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I've created a docker container, which is running in the wrong timezone. I personally need it to run in my timezone (Europe/Stockholm, GMT+1). Since the project is open source, other users may also wish to change that. I wish to make it easy for anyone to change this in e.g. the Dockerfile or in the docker-compose.yml.

If possible, I also wish that the solution is applicable not only on CentOS in case someone wishes to use a different distro.

What is the most distro-agnostic approach to set the localtime/timezone in my docker container?

These two approaches seem to be common but I'm not sure if they are really the best way forward for me:

TZ environment variable

Some Linux distros read the TZ environment variable. However, I'm noticing it doesn't work when I use the centos:7 image.

/etc/localtime

You can map the container's /etc/localtime to /etc/localtime on the host in the docker-compose.yml. But when doing this, distros that use /etc/timezone is left at UTC and software which may be reading that will then read the wrong timezone.

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  • /etc/localtime is the ultimate fallback location. I don’t understand your last paragraph on it, though. It’s a symlink in most cases. Copying the actual file to the container should produce the desired result. – Daniel B May 16 '16 at 11:32
  • @DanielB I meant that even if you take care of /etc/localtime it seems some software rely on /etc/timezone. So therefore I was wondering if the /etc/localtime approach was really the best one. – fredrik May 16 '16 at 11:35
  • I guess that software needs to be fixed, then. /etc/localtime is available virtually everywhere, including OS X and FreeBSD. – Daniel B May 16 '16 at 11:43
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    Some distros like: RUN echo "Europe/Stockholm" > /etc/timezone Others like: RUN ln -s /usr/share/zoneinfo/Europe/Stockholm /etc/localtime – joat Sep 9 '16 at 2:19
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Distro-agnostic would require a script that detects which distro is being used. This is because each distro "family" has a different way of noting timezones. For some, adding the following to the Dockerfile might work:

RUN echo "Europe/Stockholm" > /etc/timezone

Other (e.g., Debian) require using the above and then following with another Dockerfile command like:

RUN RUN sudo dpkg-reconfigure -f noninteractive tzdata

Other distros (IIRC, including CentOS) would require something like:

RUN ln -s /usr/share/zoneinfo/Europe/Stockhom /etc/localtime

Making it distro-agnostic would require researching each distro's method for re-configuring the timezone. If you look at /etc/localtime, you'll notice that it's not a text file.

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  • And some applications ignore the OS timezone setting anyway :-7. e.g. jenkins is java based, you need to pass some java arguments to set timezone in the jenkins service/start script. So Distro-agnostic and App-agnostic would have to cover more scenarios than just /etc/localtime and /etc/timezone – gaoithe Jan 22 '19 at 17:41

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