6

I was having the same problem with my jenkins docker instance following steps fixed my problem

1. exec into container

   docker exec -it 9d41c699a8f4 /bin/bash

2. See time zone cat /etc/timezone : out put Etc/UTC

3. set new time zone, with nano : Asia/Colombo (your timezone here)

4. Restart the container

Answer 7

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*().

Answer 8

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())

Answer 9

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:

• You can restart docker.
• You can change the date of your host machine

Steps:

1. Stop your containers.
2. Change the date of your machine via the Date & Time Preferences
3. Restart docker.
4. Start your containers.

Run this sequence again to get back to the right date & time.

OPTION 2: Change the date of the Alpine VM

Use this when:

• You can't restart docker.
• You can't set the date of your host machine

Steps:

1. screen ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/tty
   • The screen starts blank, hit enter a few times.
2. date -s [hh:mm]
   • All of your docker containers will now have your new time. You can also use other formats, look for documentation on “busybox date” as it’s not quite the same as other date implementations.
3. To exit hit control-a : and type d
   • This detaches the screen session, but leaves the tty running.

To reset the time:

1. screen -r
   • This resumes your tty.
2. ntpd -q
   • This uses the server defined in /etc/ntp.conf (this looks like a magic bridge back to the host clock)
3. To exit hit control-a : and type quit
   • This terminates your screen and tty session.

Answer 10

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!