How to set system time dynamically in a Docker container

Question

Is there any way to set a Docker containers system time dynamically (at run time) without effecting the host machine?

Using

hwclock --set --date "Sat Aug 17 08:31:24 PDT 2016"

gives the following error:

hwclock: Cannot access the Hardware Clock via any known method.
hwclock: Use the --debug option to see the details of our search for an access method.

Using

date -s "2 OCT 2006 18:00:00"

gives the following error:

date: cannot set date: Operation not permitted

Use case:

I need to test time sensitive software (behaviour depends on the date).

Other common use cases:

running legacy software with y2k bugs
testing software for year-2038 compliance
debugging time-related issues, such as expired SSL certificates
running software which ceases to run outside a certain timeframe
deterministic build processes.

https://stackoverflow.com/questions/29556879/is-it-possible-change-date-in-docker-container — dawud, Jan 06 '17 at 14:03
Actually, I just found and positively tested a solution using the libfaketime https://github.com/wolfcw/libfaketime I'll update with an answer + working example shortly. — Vingtoft, Jan 06 '17 at 14:12

Vingtoft · Accepted Answer · 2018-06-14T21:21:59.790

32

It is possible

The solution is to fake it in the container. 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:

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

edited Jun 14 '18 at 21:21

answered Jan 09 '17 at 12:48

Vingtoft

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For others coming to this solution, be aware that this will not work for golang applications or other statically linked exes. – Sentinel Oct 16 '18 at 11:38
7

Thanks @Sentinel. Funnily enough, I just found this answer via google, I specifically want to use it with a golang app, and I noticed that you left this comment on a 1.5-years-old question just 2 hours ago. Feels like it was for me. Thanks! :) – dimonomid Oct 16 '18 at 13:42
Why does is not work in your situation? Does Golang not use system calls to retrieve time? @dimonomid I suggest you give it a try, it’s quick to implement the solution. – Vingtoft Oct 16 '18 at 14:02
1

@Vingtoft Let me know if it does in fact work, but search around. Golang doesn't dynamically link in the libraries. – Sentinel Oct 16 '18 at 16:06
1

@dimonomid Yeah I was pretty disappointed. More disappointed with Docker actually. I need to implement timing related tests. This makes Docker pretty much useless as a "container". I would have thought intercepting system time calls for timezone sync would have been item 1 on the Docker agenda. Apparently not. – Sentinel Oct 16 '18 at 16:07
I get the error: ERROR: ld.so: object '/usr/local/lib/faketime/libfaketime.so.1' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS64): ignored. – Vikram Dattu May 27 '20 at 04:22

Benyamin Jafari · Answer 2 · 2021-09-08T16:32:05.963

2

Here's docker-compose solution:

Add /etc/localtime:/etc/localtime:ro to the volumes attribute.

Check this link for getting an example.

edited Sep 08 '21 at 16:32

answered Aug 21 '18 at 05:53

Benyamin Jafari

213
2
5

This is exactly *not* what the question is asking for. You can't use this to dynamically change the time inside the container. – Herohtar Apr 28 '22 at 20:05

score 0 · Answer 3 · edited Jan 06 '17 at 13:34

0

Start the container with an additional environment variable:

docker run -e "SET_CONTAINER_TIMEZONE=true" \
           -e "CONTAINER_TIMEZONE=US/Arizona" [docker image name]

edited Jan 06 '17 at 13:34

dawud

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answered Jan 06 '17 at 12:57

13dimitar

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Im looking for a way to set the time dynamically, meaning it can be set at runtime. I have updated my question. – Vingtoft Jan 06 '17 at 13:14

How to set system time dynamically in a Docker container

3 Answers3